Module 5 · Medico-Legal Aspects
Firearm Injuries: Entry, Exit, Range and Pattern
Reading firearm wounds in Indian forensic casework: entry vs exit, contact to distant range signs, GSR collection, country-made kattas, and bullet recovery.
Practice with national-level exam (FACT, FACT Plus, NET, CUET, etc.) mocks, learn from structured notes, and get your doubts solved in one place.
Reading firearm wounds in Indian forensic casework: entry vs exit, contact to distant range signs, GSR collection, country-made kattas, and bullet recovery.
A firearm wound is one of the few injuries where the medical examiner is expected to read a range estimate, a direction of fire and sometimes a weapon class straight off the skin. The information is sitting there in a centimetre of tissue: soot, unburnt powder, a muzzle imprint, an abrasion collar, a stellate tear. Each of those signs maps to a specific range bracket the FSL ballistics division can then test against. The autopsy table is doing half of the ballistics work before the bullet is even recovered.
The Indian context complicates the clean textbook picture. Country-made firearms ("kattas") dominate the murder caseload in large parts of UP, Bihar, Jharkhand, West Bengal and rural Maharashtra, and they produce wound patterns that don't always match the European and American casebooks the syllabus is built on. Smooth-bore, low-pressure, often single-shot, often loaded with mixed shot or cut pieces of metal. The exam still asks the textbook signs. The fieldwork asks you to recognise when the textbook doesn't apply and to say so on the post-mortem report.
What the syllabus tests and what the casebook actually carries.
The first division a forensic student needs cold is smooth-bore vs rifled. A shotgun and a country-made katta have unrifled, smooth interiors; they fire pellets, shot, or in the country-made case whatever the maker has loaded into a paper cartridge. A rifle or handgun has a rifled bore that imparts spin to a single bullet for gyroscopic stability. The rifling produces the land-and-groove marks that the FSL ballistics division reads off the recovered projectile.
| Feature | Smooth-bore | Rifled | Country-made (typical) |
|---|
Every part of a cartridge tells the analyst something different.
A modern centre-fire cartridge has four parts and each part is forensic evidence in a different way. Identify the parts on a recovered round and you can already say something about the weapon that fired it.
In country-made cases the cartridge is often a re-loaded shotgun shell with paper wadding, mixed shot and black powder. The paper wad recovered from the wound is itself evidence; it carries powder residue, matches the loader's pattern, and sometimes carries newspaper print that can be tied to a region.
Read the skin and you get the range bracket.
The entry wound carries the range cues a forensic pathologist is trained to read. Four canonical brackets, each with characteristic skin findings. Memorise these; the FACT paper tests them every year.
Contact shot. Muzzle pressed against the skin at firing. Expanding gas drives into the wound and back-pressures into the surrounding tissue, producing several distinctive signs:
Close shot (roughly 0 to 15 cm). Muzzle near but not touching the skin. Soot is the dominant sign, with tattooing layered over it:
Intermediate shot (roughly 15 to 60 cm). Soot does not reach the skin but unburnt powder grains do.
Distant shot (beyond 60 cm). Neither soot nor unburnt powder reaches the skin.
Exit wounds answer a different question.
Exit wounds rarely carry range cues. They answer a different question: where did the bullet go after entering, what did it do on the way, and what shape did it leave when it broke through the skin on the far side. Four reliable differences from the entry.
Track analysis is the connective tissue between entry and exit. The pathologist documents the direction of fire (front-to-back, left-to-right, downward, etc.), the organs and structures along the track, the type of internal damage at each, and any deflections off bone. Direction of fire becomes critical when the scene reconstruction is being built against a suspect's account. A claimed self-defence shot from below upward, with an actual track running downward through the body, is a reconstruction inconsistency that breaks the suspect's story.
Different physics, different range cues.
Shotgun and rifled-weapon wounds need to be treated as two different problems past about 60 cm. Pellet dispersion does work for shotguns that muzzle effects don't, and rifling marks do work for rifled weapons that pellet dispersion can't.
Shotgun-specific patterns. A 12-gauge shotgun firing No. 6 birdshot from contact range produces a single round hole roughly the size of the bore (about 18 mm). As range increases, the pellets spread according to choke and load. A rough teaching rule on Indian shotgun loads is that the pellet spread diameter at the target equals about 1.5 cm per metre of range at close to intermediate distances, with choke and load type modifying the slope. At 1 to 3 metres the entry is a central hole surrounded by satellite pellet wounds. Beyond 3 to 4 metres the pellets arrive as a loose pattern with no central hole. The shot cup and wadding behave differently and can land short of the body or stay in the wound; their location is part of the range estimate.
Rifled-firearm specifics. A recovered bullet carries class characteristics: the number, width and twist direction of lands and grooves, and the twist rate (e.g. 1:10, 1:14). These are matched against a database of known weapons to narrow the suspect weapon type. The actual one-to-one match comes from individual marks: microscopic striations from imperfections in the bore, and on the cartridge case, breech-face and firing-pin impressions. The CFSL Chandigarh and Hyderabad ballistics divisions, and the major state FSLs at Mumbai, Kolkata, Chennai and Lucknow, have comparison-microscope workflows and IBIS-equivalent reference setups for these matches.
From the shooter's hand to the magistrate's seal.
Three loose threads to tie off: gunshot residue collection, distinguishing homicide from suicide from accident, and the packaging discipline that gets a recovered bullet into court.
Gunshot residue (GSR). When a firearm discharges, microscopic particles of primer residue (antimony, barium, lead) and burnt propellant escape from the breech, muzzle and any gaps in the cylinder or action. They settle on the shooter's web of the hand, dorsum of the hand, face, hair and clothing. GSR is collected with adhesive carbon stubs or wet swabs and analysed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). The signature particle is a roughly spherical Sb-Ba-Pb fused particle; finding even a few is highly indicative of recent discharge.
Medico-legal differentiation of manner of death.
| Feature | Suicidal | Homicidal | Accidental |
|---|---|---|---|
| Range | Contact (typical) | Close to distant |
Which combination of findings on an entry wound is most diagnostic of a contact-range firearm discharge?
| Bore interior | Smooth | Spiral grooves (lands and grooves) | Smooth, often rough |
| Projectile | Shot / pellets | Single bullet | Mixed; pellets, scrap metal |
| Chamber pressure | Low-moderate | High | Low, inconsistent |
| Range cue on wound | Pellet dispersion | Muzzle effects (soot, tattooing) | Atypical; both partial |
| Class marks on projectile | None usable | Lands, grooves, twist | None usable |
| Typical Indian use | Sport, rural defence | Service weapons, licensed | Murders, faction violence |
| Range bracket | Approx distance | Muzzle imprint | Soot | Tattooing | Abrasion collar |
|---|---|---|---|---|---|
| Contact | 0 cm (touching) | Yes | Deep in wound | Variable | Yes |
| Close | 0 to 15 cm | No | On skin (wipeable) | Yes (under soot) | Yes |
| Intermediate | 15 to 60 cm | No | No | Yes (spread) | Yes |
| Distant | > 60 cm | No | No | No | Yes |
| Feature | Entry wound | Exit wound |
|---|---|---|
| Size | Smaller, usually circular | Larger, often irregular |
| Abrasion collar | Present | Absent (except shored exit) |
| Soot or tattooing | Present in close/intermediate | Absent at any range |
| Margins | Inverted (pushed inward) | Everted (pushed outward) |
| Shape | Round / oval at distance, stellate at contact | Slit-like or stellate, irregular |
| Bullet recovery | Sometimes (lodged within) | Bullet has left the body |
| Variable |
| Site | Right temple (right-handed), hard palate, chin, mid-chest | Anywhere; often back of head, face, chest | Variable; cleaning-related often hand or thigh |
| Weapon at scene | In or near the deceased's hand | Often absent or planted | Present |
| Number of shots | Usually one | One or many | Usually one |
| Track direction | Front-to-back or upward, anatomically reachable | Any direction | Variable |
| Surrounding context | Locked room, note, prior history | Scuffle signs, defence injuries | Cleaning kit, recent purchase |
Bullet recovery and forwarding. In Indian practice this is governed by the same sealed-packet protocol that applies to all physical evidence, with two firearm-specific tightenings:
Bullet forwarding ties this topic back to the broader handling discipline covered in Processing Physical Evidence at the Scene and the documentary integrity covered in Chain of Custody. The autopsy work itself is covered in Autopsy and Post-Mortem Examination.