The typical modern crime lab is more functional and less glamorous than its television counterparts
Digital technology has transformed the traditional forensic lab. It is now possible to digitally reconstruct a crime scene so that investigators can determine the trajectory of bullets or recreate events that took place before police arrived on the scene. Computerised databases offer the chance to compare thousands of fingerprint, DNA and ballistic specimens and come up with a positive match within minutes. Using specialist software, forensic anthropologists can reconstruct a victim's face from their skull in a matter of hours, a process that used to take a skilled sculptor days to complete. Digital technology can also help recover vital clues from indistinct surveillance camera footage and from audio recordings, isolating crucial details that would otherwise have been lost.
A typical modern crime lab facility will include separate areas for DNA analysis, ballistics, trace elements and fingerprints plus a garage for stripping down vehicles, an evidence locker for storing items relating to a current investigation and a layout room for examining large items such as carpets, curtains and furniture. The latter doubles as a conference room where the team can meet to review evidence together.
THE DNA LAB
The DNA Laboratory is the heart of the modern crime lab. One microscopic sample of DNA can seal a suspect's fate, eliminating an individual from the investigation or giving the police sufficient cause for an arrest. Once a sample of DNA has been obtained from a suspect (either voluntarily or under court order), it can be compared to blood, hair, saliva or semen samples recovered from the crime scene.
To prepare the DNA for analysis the lab technician will put the sample in solution, using a micropipette which delivers precise amounts of the liquid agent. Then the sample is placed in a centrifuge which separates it into its component parts. If unidentified blood, saliva or ephithelial cells (skin fragments) are recovered they can be put through a ABI 310 Genetic analyzer to identify the genetic makeup of the owner. The resulting DNA profile can then be compared to the many thousands obtained from offenders on the CODIS (Combined DNA Index System) database in the hope of finding a match.
The typical modern crime lab is more functional and less glamorous than its television counterparts
Until the advent of genetic fingerprinting paternity cases were determined using blood samples
Without a doubt, the most significant development in the evolution of forensic science was the discovery of genetic fingerprinting, or DNA profiling as it is more commonly called. Unfortunately, DNA analysis is not as fast a process as fictional crime shows would have us believe, nor can it distinguish between identical twins, but in all other respects the technique has armed law-enforcement agencies with a dependable tool for putting a name to otherwise unidentifiable human remains and placing suspects at a crime scene. And often from the smallest fragment of trace evidence – DNA can be taken from a single hair (provided that it still retains the root), a scraping of skin from under a victim's fingernails, a swab of saliva obtained from a suspect's mouth, a single drop of blood or a semen stain on the victim's clothes.
The discovery of DNA, the genetic code that determines human gender and physical characteristics, was made by two British scientists, Watson and Crick, in the 1950s. However, it wasn't until 1984 that another British scientist, Dr Alec Jeffreys, identified a series of repeated sequences within every strand of DNA that are unique to each individual, making it a far more practical system for identification than traditional fingerprinting. Initially it was seen as a significant development in helping to determine paternity suits which until that time had been resolved using blood tests which only indicated a probability of a biological link. DNA fingerprinting, however, could provide a definitive answer with odds of approximately three million to one that the sample would match someone other than the person profiled. At a single stroke the judicial system had a means of determining innocence or guilt in cases where there was 'reasonable doubt'. The discovery promised miscarriages of justice would be a thing of the past and decade-old cold cases would be solved provided the trace evidence had been preserved. However, its practical application had first to be proven in a court of law and accepted by the public.
DNA samples are subjected to analysis to reveal their distinctive 'bar code' pattern
DNA (deoxyribonucleic acid) is a genetic blueprint found inside the nucleus of every cell in our body and so is often referred to as the 'building block of life'.
DNA fingerprinting involves extracting a sample of DNA from bodily fluid such as blood, semen or urine, hair follicles, tissue samples or skin cells (known as epithelials) and analysing one particular region of the DNA strand known as STRs (Short Tandem Repeats) because it is only this section which determines individual, distinctive physical characteristics such as hair colour and facial features. The rest of the strand is concerned with more general genetic information common to all human beings.
STRs vary in length from person to person and, when treated with a radioactive probe, they produce an X-ray pattern similar to a barcode with a mixture of thick and thin black lines which can then be compared to those taken from a crime scene or a victim to ascertain whether they match. The process can be compared to scanning the same point in two different novels in the search for an identical sentence instead of having to read both books in their entirety to see how many times the same words recur.
DNA ANALYSIS
Inside the nucleus of each and every cell in the human body are 23 pairs of chromosomes made of deoxyribonucleic acid (DNA). Each DNA molecule contains four chemical units: Adenine (A), Guanine (G), Cytosine (C) and Thymine (T) which comprise its protein and enzyme elements and are paired in chromosomal strands known as a double-stranded helix which looks like a contorted ladder. DNA is coiled like a spring inside the cell, but if unwound each molecule of DNA would stretch almost to almost 1.8m (6ft) in length. The variations in the base sequence which determine our unique personal physical characteristics and our development are called polymorphisms because they vary from person to person. The unique 'bar code' created by the base pairs known as VNTRs (Variable Number of Tandem Repeats) makes it possible to make a genetic identification.
First the DNA has to be separated from protein and other material attached to it in a process known as extraction. There are two methods of achieving this. The first is called Restrictive Fragment Length Polymorphisms (RFLP) analysis, the second is Polymerase Chain Reaction, or PCR.
A DNA expert gives evidence in the O. J. Simpson case
In RFLP analysis the extracted DNA is combined with a 'restriction enzyme' which breaks up the DNA strand into several components. These pieces are immersed in a gel to split the double-sided pieces into single strands. Then electrical current is applied (electrophoresis) which forces the negatively charged pieces to accelerate through the gel at varying rates toward the positive pole, thereby separating the strands according to size.
Using a nylon membrane, the fragments are lifted from the gel and are 'fixed' to the membrane with heat or allowed to dry. The four chemical components of each molecule (the A, T, C, and G bases of the strand) are now exposed and treated with a radioactive synthetic genetic probe made of a single strand of DNA. This is attracted to its complementary base; when it adheres to the base it forms a pattern which can be picked up using a sophisticated form of X-ray known as an autoradiograph and a print run off for comparison with 'bar code' strips sourced from other people.
Today it is becoming more common to use a chemical agent instead of radiation to illuminate the latent pattern, which takes only a matter of hours instead of days.
As with physical fingerprints, samples are matched using statistical probability meaning that a DNA sample with four identifiable fragments is statistically more reliable than a sample with three, but both can be of crucial importance in cracking a case. The chance of any two individuals sharing the same DNA can be as high as one in several billion, which means DNA can determine the outcome of a case far more effectively than conventional fingerprinting.
The PCR process replicates the cell's production of DNA
The PCR process (also known as molecular xeroxing because it works by replicating the cell's production of DNA) is less precise, but it can produce valid results from a minute specimen, whereas RFLP requires a significantly larger sample for testing and if the sample is degraded it is unlikely to produce sufficient data to produce a positive match.
In the PCR process the extracted DNA is heated in a thermocycler which forces the elements to split into their component parts. The temperature is repeatedly altered and chemicals added to highlight a specific part of the DNA strand and make millions of copies which are known as amplified DNA. Then a typing protocol, or profile, identifies the distinctive lines of the genetic bar code so that a match can be made.
The success of DNA testing in America has resulted in the establishment of a central DNA data bank known as the National DNA Index System (NDIS), but the specimens are limited to specific categories of criminals who are compelled by law to donate samples in the belief that they are likely to reoffend or to have been responsible for previously unsolved cold cases which may be reopened in the future.
THE TRACE LAB
A single hair, fibre, scrap of fabric or sliver of paint can be enough to convict the guilty. By comparing trace evidence found at the scene with samples taken from the suspect, their vehicle or their home investigators can make a match using a Comparison Polarized Light Microscope that could prove conclusive in court.
For looking at objects in 3D and in fine detail investigators will use a stereo microscope. A good example of this would be if they were looking to match a roll of gaffer tape from the suspect's home with a strip of tape that had been used to gag a victim. The stereo microscope would reveal if the gag had been cut or torn from the roll recovered from the suspect.
If it is thought that there might be trace elements of drugs or explosives in material found at a scene it is possible to separate these for further analysis using a Gas Chromatograph Mass Spectrometer.
Cases that had baffled detectives for years have been finally solved by a new aid to detection known as an Infrared Micro Spectrophotometer, which analyzes the vibrational rate of compounds to identify their molecular structure. A few grains of soil scraped from a suspect's shoe or the tyre of a car can be enough to provide a molecular profile which then can be used by detectives to prove that their suspect was at the murder scene (see 'Driven To Murder' here).
A single hair can be enough to convict the guilty
The various types of microscope, now highly developed, have always been crucial in forensic science, bringing the guilty to justice by revealing evidence that is invisible without their aid. Identifying trace evidence may be taxing work, but it can provide the conclusive proof that nails down a case.
PAINT
To the naked eye a freshly spray-painted car might look brand new, but a thin scraping of paint examined under a powerful scanning electron microscope (SEM) can betray the fact that it has recently been resprayed to erase evidence of a hit-and-run incident.
An SEM is capable of magnifying the smallest measurable area, known as a nanometer, which is 100,000 times smaller than the width of a pin, to reveal multiple layers of paint and the order in which they were applied. Fortunately for forensic scientists, each manufacturer mixes their paint to specific formulae so that no two shades are exactly the same, although they may appear so to the naked eye. By subjecting samples from suspect vehicles to microspectrophotometry, which analyzes the wavelengths of light emitted and absorbed by a single fleck of paint, lab technicians can identify its chemical composition which will provide a positive match to a specific make and model and even name the year it rolled off the assembly line. From there it should be comparatively easy to find a positive match among the suspect vehicles and thereafter a thorough examination should provide more trace evidence such as clothes, fibres and blood to place the car at the crime scene.
Two British police forensic experts examine a car at the scene of a fatal stabbing
The typical crime scene will be littered with numerous fibres, some of which (such as cotton) may be too common to be useful to the CSI. But the trained eye will swiftly identify which strands to collect for analysis and back at the lab technicians will be able to separate synthetic from natural and animal hairs from human.
Forensic scentists can determine useful information about the race, sex and age of the owner of the human fibres. Having determined their origin, the lab technicians can then identify which part of the body a human hair came from, as the shape of each type varies significantly. The cross-section of a hair pulled from the head will be round, as opposed to a beard hair which is triangular and eyelashes which tend to be tapered.
Animal fibres vary in thickness but all have scales, which distinguish them from human hair. A burglar, for example, who leaves minute traces of dog hair at the scene after he brushes against the soft fabric of a curtain or sofa can be more easily traced once the breed of dog has been identified and matched to its owner. Killers have also been tracked down through plant fibres to specific locations where that particular specimen grows naturally or, in one case, where the perpetrator worked in a garden supplies centre. In such cases it might be necessary for investigators to consult a botanical expert.
Plant fibres have their own unique shapes and textures so that even after being chemically treated and dyed by the clothing or furniture manufacturer it is still relatively simple to identify them. Even the dye can be identified using microspectrophotometry or thin-layer chromatography (see here).
Synthetic fibres are more problematic as their method of manufacture means that they will all be uniformly regular, although texture, shape, solubility and chemical constituency should help to identify the manufacturer and from that the retail outlet where the item was purchased.
These diatoms (microscopic single-celled algae) were found on the clothing of a suspected burglar
Similarly, glass may look smooth and featureless to the naked eye, but under the microscope each fragment reveals its distinctive density and structure which could lead investigators to the manufacturer and ultimately to the suspect. A thick pane of window glass, for example, will bend light to a different degree than a beer glass so it would be easy to determine whether a splinter of glass found on a suspect's clothing had come from a bar-room fight or from their work place, as they might have claimed. The refractive index (that is, the degree to which it bends light) of a sample shard of glass is measured either by a laser or by the traditional method of immersing it in a special oil which alters the refractive index when heated to a certain temperature. If the sample reacts to the heated oil at the same temperature as the glass found at the crime scene it is considered a positive match.
But even then the result needs to be confirmed by determining a second factor, the density of the glass. This is achieved by immersing the sample in two different liquids with different densities (such as water and liquid gelatin). Obviously even the smallest sliver of glass will sink in the former and float in the latter, so the lab technicians mix the two liquids until they have a solution in which the sample remains where it settles and this reveals the density of the glass.
Under the microscope each glass fragment reveals its distinctive density and structure
The law makes a significant distinction between someone who accidentally causes the death of another person and an individual who causes a death while high on drugs or alcohol. Proving the presence of toxins in the blood of the accused is therefore crucial to the prosecution case. Both crimes are categorized as manslaughter, but the presence of an illegal amount of alcohol or drugs may prove either negligence or 'wilful disregard for human life' which would determine the severity of the sentence.
In Britain, police routinely administer a breathalyzer test at the roadside which measures the amount of alcohol in the moisture droplets contained in a driver's breath, but the results are not admissible in court. If the test proves positive a more detailed analysis will be made at the lab from a urine sample taken at the police station. A similar test for illegal drugs using an immunoassay kit can be administered to suspects once they are in custody. If there are chemicals in the urine they will cause a reaction when combined with the artificial antibodies in the kit, producing a colour change which indicates the presence of toxins. However, a more thorough lab test is necessary to determine what those toxins might be.
In the lab the presence of both drugs and alcohol is tested in the same way, using gas chromatography to isolate toxins from the natural chemicals contained in the urine. First the sample is vapourized and mixed with a neutral carrier gas (normally nitrogen) then passed through a perspex tube filled with granules which acts as a filter.
The rate at which the constituent parts of the vapourized gas reach the sensor at the end of the tube is measured and their speed reveals the identity of the individual elements which are shown as peaks of various intensity on a digital graphic display. The gas chromatograph is usually augmented by a mass spectrometer which isolates the charged particles (ions), which can then be measured to create a spectrum which identifies their chemical composition.
Alternative methods include high-performance liquid chromatography, which requires a liquid carrier, and thin-layer chromatography, in which a specially coated glass sheet is dipped into a liquid sample of fluid obtained from the suspect which separates into its component parts as it is absorbed by the coating. These components can then be seen as a vertical line of discoloured spots creeping up the sheet in parallel to a control sample containing the drugs the lab are looking for. If the suspect's sample produces an identical pattern to the control sample, it proves the presence of the control drug.
Poison is a staple ingredient of classic Victorian crime fiction and a feature of many of the most notorious murder cases of the 19th century, but the lethal science did not go out of fashion with Hansom cabs and crinoline dresses. Even now jealous spouses and spurned lovers poison their partners, fatal drug overdoses (intentional and otherwise) claim dozens of lives a day around the world and occasionally multi-million dollar civil cases come before the courts alleging that irresponsible companies have poisoned innocent people by tipping toxic waste into drinking water, or burying it on landfill sites which are later bought for residential development.
Despite the advances in forensic technology the most reliable method for detecting the presence of poison in the human body is the traditional method, analysing a single strand of hair from the head of the victim. Not only will the test reveal the existence of fatal toxins but also the history of poisoning as indicated in the discoloured stripes along each strand, rather like the graded bands of coloured earth in geological samples.
Solvents and other hazardous chemicals will collect in the lungs while morphine, heroin and anti-depressants are likely to be detected in blood and liver, so if the coroner suspects suicide or an accidental overdose the pathologist will send samples of blood and bile to the lab for analysis using chromatography or the immunoassay method.
FIREARMS LAB
The most imposing piece of equipment in this department is the water tank into which bullets from a suspect's weapon are fired. The water slows the projectile and prevents it from being damaged as the unique rifling and striations marks must be preserved.
Bullets and shell casings recovered from a crime scene can be scanned into a computer provided that they are still intact. However, bullets embedded in walls and doors are usually too distorted or damaged to be identifiable.
If they are lucky enough to have a bullet or casing from the crime scene and another from the suspect's gun, investigators can make a direct comparison by placing them side by side under a comparison microscope to see if the striations match. If they match, then they know that both were fired from the same gun. Otherwise they have a chance of tracing the weapon by searching a ballistic database known as IBIS (Integrated Ballistics Imaging System) with which they can compare the distinctive markings on bullets and shell casings in the hope of finding a match.
Major crime labs carry a large stock of assorted firearms for reference. Most of these weapons will have been recovered from convicted criminals.
The water tank in a firearms lab helps CSIs identify if a particular gun was used in a crime
THE FINGERPRINT LAB
In allowing for a fast, on-the-spot treatment process, the Vacuum Metal Deposition Chamber is one of the most useful pieces of equipment in the fight against crime. If investigators suspect that there might be a fingerprint or palm print on an item that they can't lift a print from in the usual way, they can put the object in this machine. It sucks all the air out of the chamber, creating a vacuum, then coats the object in a fine layer of gold, revealing the pattern of the print.
Fingerprints which are not removable can instead be photographed then scanned into a computer to be compared with those registered on the database.
Walk into any forensic AV lab and you could be forgiven for thinking you had wandered into a multi-million-dollar recording studio. State-of-the-art digital AV equipment has been a feature of film and TV post-production suites for decades, but since the early 1990s high-budgeted crime labs have acquired audio and visual recovery software in order to be able to enhance potentially significant details from low-quality surveillance cameras and to filter unwanted background noise from ransom tapes. Voice print programs are also occasionally used to isolate a criminal's voice pattern, which can then be displayed visually on a computer screen so that a comparison can be made with sound samples obtained from suspects in the hope of obtaining a good match.
Much of this digital technology currently in daily use by well-funded crime labs was originally developed by the aerospace industry. It has enabled investigators to recover images and identify voices that would have been impossible to salvage from analogue sources, but even digital technology has its limitations, one of these being the fact that every aspect of the technical process must be recorded in detail if it is to be admissible in court to ensure that it supports the facts and does not merely speculate on what might have happened.
VIDEO ENHANCEMENT
It is estimated that in major population areas the average person is captured on some form of surveillance equipment 20 times every day, which has led to security cameras becoming a prime source for tracking a suspect's movements. Unfortunately, most surveillance cameras are of poor quality, so to enhance the images forensic AV technicians utilize video enhancement software which filters out unwanted 'noise' and sharpens a selected area of the screen by filling in the missing or corrupted information which is distorting the image.
HUF Transform technology enables investigators not only to filter out corrupted data but also to manipulate a distorted section of the frame in order to bring out a specific detail. By calculating a rotation angle which will normalize the image when it is digitally distorted it can be viewed as if it had originally been photographed from this angle. In this way it is theoretically possible to read the number plate on a car parked at a skewed angle to the camera, or turn a suspect 180 degrees to see if he is carrying a rifle or an umbrella.
Vital clues can also be found in amateur footage, which is why whenever there is a major terrorist incident anywhere in the world the authorities issue a request for all tourist photographs and videos of the incident to be handed in for analysis. Obviously, there is a limit to the amount of detail that can be obtained during enlargement at high magnification even from digital data, especially when there is a low level of lighting or when the subject is moving, but it has been known to help investigators read a numberplate from a suspect's car caught on a speed camera and to catch the flash of a knife later thrown away by a killer who claimed not to have been armed during a fatal fight.
Digital also has the inherent problem of pixilation (the artefacts which comprise the image), which increases with each level of magnification, making the image look like a mosaic. But it is still a considerable improvement over the traditional method of photographic enlargement, which would produce a blurred image at a far lower level of magnification.
CRIME SCENE RECONSTRUCTION SOFTWARE
CSR software has been compared to the creation of a movie trailer where only the highlights are known and the details are left to the viewer's imagination. For a reconstruction to be valid, accurate measurements have to programmed into the computer so that various possible scenarios can be replayed until one is found that fits the facts and the scene as the police found it. If, for example, a man was found drowned in his backyard swimming pool fully clothed with a ladder lying nearby it could be assumed that he fell backwards while repairing something on the outside of his house, taking the ladder with him. CSR software would programme in his height, the distance from the body to the house, the length of the ladder, the angles and distances between each significant object and so forth. When the scene is replayed the man and the ladder should end up where they were found in real life. If not, then another scenario needs to be considered, such as the possibility that the scene was staged.
More commonly CSR is used in determining the train of events in fatal road accidents, where a vehicle's speed can be factored in using the thickness of the skid marks and the distance a second vehicle or body was found from the point of impact.
AUDIO ISOLATION AND RESTORATION
When an audio recording of a ransom demand or a threatening phone call is brought into the lab there are a number of processes it can be subjected to in order to isolate the caller's voice and also the background noise which may hold significant clues as to their location. If, for example, a recording has been made in a busy railway station the crucial voice or voices can be brought sharply into focus by rolling off the bass frequencies to eliminate unwanted rumbling and booming from the passing trains. Reducing the high-end frequencies can also lessen the presence of background conversation which occupies the top end of the dynamic range and compression can be applied to push the desired voice to the foreground.
But these are not the only occasions when such specialized audio enhancement software might be used. A car caught on tape during a hit and run accident or a drive-by shooting, for example, could be identified from the engine noise although it would require a CSI with specialist knowledge to do so as there is currently no database from which to make a comparison.
Thanks to state-of-the-art digital audio technology, even damaged or partly erased data from an audio tape can be recovered so that a crucial conversation between two conspirators, for example, could be restored and used as evidence. The tape would be transferred to digital and the audio file cleaned up using filters which reduce hiss, rumbling and distortion. Then it could be treated with compression and equalization as described above to isolate and identify a particular voice or a sound.
A policeman secures a street as a body lies on the ground in Santa Monica, California
In the 1950s London's traffic was considerably less chaotic than it is today, but even so pedestrians and cyclists could not afford to be complacent during the rush hour. After a female cyclist was hit and seriously injured by a careless motorist who failed to stop, police launched a city-wide search for the car. Witnesses described having seen a black Austin with the letters PN on the number plate speeding away, but there was little hope of tracking the driver down since it was a mass-produced model of a popular make and colour. But then police found a single flake of black paint on the bike's handlebar. This was subjected to microscopic analysis and shown to comprise four layers: two black and, below those, two green. Vaporized in a spectroscope, the flake produced an emission spectrum consistent with cellulose paint, the type used on motor vehicles of the period.
With no computer database to help shorten their search, detectives were forced to thumb through several thousand card index files in search of every Austin registered in the capital answering to the description. Nine were eventually identified and policemen on the beat were despatched to question the owners. All could prove that they were far from the scene at that time except for one, a man named Cameron who lived in Ealing and whose route home from work took him past the scene of the accident. While examining his car the constable noticed that the right wing had recently been retouched. The constable's suspicions were confirmed when he happened to see Cameron looking agitated in the mirror.
On closer inspection the constable found a few woollen strands stuck to the wing mirrors and took them back to the lab. Under the spectrophotometer these proved to be identical to those in the cardigan the cyclist had been wearing. More damning was a sample scraping of paint from the car which the spectroscope revealed to have the same composition as the flake taken from the handlebar. Faced with such incontrovertible evidence, Cameron admitted his guilt and was sentenced to three months in prison for failing to stop after an accident.
Tweezers extracting paint from a damaged car
On the evening of 21 March 1962 Mr and Mrs Miller returned home to find that their 15-year-old daughter Marilyn had disappeared without a trace. Police searched the area and within hours found the girl's body face down in a reservoir behind the house. They also found footprints and tyre tracks on the dirt road nearby, together with a pair of discarded workman's gloves and a belt. No one in the neighbourhood had seen or heard anything unusual, although one of Marilyn's school friends remembered seeing a black and turquoise 1953 model Plymouth parked near the Miller house earlier that night.
The car was later found abandoned and inside was a pair of boots which matched the footprints on the dirt road. The boots were a lucky break for the detectives because they had been repaired using the heel from another pair of boots, which meant they produced a unique set of prints. Even more remarkably, the tyre was found to have a manufacturer's flaw which created highly distinctive tracks that matched the impressions found at the scene.
All the police had to do was trace the owner of the vehicle and they would have an open-and-shut case. Or so they thought.
The vehicle was registered to a local dairy worker, Booker T. Hillery Jnr, who had recently been released from prison where he had been serving time for rape. He was immediately arrested and charged with murder. During the course of the investigation the gloves were also identified as belonging to Hillery, which seemed to tie up the case for the prosecution and leave no room for reasonable doubt.
Hillery was convicted and sentenced to death. But the authorities had reckoned without Hillery's dogged determination to forestall the inevitable and an ironic twist of fate.
Through a succession of appeals Hillery managed to keep delaying the execution until 1974 when the US Supreme Court decided to abolish the death penalty. It was later reinstated but by then it was too late: Hillery's life sentence could not be revoked. Clearly Hillery was a shrewd and cunning killer whose sense of self-preservation outweighed any feelings of remorse.
Booker T. Hillery, right, is led into Kings County courtroom where he was convicted of the murder of 15-year-old Marilyn Miller
In 1978, not content with escaping the electric chair, Hillery successfully filed for a retrial on the grounds that African-Americans had been deliberately excluded from serving on the Grand Jury in Kings County in 1962. It was a clever ploy because if Hillery could force a retrial he might be able to sow sufficient doubt to secure his release. Time had strengthened his hand. Of the original 24 witnesses, 21 were dead, and the forensic evidence could be disputed on the grounds that the tyre and boot tracks only proved that Hillery was in the vicinity of the Miller house. There was no irrefutable proof that he was actually inside their home. The date for a second trail was set and prosecutors had to present a convincing case or be prepared to drop the charge and see Hillery walk free – perhaps even sue the state for wrongful imprisonment. It was then that they had a lucky break.
But just before the case came to court, investigators discovered that a resourceful detective had asked Marilyn's mother to hoover her daughter's bedroom on the night of the murder in case there were microscopic trace elements which could prove vital in the case. These had miraculously survived in the police archive, and now this bag of dust and dirt was put under the microscope. It was found to contain tiny blue spherical paint particles of the kind produced by a spray can. Normally, when paint is sprayed on a flat surface, the particles flatten out, but these were round because they had been sprayed onto fabric. In fact, minute traces of cotton could be seen sticking to the paint.
On a hunch, detectives retrieved Hillery's clothes from the evidence store and found matching blue paint particles on his clothes that placed him at the scene on the night of the murder. They traced the paint to the interior of Hillery's car, which he had sprayed with this distinctive Prussian Blue pigment. Evidently minute particles had fallen onto him while he was driving and some of these were shaken off in his struggle with Marilyn. The irony is that Hillery had prevented the county from selling his car after the first trial in 1962 by threatening to sue them for disposing of his property, so it was still impounded 24 years later, a time capsule of perfectly preserved forensic evidence.
Twenty-five-year-old evidence had finally nailed a careless killer, and Hillery's bull-headed belligerence cost him another 25 years to life behind bars with no prospect of parole.
Even in the early days of forensic science it was recognised that a single strand of hair or fibre could contain enough evidence to convict the most cunning and calculating killer. The case of Johnny Fiorenza is a prime example.
In 1936 Nancy Titterton, a 33-year-old writer, was discovered dead in the New York apartment she shared with her husband, NBC executive Lewis Titterton. Her naked body had been found by two furniture delivery men lying face down in an empty bath with a pyjama jacket knotted round her throat and her underclothes scattered across the bedroom floor, indicating that the motive had been sexual.
On his first visit to the crime scene Assistant Chief Inspector John Lyons was optimistic of making an early arrest as the killer had been careless: in his haste to escape he had left behind part of a length of cord used to bind the victim's wrists, which might be traced back to him. Muddy footprints on the carpet were initially ignored, as a preliminary examination revealed that they contained traces of lint such as might be found in furniture manufacture and they were therefore attributed to the delivery men.
However, the search for the cord uncovered the fact that a New York wholesaler had sold a roll of it to the very same furniture store which had delivered a chair to Mrs Titterton on the afternoon of the murder. Then the city crime lab discovered an unusual hair on the bedspread where the rape had taken place. A microscopic examination revealed it to be horsehair of the type used in furniture upholstery.
Held firmly by two detectives, Johnny Fiorenza, centre, is led to the apartment in New York where the crime was re-enacted
As both delivery men had arrived at the apartment together Inspector Lyons assumed that one of them must have gone there earlier; Mrs Titterton would have let him in as both men had visited the apartment on several previous occasions. When Lyons called at the furniture store he questioned the proprietor, who had been one of the two men to discover Mrs Titterton's body and who could account for his whereabouts on the morning of the murder. His assistant, however, had been absent from the shop and claimed to have been visiting his probation officer at the time. But, as Inspector Lyons discovered, the probation office was closed that morning for the Easter holiday.
When confronted with the evidence Johnny Fiorenza broke down and confessed. It seems likely that he placed Mrs Titterton in the bath not to revive her, but to cover himself in the event that he was caught when he would claim that her death had been an accident. But the judge and jury saw it as a cunning act of self-preservation and sent Fiorenza to the electric chair.
Faced with the evidence, Fiorenza confessed to the the murder of Nancy Titterton
The 24-year-old upholsterer's assistant, an ex-convict, in New York following his arrest
When 33-year-old Ohio paramedic Michelle Baker became pregnant, her live-in lover, soft-spoken and charming medical resident Maynard Muntzing, seemed genuinely delighted and offered to celebrate with a dream wedding on a tropical island paradise. But unbeknown to Michelle, Dr Muntzing secretly entertained hopes of being reunited with his former lover Tammy Erwin, and saw the baby as a hindrance to his love life. Nevertheless the couple flew to the island as planned, where Muntzing invented an excuse for postponing the ceremony. Michelle then began to suffer severe cramps and some light bleeding which she attributed to food poisoning or a local bug. On her return to Ohio she consulted her own doctor, who reassured her that nothing was amiss.
Michelle was initially delighted when Muntzing purchased a luxury home in which to raise his new family. But the cramps and bleeding continued, causing the expectant mother considerable anxiety. She then happened to hear a record request on her local radio station for a listener named Maynard whose voice was eerily familiar. Maynard was supposedly on vacation in Columbus at the time! Her curiosity aroused, Michelle drove to Tammy's home where she found her fiancé and his ex-girlfriend together.
A confrontation ensued, but Michelle was persuaded that the amorous doctor was committed to her and the baby and that his affection for Tammy was in the past. However, the nausea, cramps and bleeding continued, forcing Michelle to conclude she was being poisoned. She managed to smuggle a drink Maynard had made her to the police, whereupon it was proven to contain cytotec, a drug used to treat stomach ulcers which was expressly forbidden for pregnant women since it was likely to cause an abortion. But as detectives pointed out, there was no proof that Dr Muntzing had put it there; Michelle could have put it in her own drink to discredit her two-timing lover.
It was only when Michelle returned with a video she had made showing Dr Muntzing putting something in her drink that the police were forced to test her story. They too set up a secret camera in her kitchen which they monitored from the garage and thus they were witness to Muntzing mixing one of his mysterious cocktails while Michelle was out of the room.
They immediately rushed into the house and arrested Muntzing. The drink was analyzed and found to contain yet more cytotec. More vials of the drug were found in his car. Muntzing was charged with the attempted murder of an unborn baby, but the case never came to court. Unfortunately the prolonged, insidious poisoning had affected Michelle's health and just weeks before the trial she gave birth to a stillborn child.
Maynard cut a deal and spent five years in jail in addition to losing his medical license. He might still be there today had it not been for the fact that no cytotec was found in the placenta after the birth and Michelle's failing health meant that she was not able to take the witness stand during what might have been a lengthy trial.
Michelle Baker who was poisoned by her live-in lover
Suspicion comes naturally to crime scene investigators, who are trained to question everything – especially when there is a dead body at the scene and someone has benefited financially from the demise of the deceased. This is as true now as it was back in 1850, when Gustave Fougnies, the son of a wealthy Belgian apothecary, was found dead on the dining-room floor at his sister's house.
Gustave had been in poor health for many years and the recent amputation of a leg would normally have been considered a contributing factor to his early death. But the local magistrate was uneasy. Instead of taking on the pallid appearance of death, Gustave's corpse looked flushed and, on closer examination, his throat and mouth were found to have turned deep red as if they had been burnt.
The dead man's hosts, his sister Lydie and her husband Count Hyppolyte de Bocarme, were both deeply in debt and had been expecting to inherit her father's money until Gustave had announced his intention to marry, which would have left them with no prospect of paying off their creditors.
In due course the servants were questioned and described the curious events which followed the death of their guest. The Count had ordered a servant to bring a bottle of vinegar, which he emptied down the dead man's throat claiming that it would revive him. When it failed to do so, the Count had the body stripped and the clothes soaked in boiling water. More vinegar was summoned to wash the corpse and then the Count and Countess got down on their knees and scrubbed the dining-room floor.
The magistrate also learned that the Countess had served the meal herself, having first sent her children to eat in the nursery, which was unusual given that the dinner guest was their uncle.
ENTER THE EXPERT
A post-mortem was ordered and the stomach contents sent to Jean Servais Stas, a young chemistry professor in the capital. Stas was to become a seminal figure in the history of toxicology through his work on vegetable poisons. He immediately recognised that the vinegar was not strong enough to have caused the burning to the throat and mouth and so must have been used to disguise another more readily detectable toxin. By mixing the stomach contents in a solution of alcohol and then water Stas was able to filter out the foreign substance, which produced a distinctive acrid smell. It was nicotine, which in its pure state is a deadly poison comparable to prussic acid. Stas then mixed the dissolved nicotine with ether and allowed the ether to evaporate, leaving a flask of transparent oil which smelt and tasted of tobacco – enough to despatch several healthy men. The problem now was how to prove that it had been administered by the dead man's hosts.
The Count, it transpired, was something of an amateur chemist and possessed his own laboratory. He had gambled on the fact that vegetable poisons were undetectable, but he had reckoned without the indefatigable Stas, who was keen to solve that particular problem. Having distilled the colourless liquid from tobacco leaves the count had wrestled his brother-in-law to the ground and held him down while sister Lydie had poured the poison down her brother's throat. Traces of nicotine were subsequently found on the dining room floor. So strong had the liquid distillate been that even the scrubbing could not eliminate it entirely.
A deadly poison: amounts over 40mg can cause death
If the Count had intended the vinegar to mask the smell of the nicotine he failed. It was the acidic reaction of the two which caused the burns that had initially alerted the magistrate's suspicions. Moreover, when the vinegar was mixed with the alcohol in which the stomach contents had been preserved, it dissolved natural body substances leaving only the poison for Stas to distil. Ironically the Count, the amateur chemist who had used his knowledge for personal gain, had unwittingly discovered the formula for detecting vegetable poisons in the human body and had himself been detected by the one man capable of recognizing its potential.
In 1971 rumours began circulating in the American media that eccentric billionaire industrialist Howard Hughes (subject of Martin Scorsese's Academy Award-winning movie The Aviator) had finally broken his 30-year silence to tell his life story to a comparatively unknown writer, Clifford Irving. Among Hughes' surviving friends surprise was mixed with incredulity and even suspicion that the story may have been a hoax since Hughes was a resolute recluse who had guarded his privacy as fiercely as he had protected himself from the germs he feared would infect him if he allowed contact with the outside world.
For decades he had remained in self-imposed exile on his palatial island paradise in the Bahamas, where he reputedly refused to have his hair cut or to trim his fingernails so that he now had the appearance of an ancient Chinese mandarin with waist-length hair and nails 20cm (8 inches) long.
Irving's publishers, McGraw-Hill, had reservations of their own, but these were allayed when Irving produced a sheaf of letters allegedly written by Hughes which were subsequently declared genuine by handwriting experts. There was not yet any book on Howard's life to which he contributed and this would be an amazing publishing coup if it was authentic.
Duly satisfied, McGraw-Hill agreed to an advance of $765,000 which was an unprecedented amount at the time, but the company was convinced that they had secured an international best-seller. They handed Irving a cheque made out to H.R. Hughes which the author promised to forward to the reclusive billionaire and they awaited delivery of the manuscript. Irving did not disappoint them. In due course he delivered a weighty 1,200-page biography which was eagerly read by Hughes' former associates who declared themselves satisfied that the memoirs were genuine. They had the authentic 'voice' of Hughes – at least they did so on paper.
American industrialist, aviator and film producer Howard Hughes
VOICE OF A RECLUSE
Just as the presses were about to roll, associates of the billionaire announced that Hughes would be holding a teleconference at a Los Angeles hotel at which he would denounce Irving's biography as a work of 'fantastic fiction' and field questions from journalists who had known him in the early days.
During the two-hour session Hughes fielded a battery of probing enquiries which covered everything from technical details of the aeroplanes he had designed to trivial facts concerning the good luck charms given to him by female admirers. All were answered correctly. Then Hughes made a statement in which he denied collaborating with Irving or ever having met him. Furthermore, he wished it to be known that not a single cent of the $765,000 advance had been deposited in any of his many bank accounts. It was a convincing performance but there was still the question of whether the deep, resonant voice on the end of the phone line was genuine, or that of a well-informed impostor. There was only one way to find out.
Tapes of the conference were handed over to voiceprint analyst Lawrence Kersta, who compared the pitch, tone and intonation with an early recording of Hughes. Kersta's contention was that the underlying character of a person's voice remains constant even if the tone becomes frailer with age. After days of intense study Kersta declared himself to be convinced that the voice recorded at the teleconference was that of Hughes. But with a potential fortune at stake and the reputation of the publisher riding on the outcome it was decided that Kersta's verdict could not be considered conclusive, especially as he had a financial interest in the technology he had been using. The final word was then given to his fiercest critic, Dr Peter Ladefoged, professor of phonetics at UCLA, who had no vested interest in the outcome. Ladefoged subjected the tapes to detailed spectrographic analysis to compare the peaks and troughs of key consonants, vowels and phrases. He too announced that he was satisfied that the voice was that of Hughes.
The intense speculation surrounding the deal prompted Irving's Swiss bank to investigate the matter, after which they released a statement to the press confirming that a cheque for $650,000 had been deposited in the account of H. R. Hughes and then transferred to another in the name of Helga R. Hughes, Irving's wife.
Caught in a lie, Irving admitted his guilt and was sentenced to 30 months in prison. He was released after serving just 18 months and continued his career as a writer.
US writer, Clifford Irving, author of the fake Howard Hughes biography
The first true test of DNA fingerprinting came just three years after Dr Jeffrey discovered it, when police were investigating the rape and murder of two 15-year-old schoolgirls in the English Midlands. The first murder had occurred in November 1983, when schoolgirl Lynda Mann was found raped and strangled with her own scarf by a footpath in Narborough near Leicester. Fortunately, the police had enough foresight to preserve the semen stains, which revealed that the rapist was a Group A Secretor (someone whose blood type can be determined from other bodily fluids) with a pronounced phosphogluco-mutase (PGM) 1 + enzyme which is an identifying genetic marker.
But other than this they had no leads at all until July 1986, when another girl of the same age, Dawn Ashworth, was found raped and strangled 1.6km (1 mile) away from where the first victim had been discovered. A 17-year-old youth who had been seen in the area was questioned and charged. Under pressure he confessed and the police had no reason to believe that he was not telling the truth as he was able to tell them details that they believed only the killer could know. However, it transpired that he had chanced upon the body and so knew the murder scene at first hand and he shared the same blood type as the murderer, but he had not killed the victim.
Had it not been for the advent of genetic fingerprinting his presence near the scene at the time of the attack and his coerced confession might have been sufficient to convince a jury of his guilt and he would have spent the rest of his life behind bars. Fortunately, the police were aware of the radical new forensic technique and were willing to test it. They called on Dr Jeffreys, whose results caused consternation, as they showed Dawn and Lynda had indeed been raped by the same man but that the attacker could not have been the young man the police had charged. In fact, Dr Jeffreys carried out the test twice to ensure there could be no mistake. But that clearly wasn't the end of the matter.
Acting on the probability that the perpetrator was a local man, the police asked all men in the area of a certain age to donate a blood sample for testing. Every one obliged, but to the frustration of the police all 5,000 tests drew a blank. Either the test was not as conclusive as Dr Jeffreys had claimed, or someone had found a way to defraud the system. The future of DNA forensics lay in the balance until detectives received a phone call from a man informing them that a drinking partner of his had boasted that he had just given a blood sample to the Leicester police using another man's name. When interviewed, this individual, Ian Kelly, named the man who had paid him to give blood and said that he had only agreed because this 'friend' had convinced him that the police would stitch him up because he had a previous conviction for indecent exposure. The friend in question was one Colin Pitchfork.
After his arrest Pitchfork was required to give a blood sample which proved to be a perfect match with that of the rapist, but ironically he didn't wait for the result. Sensing the game was up, he confessed to both murders and subsequently received life imprisonment. His obliging friend, Ian Kelly, received an 18-month suspended sentence. But most significantly, the validity of genetic fingerprinting had been proven beyond reasonable doubt.
It wasn't the probing investigation undertaken by Washington Post reporters Woodward and Bernstein (played by Dustin Hoffman and Robert Redford in the movie All The Presidents Men) which led to the impeachment of US President Richard Nixon in 1974, but a single spool of cassette tape. Even as the high-ranking White House conspirators went down one by one like a row of dominoes, each accusing his immediate superior of ordering the crime and the subsequent cover-up, it looked as if Nixon might miraculously survive if members of his staff took the fall to preserve the Republican administration and what little was left of their leader's credibility. But then it became known that Nixon had ordered electronic bugging devices and voice-activated recording equipment to be planted in the Oval Office so that he could secretly record conversations with his own staff.
After much undignified haggling the beleaguered President was finally forced to hand over the tapes. To the dismay of his accusers nothing incriminating was found, although a lengthy segment was suspiciously silent during a conversation between Nixon and a senior White House aide. When questioned Nixon claimed that it had been accidentally erased. Undeterred investigators turned the tapes over to FBI forensic audio engineers who scrutinized the recordings for evidence that they had been doctored. Using comparatively primitive audio restoration techniques (which have since been superseded by digital software), the technicians discovered that the tape had been stopped and re-started 18 times, ruling out any chance that the record button might have been pressed accidentally. 'Tricky Dicky' had been caught out in a lie and was forced to leave the Oval Office under a cloud, narrowly avoiding imprisonment thanks to a pardon granted by his successor, Gerald Ford.
Dr Edward O. Heinrich, one of America's foremost forensic scientists, was a man of uncommon abilities. His expertise in several different forensic disciplines together with his instinctive sense for deception helped him to crack two thousand cases and establish a reputation as the man who could make the evidence talk.
In the summer of 1925 Heinrich took delivery of the charred remains of a corpse said to be that of Californian businessman Charles Schwartz, whose case had been referred to Heinrich by the victim's insurance company. Schwartz had apparently died in a fire at his makeshift laboratory in Walnut Creek. However, the insurance company needed confirmation that the body was that of their client as Schwartz had taken out a life insurance policy just before his death for the staggering sum of $185,000 and his widow was unable to supply a single photograph of her late husband for identification purposes. It appears that her home had been burgled the day after his death and the photographs were the only items stolen. Undeterred, Heinrich contacted a photographer in Oakland who had made a portrait of Schwartz some months before and asked him to make a new print from the negative.
Once he had the photograph for comparison Heinrich knew that he was not looking at the corpse of Charles Schwartz. The man in the photograph had a mole on his earlobe which the body before him did not possess. Under the microscope strands of hair found at the scene were clearly unlike those recovered from a hairbrush supplied by the widow. During the autopsy Heinrich discovered that the dead man's stomach contents did not match the meal Mrs Schwartz had cooked for her husband shortly before his death and his eyes had been gouged out and his fingerprints obliterated with acid to make identification more difficult.
So, if the body wasn't that of Schwartz, who was it? A search of his premises revealed partially burnt fragments of paper with the name 'G. W. Barbe' and the words 'Amarillo, Texas'. Barbe was the surname of a preacher who had been befriended by Schwartz and given a job as laboratory assistant at the Walnut Creek premises where artificial silk was to be manufactured. The material Schwartz claimed to have manufactured the day before his death was revealed to be real silk and the so-called laboratory was nothing of the sort. There was neither running water nor gas and the electricity bills were too low for a working lab. As for the body, Heinrich learnt that Barbe was of a strikingly similar build to Schwartz, but three inches taller – the same height as the corpse. Barbe's eyes had been blue whereas Schwartz's eyes were brown, a discrepancy which would account for the mutilation.
Convinced that Schwartz was alive and guilty of the murder of Barbe the California police ordered local newspapers to publish details of the case. The landlord of an Oakland boarding house recognized the description of the arson 'victim' and called the police. When an officer called to question the lodger, he found he had taken his own life. And this time there was no mistake as to the identity of the body. It was Schwarz, who had left a written confession and a belated plea for forgiveness.
An artificial silk factory of the 1920s: Schwartz's own so-called laboratory was nothing of the sort