Articles from The Science Of Fingerprints
Jacket Folder File
Chemical Development Of Latent Impressions
Desiccation And Charring
The problem confronting the fingerprint examiner in treating fingers
which are desiccated or dried and shriveled is that of distending and
softening the skin. Desiccated fingers are generally found to have the
outer layer of skin intact and the ridge detail fairly clear. However,
due to the shrinking, numerous wrinkles will be present, and as the
drying process continues the skin and flesh harden until the fingers
become almost as hard as stone.
It is sometimes possible to distend or swell the flesh by utilizing a
1- to 3-percent solution of sodium hydroxide or potassium hydroxide,
sometimes referred to as caustic potash. As a matter of caution, this
process should be tried with one finger before using it for the
remaining fingers. This point of caution is made because of the
reaction of the potassium or sodium hydroxide, which is actually one
of destruction. While absorption and swelling of the flesh occur, the
disintegrating action of the fluid may result in total destruction of
The finger to be distended is cut from the hand at the second joint
and placed in the hydroxide. When it has resumed its normal size by
the absorption of the solution, it is inked and printed. There is no
set time for this process. The procedure may require a few hours or as
much as several days until suitable results are obtained.
After the finger has been in the solution for about 30 minutes, it
should be removed and examined in order to note the extent of the
swelling and the reaction of the flesh to the solution. If no material
change is noted, the finger is returned to the solution. A close watch
is maintained and the finger is examined from time to time.
The solution may cause thin layers of skin to peel from the finger.
Should this occur, the loose skin is carefully scraped off and the
finger rinsed in water for a few minutes. It is then returned to the
hydroxide for continuation of the process.
If, during the course of an inspection, it is seen that the flesh is
becoming too soft, the finger should be placed in a 1- to 3-percent
solution of formaldehyde or alcohol for several minutes in order to
If, after several hours in the hydroxide, the finger has not reached
its normal size, it should be placed in water for an hour or two. This
has a tendency to hasten the swelling. When the finger is removed, it
will be noted that a film has coated the surface. This coating is
carefully scraped off and the finger is replaced in the hydroxide
solution for an hour or so, again scraped if coated, soaked in clean
water, etc. This process of alternating from solution to water,
scraping, and replacing in hydroxide is continued until desirable
results are obtained. The finger is then inked and printed.
The above process will so saturate the finger with solution that it
may be too wet to print properly. Accordingly, the finger may be
dipped into acetone for several seconds, removed, and be permitted to
dry, after which it is inked and printed.
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.
If the skin is intact on the finger and is not wrinkled, of course
there is no problem and the usual method is employed to secure
Should wrinkles be present and the skin pliable, tissue builder is
injected into the bulbs, which are then inked and printed.
In the event the wrinkles cannot be removed in this fashion, the
pattern area is cut off and the excess flesh scraped out as before.
While the scraping and cutting are being accomplished, the skin should
be soaked and massaged in xylene to soften. The skin is then placed on
the operator's finger, inked and printed. Should prints made in this
manner be unsatisfactory, the next recourse is photography.
In some instances the fingers of burned bodies will be charred. Such
cases require very careful handling as there is a probability of
destroying or disturbing the ridge detail through mistreatment. In
these instances the procedure is determined by the degree of charring.
In extreme cases the only method of recording is by photographing,
using side lighting to secure the proper contrast of ridges and
depressions. Obviously, no attempt should be made to ink and roll as
the pressure necessary to secure the prints would cause the skin to
In instances where the charring has not reached the extreme stage the
procedures previously set forth should be applied; that is, treatment
of the skin by cleaning, softening, inking and printing, or, finally,
by photographing (fig. 400).
[Illustration: 400. Photograph of charts used in actual case to
establish the identity of a charred body, victim of murder. Chart A
shows skin removed from one of the fingers treated and photographed.
Chart B shows an inked impression of the same finger during victim's
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