Forensic Ballistics

The chemistry and physics inside the chamber: propellant classification (single-, double- and triple-base smokeless powders), primer types (Berdan, Boxer, lead styphnate vs lead-free), ignition mechanics from primer strike to powder combustion, and the chamber-pressure curve that decides muzzle velocity and barrel life.

What the bullet does between muzzle and target: the parabolic flight path, gravity drop and point-blank range, aerodynamic drag and ballistic coefficient, wind drift, and the long-range corrections (Coriolis, spin drift) and ranging methods (mil-dot, BDC turrets, laser rangefinders) used in modern firearms casework.

How a bullet transfers kinetic energy into a target: penetration mechanics and the hydrostatic-shock model, bullet deformation, expansion and fragmentation, wound ballistics (entry vs exit wounds, temporary vs permanent cavitation), and the standardised testing media (ballistic gelatin, NIJ Standard 0101.06, ISO 14876) that benchmark body armour and ammunition lethality.

The working firearm taxonomy a forensic examiner needs on every case: handguns (revolvers and semi-automatic pistols), long guns (bolt-action, lever, pump, AR platform, INSAS), automatic and selective-fire weapons (SMG, assault rifles, LMG), and the cross-jurisdictional classification frameworks (Indian Arms Act 1959, US ATF NFA categories, UK Firearms Act 1968 Section 1 / Section 5).

What the bench actually receives: cartridge anatomy (case, primer, propellant, projectile), the metric and imperial calibre systems, headstamp identification across civilian, military and surplus production, and the specialised ammunition classes (hollow-point, AP, frangible, tracer, less-lethal, sub-sonic) that change wound pattern and penetration outcome.

The forensic identification core of the discipline: rifling characteristics (lands, grooves, twist direction), bullet striation comparison on the comparison microscope (Leica FSC, Foster + Freeman BalliScan), cartridge-case markers (firing pin, breech-face, ejector and extractor marks), and the automated databases (IBIS / NIBIN, EBIS, INTERPOL Ballistic Information Network) that link a fired round to a previously logged weapon.

Reading the chemical signature a discharge leaves on hands, garments and surfaces: GSR composition and particle morphology (Pb / Ba / Sb spherical particles), sampling protocols (tape lifts, swabs, garment recovery) with persistence and secondary-transfer caveats, and the instrumental stack (SEM-EDS under ASTM E1588, AAS, NAA, Modified Griess, sodium rhodizonate) that anchors GSR admissibility worldwide.

Translating muzzle-to-target distance and trajectory into a reconstructable scene: range-of-firing zones (contact, near-contact, intermediate, distant) and the dermal patterns each produces, powder tattooing, stippling and blackening on skin and garments (with the Modified Griess test as the workhorse), and bullet-trajectory analysis with probe and laser methods plus ricochet interpretation.

The adjacent and specialised topics every firearms examiner is expected to handle: tool-mark identification (impressed vs striated, comparison, court presentation), improvised and country-made firearms (the Indian katta and desi tamancha, the Philippine paltik, the US 3D-printed ghost gun and FGC-9), silencers and suppressors and conversion devices, and restoration of obliterated serial numbers by chemical etching, magnetic-particle, ultrasound and laser methods.

The statutory and admissibility framework that decides whether ballistic evidence holds up in court: the Indian Arms Act 1959, Arms Rules 2016 and BNS 2023 firearm offences (§§ 117, 304); the US ATF, Brady Handgun Violence Prevention Act 1993 and NFA 1934 regime; the UK Firearms Act 1968 with its Section 1 / Section 5 categories; and the global frameworks (Arms Trade Treaty 2013, UN Programme of Action on Small Arms 2001, INTERPOL Firearms Reference Table).