Page 127 - Automated Fingerprint Identification Systems (AFIS)

112 AUTOMATED FINGERPRINT IDENTIFICATION SYSTEMS

Table 5.1
Tenprint Searches—Pre- and Post-AFIS

Process Pre-AFIS Post-AFIS

Acquisition of fingerprints Ink + roll Ink + roll, livescan
Transmission of fingerprint images Mail, courier, or facsimile Mail, courier, livescan, or group IV facsimile
Transmission of fingerprint data Mail, courier, facsimile, or Mail, courier, facsimile, livescan, or
electronic interface electronic interface
Storage of fingerprint images Inked images Inked images captured on optical disks
Search processing Name search followed by Name and fingerprint search using
manual counting of ridges computerized matching and high-
with magnifying glass resolution monitors
Verification by Examiner based upon manual Examiner using high-resolution monitors
examination with glass

5.4 TYPES OF AFIS SEARCHES

5.4.1 TENPRINT TO TENPRINT (TP/TP) SEARCHES
In pre-AFIS days, a clerk had to retrieve a tenprint card from the master fin-
gerprint file, present it to the examiner for comparison, then return the card
to the file. If another examiner needed that card, he or she had to either wait
for the card to be returned to the file or retrieve another tenprint card on the
same person from the jacket. Today, the candidate image is presented for side-
by-side comparison with the subject image on high-quality computer monitors,
and the examiner uses electronic tools to filter image data. Minutiae can be
hidden, portions of the image magnified, and locked cursors can move across
the two images simultaneously. See Table 5.1 for a comparison of pre- and post-
AFIS tenprint search processes.
In tenprint searches, the use of two or possibly four finger images adds to
the likelihood of making an identification. If two candidates appear, and their
scores are high and similar, it may be due to a consolidation. 3
The candidates produced in a TP/TP search are displayed on a candidate
list in rank order. The tenprint examiner compares each AFIS-produced can-
didate against the subject image. While the matcher determines the relative
placement of minutiae and patterns on the two images, the examiner can also
check items such as ridge flow, core, and delta. This is the tenprint verification
process.
Many AFIS systems require a duplication of this process, known as validation.
In validation, a second examiner independently reviews the candidates, noting

3 A consolidation consists of finger images from the same persons that were assigned different SID
numbers. Not everyone is completely forthright when they are fingerprinted.