Page 191 - Automated Fingerprint Identification Systems (AFIS)

176 AUTOMATED FINGERPRINT IDENTIFICATION SYSTEMS

fingerprint training, a second from Agency B who does not have that training.
Experience will show that the specialist from Agency A will cull out those images
that have insufficient ridge structure to effect a positive identification. Likewise,
this specialist may see ridge detail not noticed by the untrained eye. What
appears as a smudge may have sufficient detail to make an identification. From
the 100 crime scene prints, the specialist trained in fingerprint identification
will select fewer prints for searching because he or she has discarded those
images not suitable for searching. In this example, the fingerprint-trained spe-
cialist finds 80 latent prints “of value” for searching on the AFIS system. The
specialist without the fingerprint training from Agency B collects every latent
image, regardless of the amount of ridge structure present, intending to allow
the fingerprint technicians at headquarters determine whether the image is “of
value.” Therefore, this technician has selected all 100 images.
These differences in data will affect the final statistics. Agency A, with the
fingerprint-trained evidence technician, has 80 latent prints to search on the
AFIS system, while Agency B has 100. If each agency makes identifications on
the same ten images, the first department will have a fingerprint hit rate of
12.5% (ten identifications divided by 80 latent prints), while the second depart-
ment will have a fingerprint hit rate of 10% (ten identifications divided by 100
latent prints). Is one right and the other wrong? Does it make a difference?

8.5.1.3 What Types of Crimes Usually Have Lifts Collected?
Fingerprints are not lifted from every crime scene. Due to resource limitations
such as staffing not every crime scene that is likely to contain latent prints is
searched by a forensic team. There may be a dollar threshold on stolen prop-
erty that is used to determine if an evidence collection team will be used. Crimes
such as homicide nearly always have technicians present at the crime scene to
collect evidence.

8.5.1.4 Are Elimination Prints Taken?
In addition to the latent prints found at the crime scene, departments may take
elimination prints, which are prints of persons who have a legitimate reason
for being at the crime site that are used to eliminate them as suspects. In the
case of a burglary, elimination prints might be taken of the homeowner,
family members, and other persons who had a legitimate reason for being at
the crime scene, most likely before the time of the crime. Police officials, who
of course are also present at the scene of the crime, usually already have their
fingerprints stored on the AFIS system. As part of a background check, police
applicants are fingerprinted and their finger images are kept on file. The
expertise required of the fingerprint examiner who makes identifications on