10
Vertebrates
10.1 Introduction
In forensic biology, vertebrates are as much the victims of crimes as sources of evidence used to solve them (Figure 10.1). Police forces often have special units assigned to deal with such incidents. For example, in the UK, there is the UK National Wildlife Crime Unit that works in partnership with the police forces at both a national and international level and currently undertakes about 200 investigations a year. Table 10.1 provides a summary of the many ways in which vertebrates are involved in criminal investigations.
Figure 10.1 Dead badger (Meles meles) found by the side of the road. In the UK, the culling of badgers is controversial. Sometimes badgers are illegally shot (or killed in badger baiting) and the corpses left by the roadside. This gives the impression that they were killed by traffic and the badger population is larger than it actually is. A vehicle killed this badger and disturbed soil around the body indicates it had been digging for worms by the roadside. Although tuberculosis is common in UK badgers and often causes lesions in the lungs, the majority do not exhibit clinical signs. There is a small risk of disease transfer to humans, therefore handle dead and injured badgers carefully to minimise risk.
Table 10.1 Summary of vertebrate animals and their forensic relevance.
| Animal | Forensic relevance |
| Dogs | Cause of human injury or death Cause of traffic accident Victim of neglect or abuse Use in illegal baiting or dog fighting ‘Kidnapping’ – pets, especially dogs, are sometimes stolen and held for ransom Doping (e.g. greyhound racing) Drug ‘mules’ Cause of post‐mortem damage Source of DNA linking a person to a locality |
| Cats | Cause of traffic accident Victim of neglect or abuse Use in illegal baiting Source of DNA linking a person to a locality |
| Rats and other rodents | Cause of human injury Cause of post‐mortem damage to flesh and bones Food spoilage |
| Domestic livestock | Victim of neglect or abuse Rustling Fraud (e.g. illegal movements across borders) |
| Birds | Cause of post‐mortem damage Victim of neglect or abuse Illegal trade in protected species Illegal killing of protected species |
| Fish | Cause of post‐mortem damage Fraud (e.g. mislabelling) Illegal trade in protected species |
| Wild mammals, reptiles and amphibians | Illegal trade in protected species Illegal killing of protected species Poaching |
10.2 Identification of Vertebrates
Sometimes it is only necessary to identify animals to species level – for example, to determine whether a protected species is included among a group of legally traded common species. Species identification is also required to determine whether animal products are mislabelled or adulterated. For example, in Europe there are regular reports of horsemeat sold as beef (Premanandh 2013). Fraudulent mislabelling is not a minor issue that is the preserve of the local food standards agency. Large‐scale fraud is often linked to organised criminal gangs and it can lead to societal conflict. This is because some religions have strict dietary rules about which animals (if any) may be consumed. For example, in 2017 in the northern Indian state of Haryana, the police collected samples of meat from households and businesses, particularly in Muslim districts, to ensure that it was not beef. Cows are considered sacred in the Hindu region and many states in India forbid the slaughter of cows or the consumption of beef, or both.
At other times, it is necessary to identify an individual animal with a high degree of certainty, such as when a dog fatally mauls a child. Vertebrate identification techniques can be divided into three broad categories: physical techniques, molecular techniques and chemical techniques. Physical techniques rely on observations of the animal's characteristic features, its droppings, or of man‐made artefacts, such as brands and tracking devices. Molecular techniques involve sequencing of the animal's genome and these have largely replaced older methods based on protein electrophoresis and immunological techniques. Chemical techniques involve analysing an animal's chemical composition. In some instances, chemical analyses can indicate species identity, whilst others provide evidence of geographical origin and whether a specimen is wild or captive‐bred.
10.2.1 Identification of Mammals from their Morphology
Although 5416 species of mammal have been described, some authors think that many more still await discovery and the true number of species is closer to 7000. Whether living or recently dead, mammals can usually be identified to species from their gross morphology. Once skeletonised, many remain easy to identify to species level if one has the skull or the teeth (Figure 10.2). For example, members of the families Canidae (dogs) and Felidae (cats) have large conical canines and sharp carnassial teeth for slicing through meat, whilst members of the Bovidae (sheep, cattle, antelopes) usually lack canines and have block‐like molars used in a side‐to‐side motion for grinding. However, if there are only a few of the smaller bones available, then identification may be limited to genus or family level. Once an animal is processed for food, it is virtually impossible to identify it from morphological characteristics.
Figure 10.2 Confiscated orang‐utan (Pongo pygmaeus) skull. Orang‐utans are CITES Appendix I listed and trade in living animals and their body parts is prohibited. The skull was carved and then blackened to appear antique. The dentition and skull dimensions make this specimen easy to identify.
For domestic animals, it may be necessary to identify the breed. For example, within some legislatures, certain types of dog are banned from public ownership owing to their propensity for aggression and use in illegal dog fighting. American Pit Bull terriers are banned in the UK, whilst Rottweilers are legal in the UK but banned in some US states. Even veterinary surgeons and dog shelter staff make mistakes when asked to identify pit bulls solely on their appearance (e.g. Olson et al. 2015). Although DNA tests can identify dog breeds, the extent to which a breed is considered ‘pure’ varies owing to cross‐breeding. Some types of dog, such as ‘pit bulls’, are actually a mixed group and not even recognised as a breed.
Identifying an individual mammal on morphological evidence presents serious difficulties. For example, a dog or other animal responsible for an attack or for causing an accident that runs away afterwards would be difficult to identify later solely based on witness statements. Most people, when asked to describe a dog, would be unable to provide more than a vague description. Statements such as ‘it was a large brown Labrador and the accused is also a large brown Labrador’ are not going to be much use as evidence in a court of law.
10.2.1.1 Identification of Domestic Animals
Farm animals, such as cattle and horses, are often branded to identify ownership and this may include an individual number. Freeze branding is more humane than hot iron branding and results in white hairs growing at the brand site rather than those of the normal colour. Freeze branding can be used on fish and results in the scales changing colour. Branding is cheap, permanent, and impossible to conceal or shave away. Unfortunately, the effectiveness of branding is often compromised by poor record‐keeping and difficulties in transmitting information between interested parties. Therefore, branding is less effective than microchipping for identification (Campe et al. 2016). In addition, once the animal is slaughtered and skinned, the means of identification is lost.
In the past, many farmers used to notch the ears of their livestock. Each farm in an area had its own unique pattern. The practice still takes place on a local level, but ear notches can only indicate the farm where the animal was raised. Many farm animals in the UK and Europe are required by law to have identifying ear tags and there is a variety of tags in use, depending upon the type of animal. Ear tags enable an animal to be identified as an individual and its movements traced throughout its life.
Unfortunately, ear tags are easy to remove and replace. This facilitates rustling and the fraudulent movement of cattle within and between countries. To many members of the public, cattle rustling is something that only happens in Hollywood westerns. However, it is actually a major criminal activity in both the developed and developing world. For example, in the UK in 2014, there were 88 691 livestock animals stolen (predominantly in Northern Ireland) and this represented a loss of about £6.6 million to the farming community. In parts of Africa, cattle rustling is increasingly associated with violent organised crime: in Kenya alone, 580 people were killed in cattle raids between 2012 and 2014. The ability to identify domestic livestock quickly and accurately is therefore an important part of tackling this criminal activity.
Pets, high‐value farm animals, and protected species of wild animals (e.g. rhinos) can have a microchip (transponder) injected underneath the skin, which provides a unique identifying 15‐digit number. Indeed, in the UK, it is a legal requirement that all dogs are microchipped. The chip is detectable using a special scanning device (transceiver) and the output compared to a database. Microchipping helps reunite strayed pets with their owners, but is also useful in combatting the thriving trade in stolen dogs. In the UK in 2015, the police were informed of 1776 cases of dogs being stolen. Organised criminal gangs steal certain breeds to order for shipping overseas, as well as for ransom or use as ‘bait dogs’ by dog fighting gangs. Cats are also stolen in increasing numbers: in 2016, there were 261 reports to the police of cats being stolen in the UK and the true figure is probably much higher.
Transponders used in cattle, and other domestic animals raised for their meat, are usually placed externally within ear tags. Injectable transponders are not used with animals destined for human consumption, because of the risk of the transponder migrating from its site of injection and the extra time required in the abattoir to locate it. Although highly effective, the identification of an animal from a microchip requires the presence of the whole animal – alive or dead – and a scanner.
Biometric technology that is used to identify humans is now being adapted for use in animals, although these are still in their early stages of development. For example, facial image databases have been trialled for cattle and horses (Jarraya et al. 2015; Kumar et al. 2016).
10.2.1.2 Hairs as Forensic Indicators
Mammalian hairs are often characteristic of the species or family and can provide information on coat coloration. However, their presence provides only weak evidence of an association with any individual animal, unless supported by other evidence such as DNA. Hairs vary in length and colour between different parts of the body and this should be borne in mind when collecting specimens or interpreting evidence. Animal hairs may also originate from a fur garment or pelt – these hairs are often coloured, trimmed, and lack a root.
Hairs are classified as vibrissae, bristle hairs, guard hairs, over hairs, and under hairs. The vibrissae, or whiskers, occur on the muzzle. In animals, such as rodents, cats, and sea lions, the vibrissae are large and serve a sensory function. Vibrissae are circular and taper to a point at the tip. They tend to have a uniform structure and are seldom used for identification. Bristle hairs are a characteristic feature of domestic pigs and other members of the Suidae. They are short thick hairs that have a forked tip. Guard hairs comprise the majority of hairs on the coats of most mammals and are the most commonly used hairs for identification. Guard hairs tend to be long and coarse and become flattened towards their tip. Over hairs are long stiff hairs that are distributed in small numbers among the guard hairs. Under hairs are short soft hairs that provide insulation and are sometimes used for identification. In most mammals, the under hairs are not seen unless the guard hairs are moved aside, but in domestic sheep the under hairs are extremely long and form the fleece.
Hairs provide identification by a combination of their external and internal features and as a source of DNA. Hairs consist of two portions: the hair root and the hair shaft. The hair root extends beneath the skin surface into the hair follicle and at the base of this is the hair bulb that contains the germinal cells responsible for forming the hair. Variations in the shape of the hair root can provide some degree of identification. For example, in dogs the hair root is spade‐shaped, whilst in humans it is club‐shaped. However, it is the presence of the living germinal cells, and therefore DNA, that offers the best means of identification. Unfortunately, only the old hairs (telogenic hairs) fall out naturally and these do not have their roots attached. These hairs have small bulbs and their DNA is present in low amounts and degraded. To obtain a hair with its root attached, it is necessary to pull the hair out forcibly: the presence of hairs with their roots attached is therefore an indication of a violent altercation.
The structure of a hair is often likened to that of a pencil. There is an innermost medulla (the pencil lead), a thick middle layer called the cortex (the wooden bit), and a thin outermost layer called the cuticle. The size and composition of all three layers provides identifying features (Figure 10.4a–d).
Figure 10.4 Guard hair microstructure. (a) Cow hair, whole mount, (b) dog hair, whole mount, (c) cat hair, scale cast, (d) goat hair, scale cast.
The medulla varies in size and in some species may be absent entirely. If the medulla contains air, it appears black and featureless under the microscope. There is a variety of types of medulla and just a few will be mentioned here. An unbroken medulla is one in which the medulla forms a continuous line along the length of the hair, whilst a broken medulla is one in which there are regions in which the medulla is replaced by the cortex (this is found in several primate species). A ladder medulla is one in which blocks of air spaces are arranged in one or more rows along the length of the hair (e.g. rats and rabbits).
The cortex of the hair is often rather amorphous and contains pigment granules that impart coloration and inclusions such as cortical fusi and ovoid bodies. Apart from its size in relation to the hair width, the cortex is seldom used as an identifying feature.
The cuticle layer consists of a series of overlapping scales. The sizes and shapes of the scales differ considerably between species and this makes them useful for identification. Further distinctions can be made by counting the number of scales across and up the length of a hair. There are two basic types of scales: imbricate scales, in which the scales are arranged like the tiles on a roof and there are several scales across the width of the hair, and coronal scales, in which each scale encircles the width of the hair. Further subdivisions can then be made within each category, based on the position of the scales in relation to the longitudinal axis (longitudinal, transverse, or intermediate) and the shape of the scale margins (smooth, scalloped, dentate, or rippled). Further distinctions can be made according to the type of scale pattern (mosaic, petal, transitional, or wave) and within each pattern it is possible to recognise further subdivisions.
The structure of the medulla and cortex can be observed from whole mounts using a light microscope. Further details can be obtained by making cross‐sections in order to determine the profile of the hair and its component parts. Scanning electron microscopy provides exceptional detail of the scaling pattern and other external features of hairs along with their three‐dimensional shapes, although light microscopy is perfectly adequate for most analysis. In the latter case, place a hair onto a layer of wet nail varnish or lacquer on a glass microscope slide, being careful to leave one end of the hair protruding beyond the varnish to facilitate its removal. Once the varnish is set, gently remove the hair. A cast of the hair’s surface remains in the varnish and this is observable using a light microscope. Jackson and Jackson (2008), provide a thorough guide to the collection and analysis of hair and fibre evidence.
Dogs and cats are two of the most popular pets and as any owner will agree, their hairs get everywhere, despite strenuous efforts to keep rooms and clothing clean. They are therefore a potential source of forensic evidence. For example, they can indicate that a suspect was present in a room or vehicle (dog and cat hairs are often found in the cars of pet owners), indulged in bestiality, or had contact with a particular animal. In cases of sheep worrying, badger baiting, and illegal dog fighting, the hairs of the victim(s) may be found on the muzzle or coat of the accused dog or associated with the property/possessions of the dog's owner. Similarly, in vehicle accidents, animal hairs might be found on the radiator grill, bumper, or elsewhere. In the latter cases, there would be a high chance of finding bloodstains that might yield DNA to support the link. Just as pets and other domestic animals transfer their hairs onto humans, so humans transfer clothes fibres onto their pets, and brushing their fur or coat can yield evidence of contact.
Hair analysis can be particularly useful in cases of fraud and illegal wildlife trade, because it is simple and provides quick and cheap results. For example, parka jackets and other winter clothing often have fur trimmings. Sometimes the fur comes from rabbits, racoon dogs, or mink that are kept in fur farms and sometimes it is synthetic. Fur farms were banned in the UK in 2003 and many retail outlets have fur‐free policies. Despite this, there are frequent instances of clothing that is marketed as being made from ‘fake‐fur’ actually containing the real thing. This is a serious issue for people who object to the use of animals in food and fashion and a clear example of fraud. Hair analysis can rapidly distinguish between a natural hair and a synthetic ‘faux fur’ fibre (the synthetic material would have uniform measurements and lack a scale pattern or a medulla). Although natural fur is considered a luxury item, mass fur farming in Asia has driven prices down to the point at which it is sometimes cheaper for manufacturers to use real fur rather than artificial fibres.
10.2.1.3 Scats as Forensic Indicators
Many mammals produce characteristically formed faeces – called scats (Chame 2003). These indicate the presence of an animal in a locality. Ecologists therefore use scat monitoring to estimate the abundance and movements of elusive animals (e.g. otters). In a forensic context, scats indicate the presence of an animal such as a scavenger, a pet held for ransom (increasingly common), badger baiting or live animal trafficking. The scats also provide evidence of the animal's health and the food it consumed. Faeces can also yield DNA to confirm both species and individual identity.
The UK has a low mammalian diversity (101 species) and therefore many scats can be identified with reasonable confidence. However, the size ranges of many mammals overlaps and where they share a similar diet it can make differentiation difficult – especially as scat form is affected by the animal's health and exposure to the weather. It has been suggested that the bone content and composition within scats provides an indication of the animal that produced them. This could be useful where there are concerns about which animal was responsible for the death of a domestic animal. This frequently happens when wild carnivores are reintroduced to an area or there are strict laws governing the shooting of wild animals. For example, in parts of North America, concerns often arise about whether a sheep or other domestic animal was killed by feral dogs or a puma.
10.2.1.4 Red Blood Cell Morphology as a Forensic Indicator
Mature mammalian red blood cells are spherical and lack a nucleus. By contrast, the red blood cells of birds, reptiles and amphibians are usually larger, oval, and contain a nucleus (Figure 10.5a–c). This provides a quick check in cases in which a person claims that bloodstains result from a legal activity. For example, a man suspected of badger baiting claims that bloodstains on their clothing result from gutting fish after an angling trip. Mammalian red blood cells have a biconcave profile and when viewed with a light microscope the central depressed region appears paler than the surrounding area: this frequently tricks the unwary into thinking that this is a nucleus.
Figure 10.5 Red blood cell microstructure. (a) Mammalian red blood cells (human), (b) avian red blood cells (chicken), (c) amphibian red blood cells (toad).
The shape of mammalian red blood cells is similar and their diameter does not necessarily equate to the size of the animal. For example, human red blood cells are about 7.9 μm in diameter, whilst those of the horse are only 5.5 μm. There are slight differences in the structure of haemoglobin between species that can be demonstrated by high‐performance liquid chromatography (HPLC) (Gray et al. 2015). This could therefore act as a means of species identification, but it is not known how taphonomic processes affect the reliability of this analysis. At present, DNA analysis is the best means of confirming species identity from bloodstains.
10.2.1.5 Identification of Birds from their Morphology
It is often stated that there are 9000–10 000 bird species, but the true figure may be closer to 18 000. A skilled ornithologist can identify the adults of many birds based on their gross morphology. However, if the bird is a juvenile or skeletonised, then it may not be possible to identify it beyond the level of family. Once a bird is processed for food, then it is impossible to identify its provenance based on morphology.
Bird identification is important in a variety of forensic contexts. For example, wild finches and other songbirds are sometimes illegally trapped for sale as caged pet birds, both within the UK and in the Mediterranean regions. Although there is a legal trade in captive bred finches, those that are caught in the wild are thought to have brighter plumage and therefore command a higher price and will sell for up to £100 each. Proving the provenance of these birds depends on correct identification, documentation and, sometimes, DNA analysis. Farmers and gamekeepers sometimes kill eagles and other predatory birds and mammals, because they believe that they kill lambs and game birds. This is usually done by shooting or providing poisoned baits. Therefore, the finding of a dead eagle, for example, especially one in outwardly good condition, might be considered suspicious. It is the responsibility of a vet to carry out a careful autopsy and submit tissues for toxicological analysis.
10.2.1.6 Feathers as Forensic Indicators
Like hairs, feathers are formed mainly from keratin. Feathers are a characteristic feature of all birds and excellent forensic indicators. The size, shape, and coloration of feathers are often characteristic of a species and sometimes a bird can be identified from just a single feather. Feathers are also a source of DNA and their stable isotope content can indicate whether a bird is wild or captive bred and whether it is a resident or a passing migrant. Feathers are classified into three basic types (Table 10.2).
Table 10.2 The three basic types of bird feather.
| Feather type | Alternative name (singular) | Features |
| Contour | Plumae (pluma) | Robust feathers that provide the contour of the body. Subgroups include the wing feathers (remiges) and the tail feathers (retrices) |
| Down | Plumulae (plumula) | Soft feathers that provide insulation. Barbules lack hooks so barbs do not interlock |
| Hair | Pin feathers/Filoplumes | Function uncertain but probably sensory. Lack barbs or just a few of them at the tip of the rachis |
A contour feather consists of two regions: the calamus and the rachis. The calamus region is bare, partially embedded in the skin, and partially exposed. Numerous interlocking barbs arise either side along the length of the rachis region and form the two ‘vanes’ of a feather. The barbs consist of a central ‘ramus’, to either side of which are numerous ‘barbules’. In the region closest to the skin surface, the barbs are soft and fluffy (downy) and those furthest away are stiff (pennaceous) and responsible for giving a feather its characteristic shape, texture and colour. In the pennaceous region, the barbules have hooklets so that each barbule can interlock with the one immediately above it. The shape of these barbules varies considerably, both between feathers and between individuals.
Once a bird has decayed, been processed for food, or if it hits a vehicle at high speed (e.g. an aircraft suffers ‘bird strike’), then the only evidence might be a few feathers. The size, shape, and coloration of contour feathers will indicate not only what region of the body it came from but also the likely species. For example, in tail feathers, the vanes on either side of the central shaft are equal in width, whilst in primary flight feathers the leading vane is narrower than trailing vane. In waterfowl such as swans, ducks, and geese, the primary flight feathers have a tegmen – this is shiny patch parallel to the shaft on the underside of the vanes. The tegmen is formed from specialised barbs that tightly overlap one another and provide structural strength that prevents the vane from splitting during flight.
The fine structure of feathers also helps identify the family or species of bird (Figure 10.6). To do this, pluck a few downy barbs from the base of a contour feather, place them on a microscope slide and cover with a few drops of water. Allow the barbs to spread out and then place a cover slip on top of the preparation and observe using a microscope at ×200–×400.
Figure 10.6 Barbules of (a) chicken (Gallus gallus domesticus), (b) moorhen (Gallinula chloropus), (c) song thrush (Turdus philomelos).
10.2.1.7 Bird Eggs as Forensic Indicators
All birds reproduce by laying eggs and the size, shape, and coloration of these is often characteristic of a species. As one would expect, larger birds lay larger eggs, but smaller birds lay the largest eggs as a proportion of their body size. For example, ostriches (Struthio camelus) lay eggs that are 2% of their body weight, but those of wrens (Troglodytes troglodytes) are 13% of their body weight. The coloration and markings on eggs can vary, even within a single clutch and this variation encourages egg collectors to take all the eggs in a nest rather than a single specimen. All species of wild birds, as well as their nests and eggs, are protected under British Law, although allowances are made to control pest species, such as feral pigeons, and for the shooting of game birds.
Egg collecting was once a common hobby, especially among schoolboys. However, in the UK, it became illegal to collect the eggs of wild birds in 1954, and since 1982 it has been an offence to own the eggs of wild birds. Despite this, egg collecting remains a hobby of some people, and they can have a serious impact on the populations of the rare species, such as many of the birds of prey. Perhaps surprisingly, there does not appear to be a big international trade in wild bird eggs. Consequently, egg collectors are usually only sourcing eggs for their own satisfaction rather than profit. Proving the provenance of wild bird eggs is less of a problem in ensuring a conviction, because possession alone is a crime – although it always helps to know when and where the eggs were obtained.
It was once thought that the shape of bird eggs is related to their nesting habits (e.g. birds that nest on cliff edges have elliptical eggs to prevent them rolling out the nest). However, biophysical analysis by Stoddard et al. (2017) indicates that shape is influenced largely by a bird's flight behaviour, because this influences body shape and this in turn influences the amount of constriction an egg experiences as it passes down the oviduct. Therefore, birds that are streamlined and adapted for fast powerful flight (e.g. the swift, Apus apus) have extremely elliptical eggs.
The identification of eggs is important for combatting illegal egg collecting and the trade in protected species, such as raptors and parrots (it is easier to transport fertile eggs than live adult birds). Although bird eggs, especially those with characteristic markings, can sometimes be identified to species level, many species are difficult to identify. If the eggs hatch, then the young can be reared to confirm species identity, but if they do not hatch, then DNA analysis can be used. Stable isotope analysis can identify whether the eggs came from wild or captive reared birds and, potentially, the region of the country the parent birds were living.
Reptile eggs are always white or cream and therefore any egg that is coloured can only be from a bird. Most reptile eggs lack a mineralised shell and therefore after they are blown they feel soft and rubbery – by contrast, bird eggshells are calcified and therefore hard and brittle. Some reptiles produce eggs with hard shells, but a key morphological difference is that all reptile eggs lack chalazae (twisters). Birds incubate their eggs and turn them periodically and the chalazae ensure that when the egg is turned the embryo remains on top and closest to the warmth of the parent bird. By contrast, reptiles do not move their eggs after laying them and therefore there is no need for the position of the developing embryo to change.
10.2.1.8 Identification of Fish from their Morphology
As of 2015, 33 100 species of fish had been described, but the actual number of species is probably much higher, because large areas of the sea are poorly known. The identification of fish is important to combat the illegal trade in protected species (for food and as pets) and to prevent fraud in which species are intentionally mislabelled (e.g. a common species is marketed as being a premium species or farmed fish is sold as ‘wild caught’. There is an enormous amount of fish mislabelling and this is not helped by the fact that the common names for fish vary between locations. For example, six different species of fish are known as ‘cod’ in the USA and only one of these is the same as the one (Gadus morhua) in Europe.
Adult fish are sometimes identifiable from their gross morphology, but some groups of forensic importance are notoriously difficult to identify in this way, such as the freshwater eels (Anguilla spp). Juvenile fish and those that are processed for food can be impossible to identify based on morphology. Therefore, DNA barcoding is being used increasingly for the identification of fish.
10.2.2 Molecular Identification of Vertebrate Species
Molecular techniques are extremely useful for species identification of animal tissue and fluid samples. For example, when bloodstains are found at a crime scene, food products are mislabelled or the body parts of protected species of wild animals are illegally sold and trafficked. The Consortium for the Barcode of Life (www.barcodeoflife.org) aims to identify sequence data that can be used to provide a barcode for all organisms. For many vertebrates, the mitochondrial gene for cytochrome c oxidase I (COI), is effective, but other mitochondrial gene sequences, such as those for cytochrome b,12S rRNA, 16S rRNA, and the hyper‐variable displacement loop (D‐Loop), are also used. For birds, the genes coding for cytochrome b and 12S rRNA are reportedly better for species identification than COI (Coghlan et al. 2012b).
12S rRNA sequencing has been used to identify meat from endangered species being sold on local markets in China (Wang L.P. et al. 2015). For a number of species, genetic markers can distinguish between populations of the same species (Ogden and Linacre 2015). These can be particularly useful in wildlife forensics when attempting to distinguish between wild and captive bred animals and identify the provenance of ivory or other illegally traded wildlife products. For example, Mondol et al. (2015) identified locality‐specific allele frequencies for the leopard (Panthera pardus fusca) in India. Then, by extracting DNA from confiscated leopard pelts, they identified where the poaching hotspots were occurring and distinguished between small‐ and large‐scale poaching activity. When only a small number of pelts were seized, these did not necessarily originate from the local leopard population. Indeed, many of these pelts originated from central India, thereby indicating that a trading network existed within the country. By contrast, when large numbers of pelts were seized, these were obtained from multiple sites from around India. This indicates organised criminal activity capable of coordinating the movement of these pelts.
Researchers can compare sequence data from their samples with those stored on GenBank and BOLD, and the degree of similarity is used to identify the unknown sample. Mitochondrial gene sequences are particularly appropriate to this task, since they tend to show greater differences between closely related species than do nuclear gene sequences, whilst exhibiting relatively low levels of intraspecific variation. This is owing to mitochondrial DNA evolving faster than nuclear DNA and not undergoing recombination. In addition, because most animal cells contain many mitochondria, a single cell will yield numerous mitochondrial genomes. This, together with the possibility of identifying species from short sequence lengths (mini barcodes), makes mitochondrial gene sequencing particularly suitable for forensic analysis of samples, in which the DNA is degraded through processing (e.g. in foodstuffs) or the animal decaying.
Many of the attempts at identifying animal species in food products have focused on sequencing mitochondrial cytochrome b gene (Teletchea et al. 2005). This has proved particularly effective for the identification of fish and fish products, especially when there is a need to distinguish between closely related species of fish. For example, the fishing of Bluefin tuna (Thunnus thynnus) is carefully regulated (particularly the Atlantic populations, which are at critically low levels), but that of other tuna species is not. Distinguishing between species is difficult because many morphological features are removed intentionally after the fish are caught or during processing (Lin et al. 2005). Mitochondrial DNA is also useful for distinguishing between shark species.
There is a big market for shark fins and jaws, particularly in China and Asia. Although many shark species have protected status, illegal fishing has led to catastrophic declines in their populations. For example, populations of the scalloped hammerhead shark (Sphyma lewini), which was once considered at low risk owing to their wide distribution, have declined by as much as 98% in some regions. The processing of sharks usually takes place at sea – sometimes the fins are cut off and the animal is pushed back into the water to die. Consequently, there are few morphological features available to determine whether the fins came from protected species. Protection agencies therefore use DNA techniques, especially mitochondrial COI and mitochondrial cytochrome b sequences to identify illegally caught shark products. Similarly, Marko et al. (2004) found that 77% of the fish sold as red snapper were actually other species – such widespread misrepresentation has serious consequences for the management and conservation of fish stocks. The need to distinguish between fish species also arises to prevent fraud; for example, when cheap farmed fish is wrongly marketed as more expensive wild‐caught fish of the same or a different species (Kyle and Wilson 2007).
Traditional Chinese Medicines often contain complex mixtures of animal and plant products and identifying their composition can present difficulties. The same is true in cases of suspected adulteration, in which processed foods might contain a small proportion (or none) of the stated meat and a mixture derived from other animals. To identify all the species contributing to the medicine or food, it is necessary to sequence several barcode templates in parallel. An alternative approach, especially if the likely composition of the mixture is uncertain, is to use Next Generation Sequencing (NGS) technology. Whilst NGS is not yet widely employed for the identification of vertebrates or for wildlife forensics, it is likely to become more popular in the near future. Coghlan et al. (2012a) utilised NGS to analyse a range of Traditional Chinese medicines and demonstrated the presence of not only protected species such as the Saiga antelope (Saiga tatarica) but also potentially toxic plants. Staats et al. (2016) provide an excellent review of the use of barcoding to identify vertebrates.
Sequencing of the mitochondrial cytochrome b gene has proved useful in the detection of animal parts in Traditional Chinese Medicines. Although the use of rhinoceros horn in traditional medicines is now illegal in China, the practice continues. Whole rhinoceros horns can be easily identified from their morphology, but it is more difficult once they are ground to a powder or made into sculptures. By amplifying and then sequencing a partial (402 base pair) fragment of the cytochrome b gene, it is possible to distinguish between species of rhinoceros and to detect the presence of rhinoceros DNA, even when powdered rhino horn is diluted with cattle horn (Hsieh et al. 2003).
Pyrosequencing works by identifying one base at a time along the length of a strand of DNA, through the release of light whenever a ‘match’ is found. It is particularly effective for distinguishing between bacteria in forensic, medical, and ecological studies (e.g. Javan et al. 2016). Karlsson and Holmlund (2007) describe how it can identify human DNA and distinguish it from that of other mammals. They amplified fragments of 12S rRNA and 16S rRNA by Polymerase Chain Reaction (PCR), and then sequenced these using the pyrosequencing cascade system. Obviously, as a means of discriminating between species, this technique is most reliable when there are many nucleotide differences between their DNA templates. They found a minimum of nine nucleotide differences between the sequences for humans and a variety of European mammals, indicating that this is a good way of distinguishing human from non‐human blood or tissue samples. Pyrosequencing can identify many domestic and wild mammals and is a rapid means of identifying fish species (De Battisti et al. 2013). Also in its favour, pyrosequencing is fast, accurate, and easily automated, so it can be used for large‐scale surveys. In addition, it is quantitative, since the amount of light formed can be related to the amount of nucleotide base binding to the DNA template.
10.2.2.1 Limitations on the Use of DNA for Identification of Vertebrates
The usefulness of DNA‐based species identification as a forensic tool is increasing all the time, although there remain concerns about the need for standardised protocols for DNA extraction and analysis of the gene sequences and quality control. For some species, there is a need for more sequences from voucher specimens to indicate the degree of intraspecific variability (number of haplotypes). For example, if the data stored on GenBank or BOLD contains errors through incorrect identification of the animal from which the DNA originated, contamination with human DNA or that of other animals, or the way the sample was processed, it will lead to misidentification.
Similarly, if sequence data for a given species is available for only a single haplotype, it might lead to other haplotypes of the same species being considered to belong to a different species. There is also concern over the extent to which fragments of mitochondrial DNA are translocated into nuclear DNA. These fragments, known as Numts, can become sequenced alongside or instead of the target mitochondrial DNA and thereby cause problems in interpreting the results. Numts have been identified in over 40 species of mammal. They pose a particular problem in cats, in which almost half the mitochondrial genome has transposed into the nuclear genome. Therefore, one must ensure that the intended mitochondrial DNA gene sequence is genuinely the one that is amplified and sequenced. Problems of identification also arise when attempting to distinguish between recently diverged species or hybrids of closely related species.
10.2.2.2 Molecular Identification of Individual Animals
The need to identify a specific individual animal usually arises when it is necessary to link an animal to a crime scene or to a suspect. Early attempts at this tended to have limited discriminatory capacity, although where obvious differences in sequence data were found, they were sufficient to indicate the absence of a ‘match’. For example, Schneider et al. (1999) describe a case in which a dog, which was believed responsible for causing a traffic accident, was exonerated following a comparison its mitochondrial D‐loop region sequence with that obtained from hair fragments found on the damaged car. This technique was only suitable for excluding suspects rather than identifying culprits, owing to limited polymorphism of the canine mitochondrial D‐loop region.
Currently, Short Tandem Repeat (STR) arrays are available for several domestic animal species. These are used in the same way as those for human identification. For example, dogs are identified with the DogFiler multiplex assay that uses 16 STR loci. Blackie et al. (2015) used this kit to develop profiles from single guard hairs that were shed naturally. This means that the dog hairs are now even more valuable as trace evidence. Dogs are common pet animals and many of us unintentionally (and often unwillingly) carry with us evidence of that association. Horses can be identified using a combination of 12 STR loci and Tobe et al. (2007) describe how these were used to confirm that a urine sample that tested positive for an illegal drug came from a particular racehorse. Horseracing is notorious for alleged intentional doping and rivals making false allegations. Consequently, when a match was found between all the STR loci isolated from the urine sample and those of the hair samples taken from the horse, this could be taken as good evidence that the sample did indeed come from that horse.
Dogs can be DNA tested by taking a saliva sample in a similar way to humans. In the case of dog bites, DNA recovery is more effective from severe bite wounds than those that are relatively light (Eichmann et al. 2004). At first sight, this appears odd, because severe wounds bleed heavily and therefore the swabs would be badly contaminated with human DNA. However, severe wounds result from extremely forceful and often prolonged contact between the dog and its victim: consequently, the dog's saliva is transmitted liberally into the wound and smeared onto the surrounding skin. By contrast, light wounds usually result from a quick snap or nip, resulting in relatively little saliva being transmitted and, crucially, these wounds are more likely to be washed before medical attention is sought, thereby further reducing the amount of canine DNA present. Analysis of DNA from dogs and other domestic animals is not only of value when the animal itself is the suspect or victim of a crime, but may also be used as a means of providing a link between people or between people and a location. Coyle (2007) provides a review of canine and feline DNA analysis in a forensic context.
10.2.3 Chemical Identification of Vertebrate Species
A variety of techniques is available to identify animal species based on their chemical composition. These methods are mostly appropriate for specific scenarios, rather than ones that would be used by taxonomists.
X‐ray diffraction can be used to distinguish rhino horn from that of other species and ivory from antlers (Singh et al. 2003). X‐ray diffraction is based upon measuring the scattering (diffraction) of an X‐ray beam after it hits a sample. It is a non‐destructive technique and reveals not only the crystalline structure of the sample but also details of its chemical composition and physical properties. The technique requires only small amounts of material and the sample is analysed as either a single crystal or a powder. In a forensic context, the samples are usually in the form of powders. The amount of sample required depends on the machine, the nature of the sample and the type of information required – it may be as much as a few milligrams or less than 1 μg. If the sample contains many different components and it is necessary to identify them individually, more material is required. It is commonly used for the analysis of paints, soils, drugs, bullets and gunshot residues, metals, powders that are alleged to contain anthrax spores, and a host of other situations (Rendle 2003). The results are usually presented as a trace of peaks and troughs, which is called a diffractogram. The diffractogram represents the photon counts of X‐ray radiation as a function of the angle of diffraction. Diffractograms from, say, known rhino horn can be compared with those of an unknown to determine their similarity. Alternatively, individual components from within a mixture can be identified from the similarity of parts of the diffractogram to those of known standards. The downside of the technique is that the equipment is expensive and requires trained technical support.
Infrared spectroscopy is a commonly used laboratory technique for determining the composition of materials. In forensic science, it is often used in trace evidence analysis. For example, when a woman is discovered burnt to death in a kitchen, infrared spectroscopy can be used to determine the presence of petrol or other accelerants on clothing and thereby distinguish a ‘kitchen accident’ from a homicide. The analysis is based on directing a beam of infrared wavelength light onto an object and then measuring the spectrum of light that is either absorbed or transmitted. There is a variety of infrared spectroscopic techniques, but Fourier transform infrared (FT‐IR) spectroscopy is often used in the analysis of biological samples such as hair and has the advantage of being non‐destructive. For example, in parts of Africa, bracelets, necklaces, and flywhisks are sold that ostensibly come from the tail hairs of elephants or giraffes, but could also be made from synthetic material or hairs from domestic animals. African elephants are listed in Appendix I under CITES legislation, but giraffes are listed in Appendix II. Therefore, it would be illegal to import any item made from elephant hair into a country that is a CITES partner, but if they were made giraffe hair or from other sources, they could be imported without a permit (some partner countries take a stricter approach to the import of Appendix II species). It is difficult to distinguish the tail hairs of elephants and giraffes on their macroscopic appearance, although differences in the distribution of pigment are apparent when the hairs are viewed with a light microscope. Although all mammalian hairs are composed of keratin, there are differences between species in its chemical composition and this is detectable using FTIR spectroscopy (Espinoza et al. 2008).
Raman spectroscopy is now a common analytical tool and has many applications in forensic science. It works on the principal of shining a monochromatic light from a laser onto an object and then measuring the spectrum of light that is emitted. The spectrum is then compared to those stored in a database to determine the nature of the material being tested. The development of hand‐held devices means that the technique can be used in field situations.
Raman spectroscopy can be used to locate bloodstains and distinguish between bloods from different species of mammal (McLaughlin et al. 2014). The use of Raman spectroscopy for this application is still in the developmental stages, but it may be useful for the identification of blood from other species of animal too. The technique also shows promise for the identification of bones, horns, antlers, and tortoise shells (Turner‐Walker and Xu, 2014).
Stable isotope ratios cannot identify an organism, but they are useful for determining provenance and diet. Isotope ratio analysis relies on the fact that the chemical characteristics of the soil on which an animal lives are reflected in the levels of chemicals and their isotopes present in their hair, bones, and teeth. In this way, it has proved possible to identify the geographical origin of ivory and bone (Stelling and van der Peijl 2003). However, to be fully effective, this requires a comprehensive database of soil chemistry characteristics from those parts of the world where the animal is thought to have originated.
Stable isotope ratios can indicate feeding relationships, because predators tend to contain higher levels of 13C and 15N than their prey. The technique is particularly effective in aquatic organisms. Farmed fish are often fed pellets containing high levels of protein and fat derived from other fish, whilst their wild brethren have a more diverse and less concentrated diet. Consequently, farmed fish have high levels of 13C and 15N and this distinguishes them from ‘wild’ fish.
Sometimes an animal's chemical composition is affected by its diet and this can be used to identify the circumstances under which it was reared. For example, the fatty acid composition and mineral composition of fish are both affected by their diet and this can be used to distinguish between those that are farmed and those caught in the wild (Alasalvar et al. 2002). This is important because wild caught fish are commonly believed to be more nutritious and have a better flavour. Therefore, wild fish often sell for up to double the price of farmed fish. Between October 2005 and August 2006, the UK Food Standards Agency examined the fatty acid profile and isotopic ratios of 13C : 12C, 15N : 14N, and 18O : 16O in a range of fish purchased from supermarkets and shops around the country. They found that 10% of sea bass, 11% of sea bream and 15% of salmon that were marketed as ‘wild’ had definitely originated from a fish farm. Although not necessarily representative of the whole retail industry, the results indicate a potentially widespread problem with fish labelling. Similar worries concern the labelling of free‐range and organically grown farm animals and crops.
10.3 Vertebrate Scavenging of Human Corpses
Many vertebrates exploit corpses as a source of food and a human body will be consumed in a similar manner to that of any other medium‐sized mammal. In northern European terrestrial ecosystems, this usually means dogs and other canids, rats, pigs and birds, such as crows, ravens, buzzards, and jackdaws, whilst in aquatic ecosystems various fish and seagulls are responsible. However, even vertebrates that are normally considered herbivores, such as squirrels (red and grey), sheep and cows will gnaw on bones, especially if they are living in a nutritive poor environment. For example, in USA, white tailed deer (Odocoileus virginianus) have been observed chewing on the ribs of a human skeleton (Meckel et al. 2017). The deer will contribute to the disarticulation of the skeleton and cause characteristic forking of the bone at the chewed end. In common with other ungulates that chew on bones, the deer only gnaw on dry bones.
Dogs (Canis familiaris) are well known for their scavenging activities. They will spread body parts over several metres and bury bones and limbs, thereby making it impossible to recover a whole skeleton. Although dogs have a partiality for bones, they tend to scavenge corpses that are fresh or only just starting to decay (Haglund 1997). The ability of dogs to locate human remains even after burial, can result in a body being unearthed, despite the best efforts of a murderer to conceal it, and this is exploited in the training of ‘cadaver dogs’ by police agencies. Scavenging invariably results in serious damage to the victim's body and may lead an investigator to assume initially that a person who died of natural causes or suicide was the victim of a brutal killing. Feeding often begins on the head and neck and the loss of tissue along with the consumption of the thyroid cartilage and hyoid bone can make the diagnosis of strangulation, among other causes of death, impossible. The arms then tend to be pulled off, followed by the legs – this order probably reflects the relative ease with which they can be grasped and disarticulated. Clothing is seldom an impediment to the body's consumption and disarticulation. Indeed, the scattering of the clothes and removal of the genitals/genital regions of both men and women can raise the suspicion of sexual assault (e.g. Romain et al. 2002). The damage dogs, etc. inflict therefore needs to be distinguished from that caused at the time of death or by a murderer cutting up the body of their victim.
Bite wounds inflicted after death – like all such wounds – do not usually bleed to any great extent. Consequently, the surrounding bloodstains would be distinct from the spatter pattern emanating from a living person. Bite wounds sometimes indicate characteristic tooth marks, whilst claw scratches can indicate the paw size. These may enable not only the species responsible to be identified but also the individual animal. The latter is especially the case where the person dies indoors or in an enclosed space, in which the suspect animal(s) are also confined. In addition to the tooth marks, animals may also leave hairs from their muzzle whilst feeding, the individual characteristics of which, along with extracted DNA, may be used for identification. The stomach contents of pets and domestic animals may also be examined to determine whether they fed on a body, but it is seldom possible to catch wild or feral animals for analysis.
Dogs and other carnivores produce four types of damage to bone: punctures, pits, scoring and furrows (Haglund 1997). Puncture marks are usually found in thin bone such as the scapula and are caused by the canine teeth and/or carnassial teeth penetrating through the full thickness of the bone. The size, shape, and distribution of the puncture marks can give an indication of the size of animal that inflicted them. Pits are indentations that are inflicted by any of the teeth when grasping onto bone, whilst score marks result when the teeth are dragged along the surface of the bone. Furrows are deep channel‐like grooves found along the length of the long bones such as the femur and are caused by the molars and premolars. When a dog spends a long time chewing on a bone, it turns it over and over, resulting in a mass of grooves and pits from which it is difficult to discern individual tooth marks.
Canids and felids always chew with one side of their mouth, because their large canines make side‐to‐side chewing motions impossible. The different types of tooth marks can usually be distinguished from the cutting or sawing damage caused by human tools, and they do not induce bevelling or concentric or radiating fractures such as those caused by gunshot wounds or trauma induced from a blunt or sharp implement. Archaeologists have done a lot of work on distinguishing between the damage caused to bones by different animals, as opposed to humans, and the effect of different types of cooking (Brain 1983). On soft tissues, tearing and puncture marks can sometimes be matched with the tooth structure, dental formula, or claws of the animal responsible, whilst the presence of animal hairs in the wound and/or faeces in the vicinity provides further corroborating evidence. Domestic cats (Felis catus) do not cause as much physical destruction as dogs, and their bite marks tend to be more dispersed and the tooth marks more defined (Moran and O'Connor 1992).
Dogs and other canids are not dainty eaters and they often swallow fragments of clothing from a corpse along with its flesh. Consequently, clothing fibres may be found in the animal's faeces. When hyenas and leopards swallow fingers and toes, these pass through their digestive system and are excreted in their faeces (Pickering 2001). Bone fragments and even whole teeth are often found in the faeces of dogs, foxes and other carnivores. Rings and other jewellery, especially gold, will pass through a digestive system largely unharmed, but usually shows signs of acid etching. Therefore, an analysis of nearby faecal deposits and any dens, sets, or burrows may yield missing bones and jewellery. The skeletons of young children do not survive scavenging attack as well as those of adults. Not only are their bones smaller and weaker, but also the epiphyseal plate, a band of proliferating and developing cartilaginous cells in the epiphysis (head) of the long bones, is thicker in children and is easily chewed away by a carnivore. The bone shafts are then swallowed and are broken down more readily in the stomach because of their lower calcium content. Similarly, the sutures between the skull bones of infants and young children are movable, thereby enabling the skull to be broken more easily than that of an adult.
An assessment of a dog's mental state and relationship to humans is required when accused of scavenging or attacking a human or another animal. This is obtained from witness statements (where possible) of the dog's past behaviour, it's behaviour at the time it was impounded, and an assessment made by an experienced animal handler or behaviourist over the following days. In previously well fed and otherwise normally behaved pet dogs and cats, post‐mortem scavenging behaviour is commonly thought not to take place until long after the death of their owner and the onset of starvation through being confined in a room or building with no alternative food supply. However, there is a great deal of variation between cases, and it is possible for the body to be substantially consumed within a short period of time (Steadman and Worne 2007). Rothschild and Schneider (1997) describe a case in which scavenging by an Alsatian dog took place within 45 minutes of the owner committing suicide by shooting himself in the mouth (hence a large wound was already present on the body). They discuss several possible explanations for the early onset of scavenging, including aggressive behaviour caused by being confined and the dog, being a pack animal, attacking its owner at a time of weakness in an attempt to gain a social domination. However, they considered the most likely explanation was that initially the dog attempted to help its unconscious (or recently deceased) owner by nuzzling and licking him. However, when these attempts failed, it panicked, attacked, and mutilated him.
When rodents gnaw on bones or other objects, they leave paired parallel grooves with intermediate ‘groins’ – the width of the grooves indicates the size of the incisors and hence the size and probable identity of the rodent species. Many rodents will feed on corpses, and porcupines are notorious for collecting all sorts of objects in their burrows, ranging from bones to tin cans. In the UK, field mice exhibit a similar acquisitive nature. Grey squirrels (Sciurus carolinensis) prefer dry bones (Klippel and Synstelien 2007) and there are no reports of them feeding on fresh bodies (however, when the opportunity presents, they will kill small mammals and young birds). Rats will remove flesh from living bodies and historical accounts of soldiers and prisoners living in unhygienic circumstances often mention rats nibbling at fingers and toes. Rats (mainly Rattus norvegicus in the UK) also favour soft, moist areas such as the eyelids, nose, and lips.
Consequently, rodent bite marks are inflicted both before and after death upon a person who dies of wounds, disease, or intoxication over a period of days. They are commonly found on the bodies of homeless people or those living in squalid conditions. Large numbers of rats can overwhelm and kill a person who is already comatose or too weak to defend himself, but documented cases of such instances are rare. Unhygienic circumstances are not always a factor in rodent scavenging, because many people keep rats and other rodents as pets. For example, Ropohl et al. (1995) describe post‐mortem wounds caused by a free‐range golden hamster (Mesocritecus auratus) that were so extensive that it was initially believed to be the work of a murderer attempting to scalp his victim. The hamster was identified as the culprit, because of its typical ‘rodent signature’ – rodents often leave characteristic faecal pellets (their shape and size varies between species) whilst feeding and their paired chisel‐shaped incisors cause crater‐like lesions with notched edges in soft tissue (Tsokos et al. 1999). The hamster further incriminated itself by taking fragments of skin and tissue back to its nest – another typical rodent trait. Bite marks do not always cause tissue loss and by stretching the skin, it is sometimes possible to see marks caused by the paired incisors.
In mediaeval times, pigs (Sus scrofa) were allowed to roam freely and there are reports of them biting and even killing and eating babies. Nowadays, this is no longer a problem in northern Europe, although the wild pigs and boar would probably be happy to exploit any dead bodies left in their woods. During experiments with domestic pigs that were fed fresh uncooked bones of sheep, cattle, and pigs, Greenfield (1988) found that sows tend to briefly chew on the first bone they encounter before dropping it and moving on to another and repeating the process. After a short period, the pigs concentrate on the smaller bones, especially the vertebrae, which can be picked up and carried around, and these are completely consumed. Large bones such as the femur are damaged, especially at the ends, but not totally destroyed. Crime writers sometimes suggest that a good way to dispose of a dead body is to feed it to pigs. However, this requires the cooperation of the pig farmer, because a whole body will not be entirely consumed overnight and it is doubtful that the pigs would destroy all the bones.
Many birds feed on corpses or remove hair that is sloughing from its head to line their nests. Carrion crows (Corvus corone) and magpies (Pica pica) usually begin feeding on the eyes of corpses and the tongue if it is extended (Figure 10.7). They may remove sufficient tissue to make the cause of death difficult to establish (Asamura et al. 2003). As sheep farmers will testify, birds do not wait for an incapacitated animal to die and any creature too weak to defend itself may be attacked. Similarly, gulls will attack people swimming in the water after abandoning ship and there are instances of people drowning in their attempts to avoid the birds. Penetrating wounds to the head and a lack of eyes may therefore result from bird attacks rather than murder and these wounds may be caused both before and after death. Birds tend to produce stab‐like wounds, the size and depth of which varies with the size of the bird's beak. Some birds, such as buzzards (Buteo buteo), employ a stab and tear technique when removing flesh. Birds contribute to the dispersal of remains by removing scraps of tissue and body parts. For example, fingers are pulled off and consumed elsewhere at leisure or taken to a nest site to be fed to chicks. Unless birds are seen feeding on a body and/or they leave their faeces, it may be difficult to implicate them with wounds. On land, a lack of bleeding indicates that wounds were inflicted after death, but bleeding is extensive if the body is floating in water.
Figure 10.7 (a) Carrion crow (Corvus corone); (b) eyes pecked out of a recently dead sheep by birds. Similar post‐mortem wounds occur in human bodies.
Many species of fish, both freshwater and marine, will feed upon dead animals and the consequences depend upon the species involved, their abundance and the duration of exposure. Like rats and mice, small fish tend to start feeding on the fingers and toes, earlobes, lips, and nose, and this causes numerous small crater‐like wounds. Prolonged feeding can result in the loss of substantial areas of tissue. Large fish cause wounds that are more serious and sharks, such as the Tiger Shark (Galeocerdo cuvier) and the Great White Shark (Carcharodon carcharias), will bite off and swallow limbs whole. Cookie‐cutter sharks, Isistius spp., as their name suggests, produce unusual elliptical‐shaped wounds (Hayashi et al. 2015). Cookie‐cutter sharks could be considered as ectoparasites rather than predators, because they use their oddly‐shaped mouthparts to scoop out lumps of flesh from their prey rather than kill it. Stock et al. (2017) provide a detailed account of the sorts of damage caused by sharks.
10.4 Vertebrates Causing Death and Injury
Domestic and wild animals are seldom a cause of human deaths in northern Europe but when fatal attacks do occur, they generate enormous publicity and fear. By contrast, dog bites are common and may result in serious injury – and consequent litigation. In England, 6740 people attended hospital for treatment for dog bites between January 2013 and January 2014. This represented a continued increase on previous years and the figures were three times higher in the most deprived areas compared to the least deprived. Wounds are usually inflicted to the extremities, especially when the attack comes from stray or feral dogs, whilst pet dogs are more likely to attack the face or neck. The wounds are life threatening if major blood vessels, such as the femoral artery, are damaged. The wounds may also become infected with bacteria transmitted in the dog's saliva and in some countries there is the risk of rabies. In fatal cases, there is serious loss of blood and often damage to the hands and arms where the victim has attempted to ward off the dog(s). Most fatal dog attacks are on young children, the elderly and the infirm.
Domestic cats have finer and sharper teeth than dogs, which enable them to penetrate bone despite their comparatively weaker bite. Cat owners commonly have fine scratch marks on the backs of their hands, because of playing with their pets. Cats seldom attack unless they are cornered and feel threatened, but when they do, cats can cause serious lacerations before they escape as quickly as possible. There are no reports of them causing death by attacking someone, although tripping over a circling cat is a common cause of injury. For example, an elderly person may be found unconscious with a head injury and crime may be suspected until other evidence – such as the position of the injury and pattern of blood spatter – indicate a fall. However, if the person does not recover or cannot remember what happened, this may be difficult to distinguish from a push by an intruder.
In some sections of the community, large aggressive dogs are popular fashion accessories. In 2008, four breeds of dog were banned in the UK: the American pit bull terrier, Japanese Tosa, Dogo Argentino, and Filo Brasileiro. Sometimes aggressive dogs are merely props to a fragile male ego, but they are also used in illegal dog fighting and as a means of intimidation. During the American invasion of Iraq to topple Saddam Hussein (1990–1991), the use of guard dogs to threaten prisoners was notorious. Proof of intimidation is difficult to establish if no physical injuries are caused, although the American prison guards were callous (and stupid) enough to photograph themselves committing the crimes. In addition to using dogs to bite and intimidate victims, some people have trained them to commit sexual acts and there are reports of them being incited to commit rape (Schudel 2001; Vintiner et al. 1992). Consequently, victims of sexual assault may have traces of non‐human spermatozoa and it may require modifications to existing protocols for their detection.
In addition to the risks posed by normal pets and domestic animals, the increasing popularity for keeping exotic animals has resulted in more people encountering large and potentially dangerous creatures. For example, there are currently more tigers in captivity than there are in the wild. Between the years 1998–2001, 27 persons were injured and a further 7 killed by tigers in the USA (Nyhus et al. 2003). Precisely how many tigers are kept in captivity in the USA is unknown and cross‐breeding between tiger sub‐species and lions and tigers is not controlled. Some deaths caused by captive wild animals are the result of people taking inadequate precautions when housing or handling them. These are often animals kept by private individuals. Keeping exotic pets is a difficult, expensive, and time‐consuming occupation. Therefore, they are commonly dumped once the animals grow too large or aggressive. For example, iguanas are popular pets in the UK, where they are usually purchased when they are 10–20 cm long. However, when mature, they measure up to 180 cm, weigh 9 kg, and become aggressive – at which point they cease to be ‘cute’ and are looked on as a burden. The killing or dumping of unwanted exotic pets can lead to criminal charges, although proof of ownership is difficult, especially if the animal was being kept illegally. Zoos have a duty to not only maintain potentially dangerous animals under safe conditions from which they cannot escape, but also enable them to be seen by members of the public whilst simultaneously preventing the naïve, deranged, or suicidal from coming into contact with them. For example, climbing into a lion enclosure is sometimes used as a form of suicide (e.g. Bock et al. 2000).
Although there is always a lot of publicity associated with a shark attack, such incidents are very rare. In 2015, there were 98 unprovoked shark attacks recorded and 6 of these resulted in someone being killed. By comparison, it is often stated that 150 people are killed every year by falling coconuts and hippos are responsible for killing in the region of 2900 people per year. Interestingly, sharks can retain food undigested within their stomach for several weeks. Some sharks will feed on both dead and living organisms and therefore when part of a human body is discovered within a shark (which happens from time to time), it is not always possible to determine when the part was eaten or whether the shark was responsible for the person's death.
10.5 Neglect and Abuse of Vertebrates
Whilst pets and domestic animals sometimes attack and may even kill humans, they are far more frequently the subject of neglect and wilful abuse that result in the animal suffering and/or dying. Wild animals are also frequently killed for no other reason than personal gratification. To mistreat animals in this way has long been recognised as a crime, but identifying such activity has received a higher profile following the realisation that it is often linked to other forms of violent behaviour. For example, children who are cruel to animals are often themselves victims of cruelty (McEwen et al. 2014). Animal cruelty has also been linked to domestic violence as part of controlling behaviour (Newberry 2017). There is an ongoing debate about whether childhood animal cruelty is a predictor of the likelihood of adult violence to humans (Walters 2014).
The diagnosis of animal neglect and abuse is a job for veterinary surgeons based on the clinical symptoms. Where the animal is voluntarily brought to the surgery, they face the dilemma of reporting the owners to the police and thereby risking the animal suddenly ‘disappearing’ before it can be impounded, or they can keep quiet and attempt to treat the animal whilst encouraging the owners to behave more responsibly. The mistreatment and illegal killing of both wild and domestic animals can result in hefty fines and imprisonment. Consequently, the person charged will mount an active defence and escape punishment on a legal technicality if the investigation is not conducted according to recognised procedure and to the same standard as the forensic examination of a human crime victim (Cooper and Cooper 2013).
Humans have always used a wide range of animals for their own sexual pleasure and Ancient Greek literature is full of strange couplings between humans and other animals – often claimed to be gods in disguise, which is a feeble excuse. However, such activities were frowned on by most communities and if discovered could result in judicial proceedings in which both the man (it usually was a man) and the unwilling object of his attentions were condemned to death. Bestialism was a capital offence in the British Isles as late as nineteenth century: John Leedham had the unfortunate distinction of being the last person in Derbyshire to be hanged for a crime other than murder, when he was executed outside the Derby New County Gaol on 12 April 1833 for bestialism. It remains a common and under‐reported problem – probably because of its simultaneously ludicrous and unpleasant nature. In a survey of small animal veterinary practitioners in the UK, Munro and Thrusfield (2001) found that 6% of 448 reported cases of non‐accidental injury were of a sexual nature. In a survey of juvenile sex offenders in America, Schenk et al. (2014) found that 37.5% of offenders admitted to practising bestialism (although it was not the crime they were convicted of). However, polygraph recordings suggested the real figure was 81.3%.
Wild animals do not always kill their prey quickly and cleanly, neither, contrary to popular belief, do they kill only sufficient to assuage their appetite. Consequently, one may find badly wounded wild or domestic animals that at first sight appear to have suffered at the hands of a sadistic individual. For example, in April 2004, numerous dead and dying frogs and toads were found in Aberdeenshire, with their hind legs ripped off and this sparked a police investigation. It was subsequently discovered that the culprits were otters that bit off the hind legs of their victims and then skinned them. In the case of toads, this is to remove their poison glands. In 2017, there were calls from farmers in parts of Germany and elsewhere in Europe for a cull of wolves. This was because wolf numbers were increasing following several years of protection and, in some cases, re‐introduction. The farmers claim that wolves kill more sheep and other farm animals than they consume and they often leave badly injured animals that have to be humanely killed.
10.6 Vertebrates and Drugs
Dogs have a keen sense of smell and they are used by police forces throughout the world to detect hidden drugs and explosives at airports, train stations and ferry terminals. Intriguingly, African Giant Pouched rats, Cricetomys gambiensis, have a similar ability to be trained to identify distinctive smells in return for a reward. For example, they can detect tuberculosis in sputum and explosives in landmines (Polling 2011). There are no obvious reasons why they could not also be trained to detect contraband drugs or other substances of forensic interest. The rats are said to be ‘more mechanical than a dog and they are easier to transfer to different owners’.
In addition to detecting drugs, animals are also used to smuggle them – although the full extent to which this is happening is not known. For example, there are reports from several parts of the world of pigeons delivering drugs, computer data sticks and sim cards to prisoners. The ‘payload’ is inserted into a small ‘backpack’ attached to the pigeon. In September 2003, at Schiphol airport, Holland, two Labrador dogs, in transit from Colombia, had 21 packets of cocaine sown to their stomachs. Suspicions were raised by the dogs' behaviours, one being aggressive whilst the other was weak. Both dogs had scars and X‐rays revealed the containers. One dog survived the removal of the containers, whilst the other had to be put down because the containers had fused to the stomach lining. The authorities arrested two persons when they arrived to pick up the dogs. The presence of scarring and unusual behaviour of any animal transported between countries should therefore arouse suspicions. In a similar case in 2013, dogs were force fed packages of cocaine by traffickers who then shipped them from Mexico to Italy. Because there is no quarantine in Italy, local gang members were able to pick up the dogs on arrival at the airport and then butchered them to retrieve the drugs.
Forty‐eight dogs were killed and the trafficking was discovered through a combination of normal policing and chance events. The drugs were wrapped in Clingfilm and black vinyl tape (some reports said carbon paper) in the belief that this would prevent them being detected by X‐rays. This is highly unlikely to have been successful, so presumably the animals were never checked. Even if X‐raying every animal is not feasible, anyone who handles drugs and then an animal is likely to transfer drug residues to the animal's coat – and these can be detected by routine screening tests at the airports on departure and arrival.
The use of alcohol and drugs is widespread and it is not unusual for domestic animals to become unwilling partners in their consumption. The consequences can be fatal for both man and beast. For example, domestic animals can accidentally ingest alcohol and drugs that are left lying around a property and the surrounding area. In 2017, in the UK, a Staffordshire bull terrier dog went ‘out of control’ and fatally mauled its owner. The man was a cocaine user and when he started to suffer an epileptic fit, his dog attacked him. Subsequently, the dog was shown to contain high levels of cocaine and these were suggested to be the reason it became violent. It was presumed that the dog accidentally consumed drugs that had been left lying around the man's flat. There are reports from Scotland that drug dealers intentionally inject their dogs with heroin to make them more aggressive. It is probable that the practice is much more widespread. Animals are also intentionally given alcohol and drugs ‘for a joke’ or in the misguided view that they will enjoy it. In some states in USA, commercial companies are marketing marijuana for cats and dogs as a ‘treat’ and a home remedy for treating inflammatory conditions and anxiety. There is currently no scientific evidence that cannabis is of any benefit to dogs and cats, the drug is not legalised for the treatment of animals and some reports state that dogs given marijuana become frightened and trembling. The effect of a drug on any animal depends upon the species, the individual, the nature of the drug and the concentration. For example, opioids cause pinpoint pupils in dogs and dilated pupils in cats. Animals develop an addiction to drugs in the same way as humans. Alcohol and opiate overdoses in domestic animals cause vomiting, uncoordinated movement, breathing difficulties and, in severe cases, death. Forensic evidence is provided by toxicological analysis. Intentionally giving drugs or alcohol to an animal counts as animal abuse.
Just as the use of drugs is a problem in human sporting activities, so is the administering of drugs to competition animals. The extent of the problem is uncertain; The University of Ghent, Belgium, runs a doping control laboratory and between 1993 and 2003, they found 1.2–8.4% of horse samples and 3.6–6.6% of human samples tested positive. In the UK, there is routine random drug testing of racehorses at events. In addition, testers are authorised to arrive at stables unannounced to collect their samples. The drugs involved are often those used in the treatment of disease, but are administered solely to improve performance, for example, erythropoietin (EPO) (which increases the red blood cell count), clenbuterol (a bronchodilator) and propantheline bromide (blue magic) (a muscle relaxant that also acts to increase a horse's lung capacity). Therefore, owners of competition horses must be careful about the medication their animals receive and aware of the risks of spiked feed or inadvertent feeding inappropriate food. For example, in the USA, owners of show horses are warned not to allow their children to reward them with drinks of Coke, because it might increase the caffeine levels above allowable levels.
The use of ‘downers’ to reduce the activity of horses is allegedly common practice, although supporting evidence is not readily available. This might be done to make a troublesome horse more placid at the time of sale, to cause it to lose a race, or to make it more manageable in the ring. The organisation ‘Ponies (UK)’ has a programme of random dope testing, following judges and stewards voicing concerns over the placid behaviour of some of the smaller horses ridden by children. Bute (phenylbutazone), a non‐steroidal anti‐inflammatory drug, used in the treatment of strains, sprains, and feverish symptoms is one of the suspects, although non‐specified herbal remedies are also thought to be involved. In 2002, a British trainer was fined £600 by the Jockey's club when one of his horses was found to contain traces of the ‘stopping’ drug acetylpromazine (ACP). Obviously the drug was not in a high enough concentration, because the horse won by 11 lengths.
In 2017, in Jacksonville, Florida USA, there were 18 incidents of greyhounds testing positive for cocaine in four months and later in the year more cases were reported in Northern Ireland. The problem is therefore likely to be widespread. There is no evidence that ‘coked up’ greyhounds run any faster, so it may have been administered in hope rather than with a realistic expectation. Regardless of the effectiveness of dosing a greyhound with cocaine, the practice is illegal and potentially harmful to the dogs. Racing causes the body temperature of a greyhound to rise and cocaine can exacerbate the risk of potentially fatal overheating. There are also reports of racehorses testing positive for cocaine. There are standard procedures for testing for cocaine, but the detection of gonadotropin‐releasing hormone (GnRH) and GnRH analogues presents more difficulties. GnRH stimulates testosterone production and can thereby improve athletic performance. The detection of GnRH is problematic, because it is rapidly cleared from the body after being given as a drug and degrades quickly in urine. GnRH abuse has been an issue in human sports for several years and is now happening in greyhound racing.
10.7 Future Directions
There is a need for rapid, cheap identification systems suitable for identifying individual livestock. Cattle rustling and the illegal movement of livestock (which is associated with fraudulent subsidy and compensation claims) are both big problems in many parts of the world and involve millions of pounds on an annual basis. In addition, the illegal movement of animals can present serious risks in spreading diseases, some of which can also infect humans. Furthermore, following natural disasters, such as flooding, animals can stray and in the absence of a means of permanent identification, there is the opportunity for theft and confusion.
The cost of molecular biological techniques is likely to decrease in future years, whilst their speed will increase because of the expanding demand for cheap, quick and sensitive methodologies. Consequently, the use of molecular methods for the identification of both species and individual animals is likely to become more widespread as their use becomes financially acceptable. Animal DNA databases are unlikely to raise the same ethical issues as human DNA databases, although they would require the same rigorous standards concerning the collection, analysis, and storage of information. Retinal identification systems have been trialled with racehorses, although these have suffered from practical problems and iris scans may be more effective (Cordes 2000). It would be interesting to evaluate the usefulness of these techniques for other high‐value animals. However, retinal and iris identification systems are only effective whilst animals are alive.
Stable isotope techniques hold great promise for determining the geographical origin of all sorts of biological material from bones to illegal drugs. Once reliable databases become available, these techniques will undoubtedly be used more frequently. Similarly, stable isotopes could be used to establish whether an organism was collected from the wild rather than raised in captivity or cultivated. This is relevant for distinguishing meat derived from animals raised in captivity on game farms from those that are poached. Similarly, in the exotic pet trade, it could differentiate between captive born and animals caught in the wild.