e until dry to prevent
warping and wrinkling. After drying, trim the two enlargements to the
same square size with heavy scissors, a pen knife or scalpel, and
fasten them together, book-fashion, with strips of the photographic
tape used in blocking the negatives. Of course, if charts are large,
20 to 36 inches square, mounting is unnecessary and they will have to
be supported in the courtroom with thumbtacks or metal rings.

Some courts do not permit numbering or lining of the photographs and
the enlargements alone in these cases will have to suffice. If there
is some question about admissibility of the charted enlargements, it
is well to prepare an extra uncharted set.

CHAPTER XVII

_Unidentified Latent Fingerprint File_

From time to time the FBI is requested to conduct surveys and
participate in conferences and in police schools on the problem of
fingerprint identification.

As a result of its observations in the course of these activities it
has been found that many identification bureaus are not fully aware of
the importance which latent finger impressions can have in connection
with the ordinary handling of arrest fingerprint cards.

Many bureaus and departments spend considerable time in developing
latent impressions in a particular case. If no immediate results are
forthcoming, the latent impressions are filed for future reference.

Single fingerprint files have been maintained with success by some
departments. Many others do not attempt to keep a file because of
either limited personnel or lack of funds. In many departments,
however, where such a file is maintained, too often latent impressions
are simply filed with no regard to possible future use. Actually,
these impressions should be treated as evidence directly connecting
the subject with the crime.

Active consideration should be given to the latent impressions until
they are identified or the case has been successfully prosecuted. It
is definitely felt that the following suggested procedure might have
some decided advantages.

It is suggested that in all cases where latent impressions are
developed at the crime scene, or on an object used in connection with
the commission of a crime, the impressions be properly photographed
and lifted. The evidence, where possible and practicable, should be
properly packed, labeled, and stored for future use in court (fig.
430).

Use care in wrapping the evidence to see that the latent impressions
o