The Science of Fingerprints Part 20

1. The use of poor, thin, or colored ink, resulting in impressions which are too light and faint, or in which the ink has run, obliterating the ridges. The best results will be obtained by using heavy black printer's ink, a paste which should not be thinned before using. This ink will dry quickly and will not blur or smear with handling.

2. Failure to clean thoroughly the inking apparatus and the fingers of foreign substances and perspiration, causing the appearance of false markings and the disappearance of characteristics. Winds.h.i.+eld cleaner, gasoline, benzine, and alcohol are good cleansing agents, but any fluid may be used. In warm weather each finger should be wiped dry of perspiration before printing.

3. Failure to roll the fingers fully from one side to the other and to ink the whole area from tip to below the first fissure. The result of this is that the focal points of the impressions (the deltas or cores) do not appear. The whole finger surface from joint to tip and from side to side should appear.

4. The use of too much ink, obliterating or obscuring the ridges. If printer's ink is used, just a touch of the tube end to the inking plate will suffice for several sets of prints. It should be spread to a thin, even film by rolling.

5. Insufficient ink, resulting in ridges too light and faint to be counted or traced.

6. Allowing the fingers to slip or twist, resulting in smears, blurs, and false-appearing patterns. The fingers should be held lightly without too much pressure. The subject should be warned not to try to help but to remain pa.s.sive.

The ill.u.s.trations numbered 366 through 377 show the results of these faults and show also the same fingers taken in the proper manner.

_Illegible inked prints_

A brief review of the problems of cla.s.sifying and filing a fingerprint card in the FBI will help to clarify the FBI's policy concerning the processing of "bad" inked fingerprints.

The criminal fingerprint file contains the fingerprints of millions of individuals. The complete cla.s.sification formula is used. To obtain it, each inked finger must show all the essential characteristics.

Because of the immense volume of prints it has become necessary to extend the normal cla.s.sification formula.

To ill.u.s.trate this point:

dWdwc xCdwc O 32 W OOO 18 I 32 W III

In order to subdivide the 32 over 32 primary still further, the ridge count of the whorl of the right little finger is used to obtain a final cla.s.sification. The extension above the normal cla.s.sification formula indicates that each whorl is cla.s.sified as to the type; namely, plain whorl (W), double loop (D), central pocket loop (C), and accidental (X). Accordingly, it is not enough for the FBI Identification Division to ascertain the general whorl pattern type, but the deltas and core must show in order to obtain the ridge tracing, the type of whorl, and also, in some instances, the ridge count. The complete WCDX extension is outlined in Chapter VI.

Figures 366 to 377 are some examples of improperly and properly taken inked fingerprints.

An examination of figure 372 shows that it is a whorl. In order to cla.s.sify the ridge tracing accurately, however, so that the fingerprint card can be placed in the correct cla.s.sification, the left delta must show. The approximate ridge tracing for the whorl in figure 372 would be MEETING. An examination of the properly taken fingerprint in figure 373 indicates that the correct ridge tracing is INNER. It follows that the pattern in figure 372 would not have been placed in the proper place in file.

[Ill.u.s.tration: 366. Improper.]

[Ill.u.s.tration: 367. Proper.]

[Ill.u.s.tration: 368. Improper.]

[Ill.u.s.tration: 369. Proper.]

[Ill.u.s.tration: 370. Improper.]

[Ill.u.s.tration: 371. Proper.]

[Ill.u.s.tration: 372. Improper.]

[Ill.u.s.tration: 373. Proper.]

The correct whorl tracing is needed to obtain the complete subsecondary and the major cla.s.sifications.

It may be noted that both deltas are present in figure 374. This would enable the technical expert to ascertain the correct ridge tracing, OUTER. In the core of the whorl, however, there is a heavy amount of ink which makes it impossible to determine the type of whorl with any degree of accuracy. If one were to hazard a guess, it would appear to be a plain whorl. Actually, the correct type of whorl, a double loop, is clearly visible in figure 375.

It can be ascertained that the pattern in figure 376 is a loop, but an accurate ridge count cannot be obtained because the left delta does not appear. The approximate ridge count of this loop is 14 to 16.

This approximation is sufficient for a fingerprint expert to place this loop in the "O" group of any finger of the subsecondary. The correct ridge count of this loop is 19, and it appears in ill.u.s.tration 377. The approximate ridge count is not sufficient to place this print properly in the large files of the FBI because in certain general complete cla.s.sification formulas the accurate ridge count is needed to obtain an extension. These extensions use a smaller grouping of ridge counts to form a valuation table, and in this way, differ from the larger grouping of ridge counts which form the basis of the subsecondary cla.s.sification. These extensions are called the second subsecondary and the special loop extension and are outlined in chapter VI.

[Ill.u.s.tration: 374. Improper.]

[Ill.u.s.tration: 375. Proper.]

[Ill.u.s.tration: 376. Improper.]

[Ill.u.s.tration: 377. Proper.]

There are two additional points which ill.u.s.trate the FBI's need for the delta, ridges, and core to show clearly in loops. The first point is set forth: the ridge count of the loop may be needed to obtain the key cla.s.sification. The key cla.s.sification is an actual ridge count, and no valuation table is used to obtain a subdivision. The key cla.s.sification is used as an integral part of the fingerprint filing system. The second point is as follows: the ridge count may be needed to obtain the final cla.s.sification. The final cla.s.sification is an actual ridge count, and no valuation table is used to obtain a subdivision. The final cla.s.sification is used as an integral part of the fingerprint filing system.

The following are just a few examples to ill.u.s.trate the completeness of the cla.s.sification formula used in the FBI fingerprint file:

12 M 9 R OIO 11

S 1 R IOI

Key Major Primary Secondary Subsecondary Final

6 17 aW IIO 9

1 U OII Key Primary Small letter Subsecondary Final Secondary

8 S 1 Ua II 6 S 1 U III

Key Major Primary Small letter (Subsecondary Final Secondary Extension)

SML (Second SML Subsecondary) 5 0 5 U IOO 14

I 17 U IOO

Key Major Primary Secondary Subsecondary Final

245 (Special Loop 332 Extension) 14 M 1 U IOO 16

S 1 U OII

Key Major Primary Secondary Subsecondary Final

15 I 29 W IOO 19

I 28 W OOI

Key Major Primary Secondary Subsecondary Final

These several examples should help to ill.u.s.trate the FBI's extended cla.s.sification formulas for cla.s.sifying and filing fingerprints. The larger collection of fingerprints must of necessity call for a more detailed a.n.a.lysis of all fingerprint characteristic details. The closer examination to obtain further fingerprint subdivisions is dependent on ten legible inked impressions.