Forensic Ballistics: Tool Marks: Class, Sub-Class and Individual Characteristics

UGC-NET Forensic Science Paper II Unit V drill on tool-mark examination at the application band, working through the three AFTE characteristic levels that decide every comparison conclusion. Items step through the three tool-mark categories (impressed marks from compression contact, striated marks from sliding contact, and combination marks that carry both), the class characteristics that narrow a recovered mark to a tool type (chisel, screwdriver, pry bar, bolt cutter, drill bit) with their dimensions and working-surface profile, the sub-class characteristics that arise from shared manufacturing batches (consecutively manufactured tools, a common broach or grinding wheel, mould flash lines) and that an inexperienced examiner can mistake for individual features, and the individual characteristics, the random microscopic irregularities and wear patterns unique to one tool, that allow source identification. Casework recovery covers Mikrosil silicone polymer casting on hard substrates, dental impression materials (alginate, polyether, polyvinyl siloxane) on softer dental-style impressions, and the electrostatic dust mark lifter for dry residue patterns. Comparison microscopy covers the dual-stage bridge with split-field view and the AFTE Range of Conclusions scale (Identification, Inconclusive, Elimination, Unsuitable).

Designed for MSc and BSc forensic-science students sitting UGC-NET Paper II, NFSU MSc entrance, FACT aptitude, and central FSL Ballistics-Division recruitment, the set also serves State FSL examiners refreshing the sub-class versus individual distinction before report-writing. Indian casework anchors cover housebreaking (chisel and screwdriver marks on doors and almirahs), vehicle theft (lock-pick marks on ignition cylinders), and safe-breaking (drill bit and oxy-acetylene torch cuts on vault doors).

Topics covered:

• Tool-mark categories: impressed, striated and combination
• Class characteristics: tool type, dimensions, working-surface profile
• Sub-class characteristics: consecutive manufacture and batch features
• Individual characteristics: random irregularities and wear patterns
• Casting media: Mikrosil silicone, dental impression materials
• Electrostatic dust mark lifting for residue patterns
• Comparison microscopy and AFTE Range of Conclusions
• Indian casework: housebreaking, vehicle theft, safe-breaking

Near-twin distractors test whether you can separate sub-class from individual without collapsing the two, and whether you can place a mark on the AFTE scale correctly. Allow 30 minutes.