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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