Determination of Range of Firing in Firearm Cases

Range determination converts the wound pattern and the clothing examination into a distance band that tells the investigator and the court whether the shot was muzzle-on-skin (strongly suggestive of suicide or close-quarter homicide), from within arm's reach, or from across a room. Under the Bharatiya Nyaya Sanhita 2023, the line between culpable homicide and murder, and between murder and an accidental discharge defence, often hinges on this single estimate.

NTA tests the topic as a four-category frame for handguns and rifles. The categories are wound-pattern bands that shift with the weapon, the cartridge and the clothing, not rigid distances. Learn the diagnostic signature of each band first.

1. Contact shot. Muzzle in skin or clothing contact. Stellate wound from sub-dermal gas tracking, muzzle imprint, seared skin, soot deposited inside the wound track, cherry-red discolouration of underlying tissues from carbon monoxide binding to haemoglobin and myoglobin.
2. Close shot. Muzzle roughly within 15 cm (6 inches) of the target for a handgun. Heavy soot blackening around the entry, dense powder tattooing under the soot, scorching and singed hair. Soot is wipeable; tattooing is not.
3. Intermediate shot. About 15 cm to 60-90 cm for handguns, longer for rifles. No soot, but a clear powder-tattooing (stippling) pattern from propellant grains embedded in the skin. Tattooing without soot is the pathognomonic finding for this range.
4. Distant shot. Beyond the reach of propellant grains, typically over about 90 cm for handguns and over a metre for rifles. Only the bullet wound, the abraded collar and (on clothing) the bullet wipe.

The bands are weapon-specific. A short-barrelled snub-nosed revolver loses powder grains faster than a long-barrelled rifle, so test firing with the same weapon and ammunition is the only honest way to fix the band.

The diagnostic test is whether powder grains have embedded in the skin (intermediate) or only soot sits on it (close) or neither is present (distant) or both plus a muzzle imprint are present (contact).

When a hard-contact shot fires, propellant gas at over 1500 degrees Celsius is forced under the skin because the skin's elasticity briefly traps it. That trapped gas produces the classic stellate or cruciate wound: skin overlying bone (skull, sternum) tears outward along radial lines because the gas has nowhere to vent but back through the skin. Soft-tissue contact shots (abdomen) produce a circular or oval wound rather than a star.

Three more findings round out the contact picture. The muzzle imprint is a contusion in the exact shape of the muzzle face, branded into the skin by recoil pushing the hot muzzle back against the wound margin. The seared margin is a ring of dried, parchment-like skin from direct heat. Soot inside the wound track, found on autopsy dissection, followed the bullet into the body. Carbon monoxide binding to subcutaneous haemoglobin and myoglobin gives the wound margin and underlying muscle a cherry-red colour that does not fade on exposure to air.

Loose-contact shots lose the stellate pattern and the muzzle imprint but keep the soot and seared margin. Angled-contact shots produce an eccentric muzzle imprint that points away from the line of fire, sometimes the only clue to the firing direction.

The close-to-intermediate boundary is where most of the careful work sits, because it is the band where soot drops out but powder grains are still reaching the skin.

Close range. Inside roughly 15 cm for a typical handgun, the cloud of hot gas, soot and partially burned propellant grains still has the momentum to deposit on the skin. The entry is surrounded by a sooty halo (2 to 5 cm across, lifts off on a damp swab), a denser tattooing pattern underneath (embedded grains, will not wipe off), and singeing or scorching of skin and hair.

Intermediate range. From about 15 cm out to 60-90 cm for handguns. Soot particles, being lightweight carbonaceous flakes, have lost momentum and no longer reach the skin. Propellant grains, denser and ballistically smoother, continue to travel and embed in the skin as a stippling pattern that spreads outward as range increases (a 30 cm shot gives a tight cluster; a 60 cm shot gives a wider, sparser one). Tattooing without soot is the single MCQ-grade diagnostic feature of this range.

A shotgun fires a charge of pellets contained in a plastic or fibre wad. Because the pellets leave the muzzle as a tight cluster and spread with distance, the geometry of the entry wound itself tells you the range. NTA tests this as a separate four-band frame.

1. Contact and very close (under about 50 cm). A single round or slightly ragged wound with intense soot, scorching and the wad recovered inside the wound. The wad is a key exhibit because it carries class characteristics of the cartridge.
2. Close intermediate (50 cm to about 1 metre). A single hole with scalloped or crenated edges where the outermost pellets have begun to peel off the main cluster.
3. Intermediate (about 1 to 3 metres). A central rat-hole (the main pellet mass) surrounded by satellite pellet hits from the outermost pellets.
4. Distant (beyond about 3 metres). No central hole, only a dispersed pattern of individual pellet wounds. The one-inch-per-yard rule for a cylinder-bore shotgun is a useful first approximation (a 30-inch spread roughly suggests a 30-yard range). Choked barrels tighten the pattern and shift the rule.

Test firing with the same shotgun, shell, shot size and choke against the same target material is essential because the spread depends on every one of those variables.

When the wound is obscured by clothing or the body has been washed, the lab turns to chemical-pattern tests on the questioned garment. Three classical tests cover the propellant nitrite pattern and the lead pattern; the same chemistry appears in the gunshot residue analysis topic of this unit.

Walker test (nitrite pattern). The classical 1940s filter-paper transfer test. Desensitised filter paper moistened with sulphanilic acid is pressed against the questioned garment for about 10 minutes so that nitrite ions transfer, then sprayed with alpha-naphthylamine. Nitrite ions diazotise the sulphanilic acid and couple with the naphthylamine to give orange-to-pink azo-dye spots that map the propellant pattern.

Modified Griess test. Current standard in most modern labs. Filter paper impregnated with sulphanilic acid plus alpha-naphthol (or N-1-naphthylethylenediamine) gives orange spots directly after transfer, without a separate spray. Same Griess diazotisation chemistry, cleaner and more reproducible than the Walker test.

Sodium rhodizonate test (lead pattern). The garment or a filter-paper lift is sprayed with sodium rhodizonate followed by a tartrate buffer. Lead deposits give a pink-to-red colour; confirmation by dilute HCl turns the spot blue-violet, excluding barium interference. Maps the lead smear from bullet surface and primer residue.

X-ray radiography of clothing. Radiopaque metal fragments, pellets and particles show up on a low-kilovoltage radiograph of the garment. Useful for shotgun cases (counting pellets and mapping the pattern) and for locating small metal fragments before sampling.

The pattern is not a distance; the distance comes from comparing the questioned pattern with patterns from test-fired control panels.

The diagnostic reading is the density and spread of the nitrite spots, compared one-to-one against test-fired control filter papers at known ranges with the same weapon and ammunition.

Range estimation is a comparison exercise. The lab reproduces the questioned pattern by test firing at known distances and compares the panels with the questioned exhibit. A defensible report depends on the discipline of the test fire.

1. Use the recovered weapon
   Test firing must use the same weapon recovered from the scene, not a similar make and model. Barrel wear, chamber dimensions and ejector geometry change the pattern enough to matter.
2. Use the same ammunition lot
   Cartridges from the same batch and box as the questioned round are preferred. Different propellant blends and primer compositions give different soot densities, grain shapes and nitrite-pattern intensities.
3. Use the same target material
   If the questioned garment is cotton, test-fire onto cotton swatches of the same weave; if leather, onto leather. Powder embeds and soot deposits differently on different fabrics.

Several India-specific factors shift the range workflow away from the textbook bands. Country-made firearms (kattas, tamanchas, pipe-guns), common in rural casework, have wide barrel-to-cartridge clearances, crude or absent rifling and irregular chamber dimensions. The result is heavy gas blow-by at the muzzle, much more soot and unburned propellant escaping forward, and patterns that look like a close shot when the muzzle was actually at intermediate range. Every test fire with a country-made weapon must use that specific exhibit; library references from factory firearms are misleading.

CFSL Chandigarh houses the central ballistics division of the Directorate of Forensic Science Services and runs the range-estimation SOP that most state SFSLs follow. The SOP requires test firing at a graded distance series, parallel chemical pattern tests, photographic comparison panels, and a range band (not a single number) as the report conclusion.

The legal stakes sit under the Bharatiya Nyaya Sanhita 2023. The line between culpable homicide and murder under BNS Sections 100 to 103, and between murder and a suicide ruling, often turns on the range estimate. A contact temple shot with muzzle imprint and stellate wound on a right-handed victim's right temple is a strong forensic argument for suicide; a distant shot from a different angle argues for homicide. The expert defends the range band under cross-examination, with test-fired panels and chemical-pattern photographs admitted as exhibits under the Bharatiya Sakshya Adhiniyam 2023.