Practice

Fingerprint Sciences: Applied Principles and Casework Scenarios

This medium-level mock moves beyond definitions into application — requiring students to interpret development sequences, apply ACE-V methodology to scenarios, understand technique selection logic, and reason about multi-evidence coordination. All thirty questions require understanding of why, not just what. Questions cover: ridge count discrepancy in ACE-V Comparison (not automatic exclusion), sequential processing protocol for paper (ALS → DFO → ninhydrin → PD), banknote development as a complex substrate, double loop whorl classification (two deltas = whorl), ACE-V Analysis stage requirements (latent only + prediction), DFO excitation wavelength (blue-green, 470–505 nm), Small Particle Reagent for wet non-porous surfaces (MoS2 + water), ACE-V identification criteria (sufficient quality + quantity + no unexplained differences), Henry positional values (even fingers = numerator, odd = denominator, each set independently coded 16-8-4-2-1), VMD for plastic bags (most sensitive for polyethylene), ACE-V Comparison discrepancy evaluation (distortion consideration before exclusion), plantar print comparison using ACE-V (equally individualised as fingertips), forensic laser for weak inherent fluorescence, on-body fingerprint challenges (dynamic skin substrate), loop vs whorl vs arch classification (three-part definition with delta criterion), few-minutiae latent prints as more critical in ACE-V, extended Henry Classification system (final + key classification for large collections), fingerprint development on firearms (multiple surface types + curved surfaces + GSR), zinc/cadmium chloride post-ninhydrin enhancement (converts to fluorescent complex), wet glass from river processing (SPR while wet or dry then powder/cyanoacrylate), friction ridge skin individualisation vs fingerprint identification terminology, multi-evidence document with blood and fingerprints (ALS first → biology → fingerprint chemistry), PCAST method-validation vs result-validation critique of ACE-V (blind verification required), ALS with barrier filter for fluorescent powders, blood fingerprint as dual evidence (coordinate fingerprint and DNA sections), distortion definition (deposition factors causing ridge variation without different source), PD as final step in paper protocol (aqueous would destroy amino acid residues if applied earlier), loops and arches as zero in primary classification (binary whorl/non-whorl simplicity), insufficient detail as Analysis stage conclusion (vs inconclusive as Evaluation), and weak ninhydrin development (old/poor-secretor print → zinc chloride enhancement). Themes covered: - ACE-V stages: Analysis requirements, Comparison discrepancy evaluation, Evaluation identification criteria, distinction between unsuitable and inconclusive - PCAST 2016: method-validation vs result-validation critique; blind verification - Development techniques: DFO excitation wavelength, SPR for wet non-porous, post-ninhydrin zinc chloride, PD position in sequence, banknotes, firearms, plastic bags (VMD), wet glass - Henry Classification: positional values (even/odd fingers), double loop whorl (two deltas), loops/arches = zero in primary, extended system - Application scenarios: multi-evidence coordination, blood fingerprints, on-body prints, plantar prints, few-minutiae latent prints - Terminology: distortion definition, friction ridge skin individualisation Each question carries a detailed explanation citing Ashbaugh (1999), Lee and Gaensslen (2012), and the PCAST 2016 report. Allow 15 minutes.