The conventional method for treating fingerprints is to dust them with a fine
powder and then dye for observation. This increases the contrast and helps in
examining the fine structures of the print. However, this method also destroys
the traces of chemicals excreted by the skin that could be important evidence.
British criminologists have now developed a new process for this analysis –
and can even determine e.g. whether the suspect is a smoker or a vegetarian.
In their tests, the detectives used prints taken from door knobs, cup handles,
glass plates and even a computer screen. They pressed gelatine film – routinely
used to make impressions of footprints at the scene of a crime – onto these.
Then they were analyzed using an infrared spectrophotometer that measures how
much light has been absorbed by a specific substance and, in this way, were able
to determine the chemical composition.
The sort of substances left with a fingerprint are the fatt y acids of skin exudate
and components of sweat, tobacco and certain foodstuffs. Thus, by producing such
a precise chemical profile from the fingerprint, it can be established e.g. whether
the suspect is a smoker or a vegetarian or which substances such as drugs have been
ingested shortly before.
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This new method enables valuable additional information on the suspect to be
obtained. Furthermore, the original fingerprint remains intact for use in other
tests.
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