Any schoolchild studying science for the first time will quickly understand the principle of scientific experiment and the concept of ‘a fair test’. This is a question which constantly challenges and I hope will continue to challenge the modern forensic scientist. Is it accurate? Is it reproducible? If we do it again will we get the same result? Is it based on sound research and review by the scientific community? And what does it mean? To the casual reader this may seem unimportant, but those accused or convicted of crime based on scientific evidence would have a different view. So it is a burden and a responsibility that anyone who practises forensic science should understand and embrace.
Less than a hundred years ago forensic science as we know it was barely recognisable. There are examples of scientific evidence being used in criminal trials going back centuries. An early example can be found in the term ‘caught red-handed’. This originates from the sixteenth century, but the earliest printed reference is attributed to Sir Walter Scott in his novel Ivanhoe, first printed in 1819. ‘Red-handed’ indicates finding the blood of the victim on the suspect. The assumption made is that the red liquid is blood, human blood, and from the victim. Even in the 1980s human blood could only be distinguished by a series of independent grouping systems, such as ABO, which a scientist could interpret and only then give, by today’s standards, limited statistical probability as to its origin. Not until the introduction of DNA technology in the late 1980s could the discrimination and probability of blood and other body fluids reach any high degree of certainty.
Early attempts by researchers such as Bertillon to identify and catalogue individuals by an elaborate system of anatomical measurement recognised that humans are all different. However, it was overtaken by the much more practical science of fingerprints. Fingerprints could be used to identify individuals and had the added bonus of being recoverable from the scenes of crime.
First used in a criminal case in London in 1902, fingerprints provide a ready and reliable method of identifying individual people. The basis of the system is the premise that no two individuals have the same finger, palm, or footprints. These are the areas of the human body where friction ridges can be found. The ridges are frequently broken by forks or stop at an ending (known technically as bifurcation and ridge endings). These breaks and endings are known as fingerprint characteristics.
Sir Edward Henry introduced the fingerprint system in Scotland Yard in 1900. A collection of inked finger impressions (fingerprints) formed the basis of the method of identifying individual convicted criminals along with their criminal record history. It exists to this day. Finger impressions (finger marks) recovered from crime scenes formed a later collection. At first manually stored and now computerised, these can be searched against the prints of those with previous convictions. It is a powerful tool only to be matched in its impact in the scientific investigation of crime by DNA technology, almost a century later.
The Frenchman Edmund Locard is the modern father of forensic science. In the early 1900s he formulated his ‘principle of exchange’ which is the cornerstone of the science to this day. He stated, ‘When two objects meet there is a mutual exchange of material from one to the other.’ It can be summarised to say ‘every contact leaves its trace.’ The challenge is to find it.
However, finding it is only the first part of the problem. Once found, we have to consider its meaning. Forensic science can be said to be the science that brings all science together and then brings it into the courtroom. Which is where the term forensic originates, its means ‘pertaining to the law’. Forensic science is the science of identification, contact and dynamic events. Above all it is a science of context. Many events which forensic science may detect can be ordinarily found, perhaps innocently, in everyday aspects of human endeavour. What makes these events evidence in a criminal trial is the context in which they are found. The finding of forensic evidence can indicate the presence, actions and consciousness of an individual at a time or place which supports their involvement in the commission of a crime. It can also exonerate, which is often its most important use.
The Metropolitan Police Forensic Science Laboratory opened in 1935 at Scotland Yard and marked the beginning of a planned use of forensic science in criminal investigation in the UK. Home Office laboratories followed to serve provincial forces. By 1959 a new profession of forensic science was establishing itself, prompting like-minded individuals to form the Forensic Science Society. Its aims were to ‘advance the study, application and standing of forensic science and to facilitate cooperation among persons interested in forensic science throughout the world’. It has been doing that pretty effectively ever since.
The specialised examination of the crime scene is an even more recent event. Until the 1950s in the UK and North America, the examination of the scene was the domain of the detective. Only rarely, in numbers which could be counted on one hand, would forensic scientists themselves examine a crime scene and then for a single purpose, most commonly for something like blood splashing. Pathologists had for many years examined the scene of sudden or suspicious death but their domain was that of forensic medicine and toxicology. It didn’t stop many of them from stepping into areas in which they had no training or experience. In the absence of dissent, their medical expertise in all matters forensic was accepted unopposed.
The regular and routine examination of crime scenes for fingerprints by specialists began with the Metropolitan Police in London with the introduction of civilian fingerprint officers in 1954. Up to that time it was the sole domain of detectives with varying degrees of interest and skill. In 1966 Humberside Police employed the first civilian scenes of crime officers, followed by the Metropolitan Police in 1969. Other police forces in the UK followed suit using a mixture of civilian and police personnel. The term scenes of crime officer or SOCO became synonymous with the role. Other police forces (such as Durham) used the term scientific aids, but soon came in line with the rest of the UK.
The role was seen as one of crime scene examination for a number of years, which belied its full impact within the investigation process. That was not good enough as far as I was concerned because it failed to recognise the integration of science within the whole investigation. Dave Werrett (a pioneer in the introduction of DNA technology into forensic science and who later become head of the UK Forensic Science Service) used the phrase which I always liked. He referred to the ‘continuum’. This aptly describes the seamless process from crime scene to court. Many players take part in the process but it should have one purpose and goal. To me it was always a matter of escalation, from the first patrol officer who attended the crime and realised there was something more than they could handle, to the detective and the specialist crime scene person, to the specialist scientist in a particular evidence type. Each adds his or her own knowledge, training and expertise to the problem until a definitive answer can be found. The crime scene investigator is in real terms a compromise. They are the eyes and ears of the expert scientist in every conceivable field. It isn’t possible or practical to regularly bring every expert to the scene to conduct their own examinations. This is not to say that experts never attend scenes and examine areas specific to their expertise. They do. They are called as part of the escalation process when the scene investigator establishes that the scene is beyond their own skills. As a crime scene investigator I needed to maintain a crust of knowledge of all the forensic science disciplines and be able to handle new ones. This I could do by holding to core principles whilst seeking advice from wherever I could get it. Compromise may be a harsh description of a scene investigator, but that is how the role started out. It understates the investigative role which has added immense value to criminal investigation and has developed now into the management of the scene investigation process.
The standard text Techniques of Crime Scene Investigation, first published in the 1950s, was a bible to me but even it did not demonstrate the application and dynamics of the investigative team and process. This comprehensive textbook fully explores the techniques I would use in crime scene examination, but did not explore the communication and interaction with others that I saw as true investigation. By 1989, when I led the development of the Forensic Science Society diploma, there was no doubt in my mind that we were testing scene investigators and not just scene examiners. So against some resistance (well quite a bit actually, as I will explain later), the Diploma in Crime Scene Investigation was born.
Forensic science is not just about fingerprints and blood, which are often seen as the easy options, giving the highest returns. Any contact trace or residue which can prove a crime has taken place or link an offender should be considered.
So the toolbox of the crime scene investigator is full of technologies and evidence types: paint, glass, shoe marks, tyre marks, bite marks, ear marks, blood, semen, saliva, urine, hairs, fibres, firearms residues, toxicology, poisons, ballistics, pollen, vegetation, fire accelerants, inks, latent marks and impressions, physical and mechanical fit, computers, light sources and many more.
All these technologies are worth nothing without much more important tools. Technologies continue to improve and changes in legislation necessitate finding new ways to enforce our laws and detect when they have been broken. However, the enquiring mind and the ability to listen and question are the most important qualities of an investigator. The answers to questions such as who, where, when and why remain unchanged. When these answers are sought, only then can the quest to methodically search, test, recover, record, review and evaluate evidence begin. The final question is to determine what it all means.