reverse-color negative should be prepared and
blocked in order that both prints may appear as black ridges on light
backgrounds. This is done by placing the original negative adjacent to
a new sheet of film and exposing it. The resultant negative contains
the same image as the original except that the color of the image has
been reversed.

If the negative is a photograph of an opaque lift, the print appears
in reverse position; that is, as a mirror image, and the negative will
accordingly have to be blocked from the dull or emulsion side in order
for it to appear in a position comparable to that of the inked print.

Failure to present the prints in question in the same color and
position may possibly confuse the observer and nullify the purpose for
which the chart is made.

The degree of enlargement is not important in itself, so long as the
ridges of the latent print are readily distinguishable by the eye. Ten
diameters have been found adequate, although any enlargement from 5 to
30 will serve. It should be remembered, however, that small
enlargements are difficult to see a few feet away and that large ones
lose some of the contrast between ridges and background. A white
border of at least 1-1/2 inches or a width equal to about one-third
the enlarged area should be left for charting purposes.

Any chart prepared must be technically correct; that is, the
corresponding ridge characteristics in the two prints must be
similarly numbered and indicated.

Several ways of pointing out the similar ridge formations have been
observed, but the one which appears soundest is also simplest and
consists of merely marking the characteristics with lines and numbers.

All of the ridge characteristics in the prints need not be charted.
Twelve characteristics are ample to illustrate an identification, but
it is neither claimed nor implied that this number is required.

All fingerprint identifications are made by observing that two
impressions have ridge characteristics of similar shapes which occupy
the same relative positions in the patterns.

Methods involving superimposition of the prints are not recommended
because such a procedure is possible only in a very few instances, due
to the distortion of ridges in most prints through pressure and
twisting. Such a procedure is not necessarily a test of identity.

Likewise, presenting charts with the shapes of the characteristics
drawn in the margin is not recommended. Individual ri