Fingerprint Classification and Comparison Methodology
Fingerprint Classification and Comparison Methodology
This domain tests the Henry and NCIC classification systems, pattern interpretation, and the ACE-V comparison method.
Core rules
- Three pattern families: arches (plain, tented), loops (ulnar, radial), and whorls (plain, central pocket, double loop, accidental). Classification depends on ridge count and tracing.
- ACE-V: Analysis assesses clarity, distortion, substrate, and features; Comparison is a side-by-side ridge-by-ridge review; Evaluation yields identification, exclusion, or inconclusive; Verification is an independent second examiner.
- Ridgeology considers level 1 pattern, level 2 minutiae such as ridge endings, bifurcations, dots, and islands, and level 3 pores and edge shape.
- Document the basis for the conclusion; do not use a point count as a substitute for a holistic assessment.
- Note distortion, scarring, and pressure changes because they affect comparison.
Worked example
A latent print from a glass bottle is compared to a known ten-print card. In Analysis, note the loop pattern, a clear delta, and a ridge count of 14; the latent is slightly smudged but has 12 clear minutiae. In Comparison, align the delta and count ridges to confirm the same area; the minutiae configuration matches. Evaluation is identification because the arrangement and relative positions agree and there are no unexplained differences. Verification by a second examiner confirms.
Traps
- Counting points without assessing pattern and clarity.
- Ignoring distortion or scar tissue.
- Comparing a latent to a single known print rather than the full ten-print card.
- Skipping verification.
- Overstating an inconclusive result.