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Articles from The Science Of Fingerprints

Classification Of Bandaged Or Imprinted Fingers

Fingerprinting Equipment

General Photography

Technical Consideration

The Classification Formula

Latent Impressions

The Identification Division Of The Fbi

Water-soaked Fingers

Jacket Folder File

Illegible Inked Prints


When searching a print through the fingerprint files in order to
establish an identification, it should be remembered that the
fingerprint cards are filed in such a way that all those prints having
the same classification are together. Thus, the print being searched
is compared only with the groups having a comparable classification,
rather than with the whole file.

After locating the proper group classification, the searcher should
fix in his mind the one or two most outstanding characteristics of the
patterns of the current print and look for them among the prints in
file. If a print is found which has a characteristic resembling one
upon the current print, the two prints should be examined closely to
determine if identical. To avoid making an erroneous identification,
the searcher should be exceedingly careful to ascertain that the
prints being compared are identical in all respects before identifying
one against the other.

To establish identity, it is necessary to locate several points of
identity among the characteristics of the prints. The number of
identical characteristics is left to the discretion of the individual
but he should be absolutely certain that the prints are identical
before treating them as such. Characteristics need not appear within
the pattern area, since any ridge formation is acceptable. Quite often
excellent ridge detail appears in the second joint of the finger. The
characteristics used to establish an identification are shown in
figure 102.

The final and the key may be considered control figures for searching
prints. They limit the number of prints it is necessary to search in a
group to those prints having finals and keys closely related to the
final and key of the print being searched.

Due to the possibility of visual misinterpretation, distortion by
pressure, or poor condition of the ridge detail of the prints in file,
it is advisable to allow a margin for such discrepancies. Except in
cases where the ridge count of the final and/or key is questionable on
the print being searched, the following procedure is used:

Of the prints within any group classification, only those prints are
examined which have a final within 2 ridge counts on each side of the
final of the print being searched. For example, if the print to be
searched has a final of 17, all prints bearing a final 15 through 19
will be compared with it.

Within the final of any group classification, only those prints are
examined which have a key within 2 ridge counts on each side of the
key of the print being searched. For example, if the print to be
searched has a key of 20, all prints bearing a key of 18 through 22
will be compared with it.

In figure 352, it will be noted that there are 17 ridge counts
appearing in the right little finger and this number is used as the
final. It will also be noted that there is a loop of 24 ridge counts
in the right thumb and this number is used as the key inasmuch as it
is the first loop. In this example, the print is searched in the group
classification which has finals ranging from 15 through 19. Within
this group of finals the prints which have keys ranging from 22
through 26 are examined.

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Previous: Filing Sequence

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