The use of science and scientific methods to detect criminals is not much more that one hundred years old. Police officers and detectives have always used deductive methods to try and isolate the culprit in a crime, but the use of scientific knowledge is relatively recent.
If you want to write in the very popular modern format which has the forensic science aspect as the focus of the story, then you will need to do a lot of research. An excellent reference for this is Crime Scene: the ultimate guide to forensic science by Richard Platt, published by Dorling Kindersley in 2003. For most crime writing, the basic tools familiar to readers are sufficient. But you still need to be accurate in both the science, and what was known at the time of your crime. Here are some basics:
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Fingerprints It was only late in the nineteenth century that it was realised that fingerprints alone were a form of identification. The pattern of grooves on each individual's fingerprints are quite unique. No two people have the same patterns - not even identical twins. This scientific principle was able to be used to identify individuals who had been at particular places. It was discovered that by using a fine dust, fingerprints could be made to show up on weapons, furniture, or other hard surfaces. Photographs could then be taken and compared with inked fingerprints. DNA identification, which is a form of genetic fingerprinting, is now used. It takes longer, but can identify people from a small amount of their skin, blood, hair or anything else which contains their unique DNA. |
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Blood Each individual has a particular blood group depending on the antigens found in their blood cells. There are four main groups - O, A, B and AB. Then there is the Rh system - the positive and negative antigens. So someone might be B-positive or B-negative. Matching a person to a blood types cannot identity them as having been involved in the crime, because so many people have the same blood group. It can certainly eliminate them if their blood group doesn't match. DNA profiling is more sophisticated, more expensive and takes longer, but it can identify an individual. The way blood is left at the scene of the crime is an important part of forensic science. It can show whether it flowed or was spattered, or fell from a height. It can give angles of attack. Old stains can be identified as well as fresh ones. If you are writing historical crime, be careful of the timing. Human blood could be distinguished from animal blood as a result of the work of German biologist, Paul Uhlenhuth in 1900. Digitalised DNA profiling resulted from the work of Professor Alec Jeffreys in England in the early 1990s. |
Hair Hair analysis can point to what animal has left the hair. Further than that, human hair can give clues as to the age, gender and race. Hair will outlast many other clues, which is very useful should you wish your detective to deal with a very old crime. Hair retains traces of poisons or drugs, so a great deal can be told about the history of a drug user or someone who has been poisoned. DNA testing can be done on a single hair! |
 Cat hair (left) and human hair (right) |
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Poisons There are a lot of myths and dated information about poisons, so be careful if you are going to use a poison in your plot. It is no longer possible to commit suicide or kill someone with an overdose of sleeping tablets. Drug companies have ensured that is the case. Police can detect a whole range of poisons in dead bodies. Poisoning may be deliberate or accidental. A knowledge of chemicals, their source and the way they act, is vital to forensic science. Choose your poison wisely and do the research to know exactly how it would be obtained in the era of your story. |
Documents Since a significant proportion of crime relates to the theft of money or fraud, the introduction of evidence taken from documents can be an intriguing touch to a crime story - they are so familiar to all of us. Handwriting is an obvious area to investigate. Types of handwriting and signatures have been extensively studied for clues as to the profile of the writer, but are mostly used to match with other samples of a suspect's writing. The source of the paper is also a clue. It is possible to use infrared technology to detect documents which have been changed, such as a falsified medical record to make false insurance claims. Even burnt documents can sometimes be read. Then there are the contents of the message! |
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Arson is the deliberate burning of property for criminal reasons such as:
* defrauding an insurance company Pyromania is a mental illness, which leads to a psychotic need to light fires. A pyromaniac may be the cause of a spate of fires in an area. . |
These are just few examples to consider using in your story to give it an authentic feel. Depending on your crime and setting, you will need to research just what you need to know.
Decide what forensic evidence might be used in your crime and find out what you need to know about it.
Do the research and check the details so your reference to the forensic procedure is accurate. Even if it is only a sentence, a good story is ruined for a reader if they know something to be factually wrong.
