Practice

Forensic Ballistics: Applied Scenarios and Casework Decision-Making

This medium-level mock moves beyond definitions into applied scenarios and casework decisions — requiring students to select the correct interpretation, action, or conclusion for realistic forensic ballistics situations. Every question is pitched at the application level. Questions cover: class characteristic exclusion from twist direction mismatch (right vs left = categorical exclusion), GSR interpretation with low particle count after 6 hours (qualified finding; not conclusive positive or negative), discrepant cartridge case comparison results (each case reported independently; note discrepancy), fragmented bullet examination (examine all fragments; recover class characteristics; note limitations), corroded recovered firearm protocol (document + borescope + do not clean barrel + test fire if safe), range estimation from soot without stippling (close range under ~30 cm; contradicts claimed 5 m distance), trajectory reconstruction using rods in bullet holes (convergence point = shooter position), firing pin impression: class agreement but individual disagreement = exclusion conclusion, shotgun pattern range estimation by interpolation (30 cm pattern between 3 m/22 cm and 6 m/45 cm = ~4 m), glass bullet hole cone direction (wider cone indicates exit surface; bullet direction through glass), cartridge case forensic value without a bullet (firing pin + breech face + extractor/ejector marks + headstamp + primer type), through-and-through wound sequence (entrance = abrasion ring + inverted; exit = everted + larger; wall bullet = reduced velocity), high-velocity vs low-velocity wound ballistics (velocity squared = dominant factor; ~6x more KE in rifle vs handgun), shotgun wad forensic value (gauge + barrel marks + range indication), serial number restoration on obliterated firearm (acid etching; compressed crystal structure), wound track trajectory vs claimed shooter position (downward track inconsistent with claimed ground-level shot), skull external bevelling = exit wound, trigger pull biomechanical assessment for self-infliction (one factor; does not categorically exclude), back spatter DNA on muzzle (consistent with discharge; consider direct contact alternative), contact shotgun stellate wound (gas trapped under skin over bone; confirms contact range), IBIS candidate list workflow (human comparison microscope next step; not arrest or automatic identification), class characteristics matching multiple pistol models (report as consistent with listed models; individual comparison needed), unfired cartridge collection protocol (photograph + gloves + fingerprints + DNA + headstamp), propellant residue analysis (single vs double base + stabiliser type + manufacturer), ACE-V peer verification purpose (quality assurance; independent check; improves reliability), non-standard class characteristics suggesting country-made firearm (report specific characteristics + inconsistent with commercial database), drop-discharge claim assessment (test drop safety + model research + trajectory consistency), subjectivity challenge to firearms identification (acknowledge judgment + ACE-V + proficiency testing + error rate transparency), Berdan-primed case vs Boxer-using firearm (primer type is of cartridge not firearm; any firearm can fire either), IBIS crime-to-crime link workflow (human confirmation + investigative lead; not prosecution identification), bullet with no rifling marks (smooth-bore firearm; no comparison possible with rifled barrel), and glass fracture sequence determination (later cracks terminate at earlier cracks; first crack runs unimpeded). Themes covered: - Comparison conclusions: class exclusion, individual exclusion, inconclusive, identification criteria - Range and trajectory: soot/stippling interpretation, wound track analysis, trajectory reconstruction, shot pattern interpolation - Wound science: contact/close/distant range, through-and-through sequence, stellate wounds, skull bevelling, back spatter - Casework procedures: corroded firearm protocol, serial number restoration, unfired cartridge collection, fragmented bullet examination - Evidence interpretation: IBIS workflow, ACE-V verification, drop-discharge assessment, glass fracture sequencing, country-made firearms - Ballistic science: KE formula applied, GSR low particle count, Berdan vs Boxer in casework Each question cites Saferstein's Criminalistics 13th edition and NAS/PCAST reports. Allow 15 minutes.