Ballistic Expert Evidence under the Bharatiya Sakshya Adhiniyam, 2023: Firearm Identification, Range, Trajectory and Evidentiary Value

Where a firearm has been used, ballistic evidence is capable of doing something no witness can do: connecting a particular weapon to a particular discharge. A rifled barrel leaves marks on every bullet that passes through it, and the breech face and firing pin leave marks on every cartridge case, and these marks are treated as individual to the weapon. Where the weapon has been recovered and the projectile is available, the failure to produce that evidence tells heavily against the prosecution.

1. What Ballistics Covers

Forensic ballistics is conventionally divided into three branches, and each answers a different question in a criminal trial.

Internal ballistics concerns what happens inside the weapon — the ignition of the propellant, the passage of the projectile along the barrel, and the marks impressed on the projectile and the cartridge case in the process. This is the branch that produces identification evidence.

External ballistics concerns the flight of the projectile — its trajectory, its velocity, its stability, and the effect of distance and obstruction. This is the branch that answers questions about the position of the firer and the direction of fire.

Terminal or wound ballistics concerns what happens when the projectile strikes — the nature of the wound, the presence or absence of an exit, the deformation of the projectile, and the residues deposited around the entry. This is the branch that overlaps with medical evidence, and the two must be read together.

A ballistic expert gives evidence under Section 39(1). The grounds of his opinion are relevant under Section 45, which is what permits him to be examined about his method, and facts supporting or contradicting the opinion are relevant under Section 40.

2. Firearm Identification

The identification of a firearm rests on marks of two kinds, and the distinction between them determines what the evidence establishes.

Class characteristics are shared by every weapon of a type — the calibre, the number of grooves cut into the barrel, their width, and the direction of twist. Two bullets with different class characteristics cannot have come from the same weapon; two with the same class characteristics may have come from any weapon of that type. Class characteristics therefore exclude, but do not identify.

Individual characteristics are the microscopic irregularities left by the manufacture, use and wear of a particular barrel. As the bullet passes through, these irregularities score fine longitudinal striations on its surface, and the pattern is treated as unique to that barrel. Comparison of the striations on a recovered bullet with those on a test-fired bullet from the suspect weapon is what produces identification.

The same reasoning applies to the cartridge case, on which the breech face, the firing pin, the extractor and the ejector leave their own marks. A cartridge case recovered from the scene may be matched to a weapon even where the bullet is not recovered or is too damaged for comparison.

3. Range of Fire

Determining how far the firer stood from the victim is one of the most useful things ballistic and medical evidence do together, because it frequently decides between competing accounts of the occurrence — self-defence, accident, or execution at close quarters.

The determination rests on what a discharge deposits around the entry wound in addition to the projectile. At contact range the muzzle is against the skin, and the gases enter the wound, producing a ragged and blackened entry, sometimes with the impression of the muzzle. At close range the flame scorches and singes, and unburnt and partially burnt propellant particles are driven into the skin, producing tattooing or stippling, with blackening from soot. As the distance increases these signs disappear in a predictable order — soot first, then tattooing — until at longer ranges nothing is left but the projectile wound itself.

With a shotgun the corresponding indicator is the dispersion of the pellets. At very close range the charge enters as a single mass, producing one large wound; as distance increases the pellets spread, and the diameter of the pattern grows in a manner that can be reproduced by test firing the same weapon with the same ammunition.

Two cautions attach to all of this. The distances at which each sign appears depend on the weapon, the ammunition and the barrel length, and an opinion should therefore rest on test firing the actual weapon with comparable ammunition rather than on general tables. And clothing intercepts residues, so that an entry through cloth may show none of the signs even at close range — a point that must be put to the expert where the deceased was clothed at the point of entry.

4. Direction, Trajectory and Position

The direction of fire is established from the relationship between the entry and exit wounds, the track through the body described in the post-mortem, and the position of any bullet holes in clothing, walls, furniture or vehicles.

Where these are read together they may establish the position of the firer relative to the deceased — whether the shot was fired from above or below, from the front or behind, and whether the deceased was standing, sitting or prone. This is frequently the decisive evidence where the defence is that the discharge was accidental or occurred during a struggle, because those accounts imply a particular geometry, and the physical findings either fit it or they do not.

The reconstruction depends on findings recorded by others — the post-mortem track, the site plan, the position of holes and marks at the scene. A ballistic expert reconstructing a trajectory is working from that material, and the reconstruction is only as good as the record. Where the site plan is inadequate, or the post-mortem does not describe the track, the reconstruction rests on assumption.

5. Gunshot Residue

Discharging a firearm deposits residue on the hands and clothing of the firer, and its detection is sometimes relied upon to show that a particular person fired. The evidence must be handled with care, because residue is a class indicator and transfers readily.

Its presence establishes that the person was in proximity to a discharge, handled a discharged weapon, or came into contact with a surface bearing residue. It does not establish that he fired. Its absence is equally weak in the opposite direction, since residue is lost rapidly by washing, wiping and ordinary activity, and the interval between the occurrence and the sampling is therefore critical.

Where such evidence is relied upon, the matters to establish are when the sample was taken, what the accused had done in the interval, how the sample was collected and preserved, and whether he had been in contact with police personnel or vehicles where residue might innocently have been transferred.

6. The Duty to Produce the Expert

Where a firearm has been recovered and sent for examination, the prosecution is expected to produce the ballistic evidence connecting it with the offence. Failure to do so is not a technicality; it leaves a gap the court cannot fill by assumption.

The obligation is not absolute, and its force depends on what else is available. Where the weapon was never recovered, no comparison is possible and no adverse inference arises from the absence of ballistic evidence. Where the weapon was recovered but the projectile was not, or was too deformed for comparison, the expert can still speak to class characteristics and to range, and should be produced for that purpose. It is the case where both weapon and projectile are available, an examination has been conducted, and the report is not produced, that attracts the full force of the principle.

7. Ballistic and Medical Evidence Together

Neither branch is sufficient by itself where a firearm is involved, and the two must be read as a pair.

The medical evidence establishes the wound — its situation, the presence or absence of blackening, tattooing and singeing, the track through the body, the presence of an exit, and the projectile recovered from the body. The ballistic evidence establishes what weapon could have produced such a wound, at what range, and whether the projectile recovered came from the weapon in question.

The chain that connects the accused to the death therefore has two links, and both must hold. The ballistic expert connects the recovered weapon to the recovered projectile; the medical officer connects the projectile to the injury and the injury to the death. Where either link is missing — the projectile not recovered, or the weapon not examined, or the track not described — the chain is incomplete, and the remaining circumstances must carry more weight.

Where the two branches conflict, the conflict must be resolved rather than ignored. A ballistic opinion that the weapon was fired from more than ten feet cannot stand with a medical finding of dense blackening around the entry, and one of the two opinions must be wrong. Section 40 makes the material bearing on each relevant, and the resolution is a matter for the court applying the criteria the experts have supplied.

8. What Must Be Proved

As with all forensic evidence, the report establishes what was examined. Connecting the examined articles to the accused and the occurrence requires ordinary proof.

1. Recovery of the weapon — from where, from whom, in what circumstances, and under which provision. Where it was recovered at the instance of the accused, the requirements of the proviso to Section 23(2) apply.
2. Recovery of the projectile or cartridge case — from the body at the post-mortem, or from the scene at the time of inspection, with the person who recovered it examined.
3. Sealing and custody of both, separately, with the seals described and specimen seals preserved.
4. Transmission to the laboratory in sealed condition, with the carrier examined and the receipt proved.
5. Condition on receipt — that the seals were intact and matched the specimen.
6. The examination itself — the method of comparison, whether the weapon was test fired, what ammunition was used, the number and quality of the matching striations, and whether any unexplained differences were observed.

The weapon and the projectile should have been sealed and transmitted separately. Where they travelled together, the objection that marks may have been transferred in transit is available, and it is difficult to answer once made.

9. Limitations

Five limitations recur, and each should be put to the expert in a contested case.

A smooth-bore weapon cannot be individualised from the projectile, which removes the strongest form of the evidence in a large proportion of Indian cases.

A deformed projectile may not bear comparable striations. A bullet that has struck bone or a hard surface may be too damaged for comparison, and an opinion based on a badly deformed projectile should be scrutinised for how much of the surface was actually compared.

A match connects the weapon, not the hand. Ballistic evidence establishes that a particular weapon fired a particular projectile. Who was holding it is a matter for the other evidence entirely.

Range determination depends on test firing the actual weapon. An opinion founded on general propositions about the distances at which blackening or tattooing appear, without test firing, is considerably weaker, and the point should be taken.

Time and condition affect the examination. A weapon fired again after the occurrence, cleaned, or damaged in the interval may no longer produce marks comparable with the recovered projectile, and the history of the weapon between recovery and examination is therefore material.

10. The Position Stated Shortly

1. Ballistic evidence is expert opinion under Section 39(1), tested through Sections 40 and 45.
2. Class characteristics exclude; individual characteristics identify. Only rifled weapons produce striations capable of individual identification.
3. Cartridge cases may identify a weapon even where the bullet cannot, through breech face and firing pin marks.
4. Range is determined from blackening, tattooing, singeing and pellet dispersion, and an opinion should rest on test firing the actual weapon.
5. Gunshot residue is a class indicator. Its presence shows proximity to a discharge, not that the person fired; its absence proves very little.
6. Where a weapon has been recovered and examined, the expert must be produced — Sukhwant Singh — and an unexplained failure affects the creditworthiness of the case.
7. Ballistic and medical evidence form a two-link chain, and both links must hold.
8. A match connects the weapon and not the hand, and the remaining circumstances must establish who fired it.

11. Related Topics and Provisions