The Science of Fingerprints: Classification and UsesUnited States. Federal Bureau of Investigation
Science
The Science of Fingerprints: Classification and Uses
United States. Federal Bureau of Investigation
Fingerprints
The complete process may take from several hours to as much as 10 days
to secure suitable results. If the final results of the above
procedure are satisfactory with the one finger being tested, the
remaining fingers are given the same treatment. Care must be taken to
identify each finger properly as to right index, right middle, etc.,
to avoid any mixup.
In the event that the reaction of the solution on the first finger
treated is not satisfactory and the operator feels that it would be
futile to continue the process, the finger should be removed from the
solution immediately, washed carefully in water, and placed in
formaldehyde to harden sufficiently for it to be handled without
causing injury to the ridges. The pattern area is cut off in such a
manner that sufficient surrounding surface permits the skin to be
trimmed. Then from the cut side the skin is carefully scraped and cut
to remove the excess flesh. While the cutting and scraping are being
done, from time to time the skin should be soaked in xylene and
massaged for purposes of softening to remove wrinkles. When the skin
is thin enough and sufficiently pliable, the operator places the skin
on his own finger, inks and prints it in the usual manner.
If the results are satisfactory, the same procedure is followed with
the remaining fingers. In the event the resultant inked prints are not
suitable, the skin should be scraped until it is sufficiently thin to
be flattened between two pieces of glass and photographed.
Here again it is pointed out that should there be a poor contrast
between the ridges and furrows when using direct lighting, the skin is
scraped as thin as possible without tearing and it is then
photographed by transmitted light.
There are also included, as cases of desiccation, bodies which have
been burned or subjected to severe heat. Often there are cases where
the skin has become loose but is hard and crisp, or where the finger
has been severely burned and is reduced almost to carbon, yet is firm.
In these instances the ridge detail usually has not been destroyed.
When a body which has been severely burned is located, the problems of
identification should be anticipated. Accordingly, before the body is
removed, a careful examination of the fingers should be made in order
to determine if the removal would, in any way, cause damage to the
fingers. Should it be felt that because of the condition of the body
removal would cause injury to the ridge detail, securing of
fingerprints at the scene, or possibly the cutting off of the hands or
fingers to avoid destruction of the skin, should be considered. An
examination of the fingers may disclose that the outer skin is
hardened and is partially loosened from the flesh. It is sometimes
possible, by twisting back and forth, to remove this outer skin
intact. If this is done, the operator may place the skin on his own
finger, ink and print in the usual way.
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