IAI CLPE cheat sheet

ACE-V is the documented comparison method: Analysis, Comparison, Evaluation, Verification; each stage is recorded before the next begins.

Analysis establishes the features of the latent (clarity, distortion, matrix, substrate, development technique) and the features of the known print independently.

Comparison is a side-by-side assessment of corresponding features in sequence, not a global visual impression; the examiner documents what was compared.

Evaluation yields one of three conclusions: identification (individualization), exclusion, or inconclusive; no probability or 'possible match' conclusion is permitted.

Individualization requires sufficient quantity and quality of corresponding ridge features in agreement, with no unexplained dissimilarities.

Level 1 detail = ridge flow and pattern type; Level 2 = ridge path, bifurcations, endings, and their spatial relationships; Level 3 = pores, edge shape, and ridge width.

Verification is an independent re-examination by another qualified examiner who reaches the same conclusion; it is not a review of the first examiner's notes for agreement.

Exclusion requires an area of the latent that is clear and undistorted enough to show a true discrepancy in ridge path or feature relationship.

Inconclusive applies when the latent lacks sufficient quality or quantity for either identification or exclusion; it is a valid, reportable outcome.

Development sequence for porous items: visual examination, then amino acid reagents (ninhydrin, DFO, 1,2-indanedione), then physical developers (PD, oil red O) for lipids.

Ninhydrin reacts with amino acids and is developed with heat and humidity (roughly 80 °C and 65% RH); it yields Ruhemann's purple and can overdevelop.

DFO and 1,2-indanedione are fluorogenic amino acid reagents read under laser/ALS with filters; 1,2-indanedione generally gives stronger luminescence than DFO.

Physical developer works on porous surfaces after amino acid reagents and detects lipid/water-insoluble components; it is incompatible with prior wetting by aqueous reagents.

Cyanoacrylate fuming polymerizes on non-porous surfaces; acceleration is achieved with heat and controlled humidity (around 80% RH); dye staining (rhodamine, basic yellow 40) follows.

Powder application suits non-porous, dry surfaces; powder choice depends on substrate color and texture; magnetic powders are used on smooth or flexible surfaces.

Iodine fuming is a reversible, temporary visualization best used on porous or thermal paper and must be photographed or fixed immediately.

Silver nitrate reacts with chloride (salt) deposits and is used on porous items such as wood and paper; it is typically applied after ninhydrin.

Sequencing matters: a reagent used out of order can destroy or mask later development; document each step and any negative result.

Chain of custody records every transfer of evidence: who, what, when, and where; gaps are documented and explained, not omitted.

Evidence packaging must prevent contamination and loss: porous items in paper, non-porous in paper or breathable containers; never seal damp items in plastic.

Quality assurance includes proficiency testing, case review, and documented corrective action when errors are found.

Examiners must disclose conflicts of interest, prior involvement, and any limitation on the examination in the report.

Reports state the conclusion, the basis (features compared), and any limitations; they avoid statistical probability language for individualization.

Testimony is limited to the examiner's own analysis and the discipline's accepted methodology; the examiner does not opine beyond the scope of the examination.

Laboratory accreditation (e.g., ISO/IEC 17025) and certification (e.g., IAI certification) are separate: accreditation applies to the lab, certification to the individual.

Documentation must be sufficient for an independent examiner to reconstruct the analysis without the original examiner's presence.

Bias mitigation includes linear sequential unmasking: the examiner analyzes the latent before seeing the known print, and any exposure is documented.