Page 115 - Automated Fingerprint Identification Systems (AFIS)

100 AUTOMATED FINGERPRINT IDENTIFICATION SYSTEMS

of the card absorbed the ink to maximize the quality of the print, the paper
stock had to meet composition specifications. It had to be sufficiently strong to
withstand numerous handlings by fingerprint examiners, fingerprint clerks,
and indefinite file storage.
While the boxes in the first two rows of the fingerprint card contained the
individual nail-to-nail rolled finger images, the four boxes in the lower portion
of the card contained impressions of the fingers, which were referred to as flat,
plain, or slapped impressions. The images in these boxes were captured by
placing a group of four fingers onto the inked platen without any rolling, then
pressing them onto the fingerprint card. After four fingers of both hands were
captured, the thumbs were captured.
The large box on the lower left portion of the card shown in Figure 5.7 con-
tains the plain impressions of fingers 7 through 10, which are the index finger
through the little finger of the left hand. The next box contains the plain
impression of finger 6, the left thumb. Moving on, the next box contains the
image of the right thumb, finger 1, followed by the images of the remaining
four fingers of the right hand, i.e., fingers 2 through 5. Look at the card and
compare the images. Why are there two sets of images of the same two hands?
What is different about the images? What is the same? Look closely.
One difference is that the images of the individual fingers are larger than
those of the plain impressions. This is because the fingerprint technician taking
the prints was attempting to capture as much finger detail as possible. The nail-
to-nail roll captures the most information by including all the ridges, bifurca-
tions, and minutiae from one edge of the fingernail to the other, and from the
tip of the finger to the crease. The nail-to-nail roll also captures more minutiae
at the very tip of the finger than does the plain impression. While the minu-
tiae captured by the plain impressions are sufficient for tenprint identification
purposes, latent print examiners needed as many minutiae as possible to search
against. In many instances of car theft, for example, a latent impression from
only a finger tip is found on the interior rear view mirror. The plain impres-
sion may contain more information below the first joint of the finger, but this
was not typically used in tenprint identification and was not often found in
latent prints.
The two sets of images were important for several reasons. The primary
reason was so that a technician could quickly identify any finger sequence error,
i.e., any finger that was rolled out of order and entered into the wrong box.
If the image for finger 2 (right index) appeared in the box for finger 3
(right middle), it could result in a missed identification. Other mistakes were
possible. Occasionally the finger images of one hand were entered into the
boxes for the other hand, or the five fingers of one hand were erroneously
entered twice and the fingers of the other hand were not rolled. Since the plain