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Articles from The Science Of Fingerprints

Double Loop

Deceased Infants

Record Of Additional Arrest


Latent Impressions


Ridge Counting

Chemical Development Of Latent Impressions

Desiccation And Charring

Central Pocket Loop

Illegible Inked Prints

A brief review of the problems of classifying 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 classification 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 classification formula.

To illustrate this point:

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 classification. The extension above the normal classification
formula indicates that each whorl is classified 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
classify the ridge tracing accurately, however, so that the
fingerprint card can be placed in the correct classification, 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.

[Illustration: 366. Improper.]

[Illustration: 367. Proper.]

[Illustration: 368. Improper.]

[Illustration: 369. Proper.]

[Illustration: 370. Improper.]

[Illustration: 371. Proper.]

[Illustration: 372. Improper.]

[Illustration: 373. Proper.]

The correct whorl tracing is needed to obtain the complete
subsecondary and the major classifications.

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 illustration
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 classification 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 classification. These extensions are called the second
subsecondary and the special loop extension and are outlined in
chapter VI.

[Illustration: 374. Improper.]

[Illustration: 375. Proper.]

[Illustration: 376. Improper.]

[Illustration: 377. Proper.]

There are two additional points which illustrate 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 classification. The key classification is an actual ridge count,
and no valuation table is used to obtain a subdivision. The key
classification 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 classification. The final classification is an
actual ridge count, and no valuation table is used to obtain a
subdivision. The final classification is used as an integral part of
the fingerprint filing system.

The following are just a few examples to illustrate the completeness
of the classification formula used in the FBI fingerprint file:

12 M 9 R OIO 11


Key Major Primary Secondary Subsecondary Final

6 17 aW IIO 9

Key Primary Small letter Subsecondary Final

8 S 1 Ua II 6

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


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 illustrate the FBI's extended
classification formulas for classifying and filing fingerprints. The
larger collection of fingerprints must of necessity call for a more
detailed analysis of all fingerprint characteristic details. The
closer examination to obtain further fingerprint subdivisions is
dependent on ten legible inked impressions.

The identification officer will understand the problems of accurately
classifying and filing fingerprint cards. He knows there is little
value in placing a fingerprint card in the FBI's files with only an
approximate or an inaccurate classification.

Every fingerprint card filed in the FBI's file is of value to the
particular law enforcement agency which forwarded it, as well as to
all other law enforcement agencies which rely on its being correctly
classified and filed.

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