The Science of Fingerprints, United States. Federal Bureau of Investigation [good books to read in english TXT] 📗

● Those who have died recently, in which cases the task is relatively simple.

● Those dead for a longer period, in which cases difficulty is experienced due to pronounced stiffening of the fingers, the early stages of decomposition, or both.

● Those cases in which extreme difficulty is encountered because of maceration, desiccation, or advanced decay of the skin.

These problems will be considered separately.

1. Fingerprinting the Newly Dead.

When the fingers are flexible it is often possible to secure inked fingerprint impressions of a deceased person through the regular inking process on a standard fingerprint card. Experience has proved that this task can be made easier if the deceased is laid face down and palms down on a table (fig. 388).

Fig. 388

[Fig. 388]

In all cases where inked impressions are to be made, care should be exercised to see that the fingers are clean and dry before inking. If necessary, wash the digits with soap and water and dry thoroughly.

In the event difficulty is encountered in trying to procure fingerprints by the regular method, it may prove more convenient to cut the 10 "squares" numbered for the rolled impressions from a fingerprint card. After the finger is inked, the square is rolled around the finger without letting it slip. Extreme caution should be exercised to see that each square bears the correct fingerprint impression. After all the inked impressions are properly taken, the ten squares bearing the impressions are pasted or stapled to a standard fingerprint card in their proper positions, i.e., right thumb, right index, right middle, etc. Whenever possible the "plain" or "simultaneous" impressions should also be taken.

In some cases it will be found necessary to obtain or improvise a tool similar to a broad-bladed putty knife or spatula to be used as an inking instrument. The ink is rolled evenly and thinly on the knife or spatula and applied to the finger by passing the inked knife or spatula around it. The tool, of course, replaces the usual glass inking slab or plate, the use of which is extremely difficult or awkward when printing a deceased person.

2. Fingerprinting the Dead, Where Stiffening of the Fingers and/or Early Decomposition Are Present.

This second group consists of cases in which the hands of the deceased are clenched, or the finger tips are wrinkled, or decomposition has begun, and/or where there are combinations of these three conditions. Cases of this sort may necessitate cutting off the skin. Legal authority is necessary before cutting a corpse. Such authority may be granted by state law or by an official having authority to grant such a right.

In cases where rigor mortis (stiffening of the muscles) has set in and the fingers are tightly clenched, the fingers may be forcibly straightened by "breaking the rigor." This is done by holding the hand of the deceased person firmly with one hand, grasping the finger to be straightened with the four fingers of the other hand and placing the thumb, which is used as a lever, on the knuckle of the finger and forcing it straight (fig. 389). The inking tool and "squares," as previously explained, are then used to secure the fingerprint.

Fig. 389

[Fig. 389]

In the event the rigor cannot be completely overcome, it will be most helpful to improvise or secure a spoon-shaped tool for holding the cut squares or cut strips while printing the fingers, similar to the tool mentioned briefly in the discussion of crippled fingers. This tool, somewhat resembling a gouge without the sharp edge, should have a handle, a concave end, and a frame or clamp to hold the cardboard squares or strips. In Figure 390, one type of tool is illustrated. This tool eliminates the necessity of rolling the deceased's finger, since the "square" assumes the concave shape of the tool, and the gentle pressure applied to the inked finger when it is brought in contact with the square results in a "rolled" impression without actually rolling the finger.

Fig. 390

[Fig. 390]

Another problem encountered in this second group includes cases in which the tips of the fingers are fairly pliable and intact, yet due to the presence of wrinkles in the skin, complete impressions cannot be obtained. This condition can be corrected by the injection of a tissue builder, procurable from a dealer in undertaker's supplies. If this is not available, glycerin or water may be used.

The method is simple. Injection of the tissue builder, glycerin, or water, is accomplished by the use of a hypodermic syringe. The hypodermic needle is injected at the joint of the finger up into the tip of the finger, care being used to keep the needle below the skin surface (fig. 391). The solution is injected until the finger "bulbs" are rounded out, after which they are inked and printed.

Fig. 391

[Fig. 391]

Occasionally, in stubborn cases, entry of the needle at the joint and injection of the fluid will not completely fill the finger bulb. It may be necessary, therefore, to inject the fluid at other points of the finger such as the extreme tip or sides, until suitable results are achieved (fig. 392). The tissue builder has a distinct advantage over glycerin or water, inasmuch as the builder hardens after a short time and is not lost, whereas glycerin and water sometimes seep out when pressure is applied in printing. To offset seepage at the point where the hypodermic needle is injected, whenever possible, tie a piece of string tightly around the finger just above the point of entry of the needle.

Fig. 392

[Fig. 392]

When the tissue builder is purchased, a solvent for cleaning the hypodermic syringe and needle should be acquired, inasmuch as the builder will harden in the syringe and needle.

Those cases in which decomposition in its early stage is present belong in this group also. Frequently, the outer layer of skin has begun to peel from the fingers. A careful examination should be made to determine if the peeling skin is intact or if a part of it has been lost. If the skin is in one piece, an effort should be made to secure prints just as though it were attached normally to the finger. Or, if it is deemed advisable, the skin may be peeled off in one piece, placed over the finger of the operator, and inked and printed as though it were his own finger.

Occasionally the first layer of skin is missing. There remains the dermis or second layer of skin which is also of value for identification purposes. This second layer would be dealt with as though it were the outside skin, using the techniques described above. The ridge detail of the second layer of skin is less pronounced than that of the outer skin, however, and more attention and care are needed in order to obtain suitable impressions.

So far this discussion has dealt with the taking of impressions of fingers when the flesh is fairly firm and the ridge detail intact. A different problem arises when the fingers are in various stages of decay. The techniques of treating the fingers in such cases vary greatly, depending upon the condition of the fingers with respect to decomposition, desiccation, or maceration.

3. Fingerprinting the Dead in Difficult Cases.

In cases involving badly decomposed bodies the first thing to do is to examine the fingers to see if all are present. If they are not, an effort should be made to determine whether the missing finger or fingers or even a hand was amputated during the person's lifetime, or whether the loss was due to other causes such as destruction by animal or marine life. Deductions from this examination should be noted on the fingerprint record. This point is made in view of the fact that in the fingerprint files of the FBI and some police departments, the fingerprint cards reflecting amputations are filed separately. Noting amputations may lessen to a great extent a search through the fingerprint files.

In making the initial examination, attention should be given to the removal of dirt, silt, grease and other foreign matter from the fingers. Soap and water are good cleansing agents. So is xylene, a chemical which will readily clean grease and fatty matter from the fingers. Good results can be achieved by utilizing a child's soft-bristled toothbrush in cases where the skin is fairly firm. The brushing should be done lightly and the strokes should follow the ridge design in order to clean not only the ridges but the depressions as well. In the event that the skin is not firm enough to use the toothbrush, a cotton swab may be used. The fingers should be wiped very lightly with either soap and water or xylene, always following the ridge contours.

At this point the fingers are again examined to determine the condition they are in, based upon the circumstances in which the body was found. Study and actual experience have shown that there are three general types of conditions to be considered: Decomposition or putrefaction, prevalent in bodies found in brush or buried in earth; desiccation or mummification (that is, dried out), noted in bodies which have been found in the open (ridge detail not in contact with the ground) in dry protected places, or bodies subjected to severe heat; and the group involving maceration (water soaking), which ordinarily results from being immersed in water.

The degree of decomposition, desiccation, or maceration varies from a comparatively early stage to an extremely advanced stage. Accordingly, each case must be considered individually. For example, what is done successfully in one case of desiccation may not show favorable results in another. Hence, the techniques outlined below point out generally what can be done, and has been done, with success.

When a body is found, the hands usually will be tightly clenched. The first problem will be to straighten the fingers. If rigor mortis has set in and an effort to straighten the fingers as previously explained fails, the difficulty can be overcome easily. Using a scalpel, make a deep cut at the second joint on the inner side of each of the four fingers. They can now be straightened with the application of force (fig. 393). The thumb, if it is cramped or bent, can generally be straightened by making a deep cut between the thumb and the index finger. These incisions are made for the obvious purpose of examining the fingers to determine if there is any ridge detail. Before this fact can be definitely ascertained it may be necessary to cleanse the pattern areas with soap and water or xylene, as previously explained.

Fig. 393

[Fig. 393]

If the case is one involving decomposition, the operator is confronted with the problem of dealing with flesh which is rotted or putrefied. The flesh may be soft or flabby and very fragile. If this is so, an examination is made of the finger tips to see if the outer skin is present. If the outer skin is present and intact, it may be possible, using extreme care, to ink and print in the regular manner. Sometimes, the outer skin, although present, will be too soft and fragile to ink and roll in the regular way. In such cases, when the ridge detail is discernible, the skin, if it is easily removed from the finger, or the finger itself may be cut off at the second joint and placed in a 10- to 15-percent solution of formaldehyde for approximately an hour to harden it.