Page 124 - Automated Fingerprint Identification Systems (AFIS)

FROM PRINT TO IDENTIFICATION 109

CCH
Store
and Name
Forward Search
Enter
Booking
Data
Candidates
Fingerprint Generated
Images
NO OK?

YES
Enter Patterns
Center Image
Check Rotation
Extract Minutiae

Fingerprint
Minutiae
Search
Launched

Fingerprint
Candidates
and
Name Search
Candidates
Combined

At the same time, the AFIS system can check the quality of the finger images. Figure 5.11
If the images do not meet the standards, e.g., are unusable, they are sent to a Overview of Name and
quality control unit for review. If it is confirmed that the images are not usable Minutiae Search
(e.g., blurred, transmission error), the booking agency may be asked to re-roll
the subject. While this is usually possible with livescan-produced records
because of the speed with which booking and review can be done, it is less likely
to occur when the records arrive via card scan. For records that arrived by mail,
the chances of a re-roll are almost nil.
If the quality of the images is acceptable, they are checked for patterns
and centered, and it is ensured that the rotation is true (i.e., that the tip of
the finger appears at the top). When these checks are complete, the coder
extracts minutiae from the images and a tenprint to tenprint (TP/TP) search
is launched. Tenprint matchers search those records that meet the pattern
classification of the ten finger images, and then match the minutiae for two
or more fingers. From this search a candidate list is produced. AFIS then
combines the candidate list from the minutiae search with the list of candidates
produced by searching the MNI and compares candidates (see Fig. 5.12).