Page 120 - Automated Fingerprint Identification Systems (AFIS)

FROM PRINT TO IDENTIFICATION 105

The complete capture of this information is also extremely important. A nail-
to-nail roll may be the only opportunity to capture image characteristics that
may be used in the future to make a latent print identification. Without a com-
plete nail-to-nail roll, the opportunity for latent print identification diminishes.
AFIS searches depend on the images captured. Most of the work performed
by the AFIS systems can be done by the computer. The minutiae and ridge flow
can be determined by electronic coders, and the electronic matchers can
compare the characteristics of the submitted image with the characteristics of
the images stored in the database. If the score is sufficiently high and other
search parameters match (e.g., the name on fingerprint card matches the name
on the CCH file), the system can declare a “lights out” identification without a
human ever having looked at the images or the candidate list. An increasing
number of AFIS agencies are using the “lights out” procedure, and to do this
they are relying on the score of a fingerprint search that meets or exceeds an
established threshold.
The quality of the images also has a tremendous effect on the likelihood of
making a latent print identification on the subject at a later time. AFIS systems
can store more than 100 individual minutiae points, the ridge flow and other
characteristics. If the subject is fingerprinted with sufficient clarity such that 100
minutiae are captured in a nail-to-nail roll, then the AFIS has almost a com-
plete record of the finger image. If at some time in the future the subject is
fingerprinted again, there is a sufficient amount of information to compare
against, particularly if the subsequent fingerprint capture is also of good quality.
But what if the first capture is only of poor or fair quality?
If the captured image does not contain the minutiae and other characteris-
tics available, the likelihood of making an identification in the future begins to
diminish, particularly in a latent print search. Suppose that instead of 100 minu-
tiae captured in the first printing, only 50 minutiae and image characteristics
were captured, and the captured image is not the complete nail to nail, but just
the upper half of the finger. This partial print image is added to the database.
If a subsequent search of the same subject is made, his or her finger images
would again be captured either on paper or electronically. If this capture is of
fair quality, there would still be enough minutiae to make an identification.
Tenprint searches also generally use two or more fingers, so fair images can
produce an identification. The criminal history is forwarded to the submitting
agency and the criminal history is updated with this new event. The tenprint
identification process is complete. This, however, might not be enough for a
subsequent latent print search.
Suppose the subject was engaged in a criminal activity such as a burglary and
left a latent print at the scene of the crime. If that latent print came from the
portion of the finger that had not been captured on the tenprint record, then