Criminalistics: Trace Evidence, Fingerprints, Ballistics, Handwriting, and Technical Examination of Documents
Criminalistics
This domain tests five core criminalistic examinations and the logic linking trace, weapon, document, or writing to a source. The exam expects method names and limits, not generic crime-scene advice.
Core rules
- Trace evidence (trasology): identify mechanism and source from footprints, tool marks, tyre marks; compare class and individual characteristics; document scale and lighting.
- Fingerprints: use ridge characteristics; quality and quantity matter; partial prints may support only a qualified conclusion; avoid absolute identification language without basis.
- Ballistics: identify weapon, cartridge, trajectory, and firing distance; preserve cartridges and bullets; test-fire controls; distinguish class from individual marks.
- Handwriting: assess stability, variability, and comparison samples; sufficient comparable text is required; opinion may be categorical or probabilistic; do not diagnose the writer character.
- Technical document examination: detect alterations, erasures, additions, printing and toner, paper, and document age; use appropriate light and chemical methods; preserve the document.
Worked example
A questioned signature on a contract is compared with 15 known signatures. The expert checks writing pace, pressure, connecting strokes, and letter forms, then evaluates whether differences exceed natural variation. If the known samples are photocopies, the expert should request originals; otherwise the conclusion is limited. The reasoning links sample quality to the strength of the opinion.
Traps
- Comparing a photocopy with an original as if equivalent.
- Overstating a partial fingerprint.
- Confusing class with individual ballistics characteristics.
- Treating handwriting analysis as personality assessment.