Not only do each and every one of us have very individual traits and looks but we have one thing that makes us completely unique and cannot be altered: these are our fingerprints.
Fingerprints – and their individuality – are one of the most important pieces of evidence that can be presented in the prosecuting of any crime.
Back in 1892 Francis Galton established a classification system for fingerprints working on the old principle of an Indian magistrate who made people sign contracts with their fingerprints. This was considered to be the most personal way of signing contracts and through time he noticed that each fingerprint was different.
Fingerprints identified at crime scenes fall into three categories:
Patent fingerprints are those that are clearly visible to the naked eye and are normally made because the individual has had their fingers in some sort of liquid or powder. Mostly this would be blood, ink, oil or the likes and the fingerprint is clearly visible and a close up photograph is often all that is necessary to record it.
Latent fingerprints are prints that are not visible to the naked eye but are visible under certain conditions; they can be made visible – or certainly more identifiable – by introducing them to a powder or chemical agent.
Impressed prints are those that have been made in soft material or tissue by pressing down with the finger or hand. These prints can be photographed or in certain circumstances moulds made if they are very fragile.
It is important to remember also that fingerprint evidence is normally very reliable. The chances of any two individuals sharing the same fingerprints are roughly one in sixty four billion and therefore the presentation of fingerprints at a scene or location where they would not normally be is a clear indicator that perhaps not all is what it seems.
Fingerprints are made up of a series of whorls, loops, ridges and arch formations but also so are the palms of the hands. Palm prints are also highly important in the compiling of evidence.
It is also possible to achieve accurate fingerprint identification from partial prints; this is a system that has evolved in the last decade and is a computerised system that measures certain points of a fingerprint and attempts to match it against other fingerprints in the system. A high percentage of accuracy can lead to a positive identification.
Collecting Fingerprint Evidence
Given the fragility of fingerprints on certain surfaces it is necessary to use specific techniques to capture them; these include gently brushing over the prints with a magnesium powder and/or cyanocrylic chemical (the likes of which can be found in household superglue). Ultra violet light is also often used for the identification of fingerprints on surfaces where they would not normally be easily visible.
Fingerprints are not only photographed and but are also made on card by impressing the individual fingers onto ink. They are also used for the identification of the deceased as well when normal methods of visual identification are not possible.
It is worth noting also that although DNA samples cannot be held after the completion of a police investigation – unless the suspect is found guilty of a crime; fingerprint information can be kept on file.