Forensic Firearm Comparison and Ballistics

To evaluate whether fired bullets or cartridge cases could have originated from the same firearm, using their observable characteristics and validated examination methods.

An optical instrument that allows an examiner to view two specimens simultaneously for side-by-side comparison of surface detail.

To obtain known specimens for comparison with questioned bullets recovered during an investigation.

To obtain known examples of firing pin, breechface, extractor, ejector, and other marks produced by a submitted firearm.

A device commonly using water to decelerate and capture fired projectiles while minimizing damage to their surfaces.

A controlled projectile-capture device using suitable stopping material to recover test-fired bullets.

Damage to the bullet can obscure the striations and impressions needed for meaningful firearm comparison.

A method of assessing runs of corresponding striations in toolmark comparisons, subject to its methodological limitations.

No. A source conclusion requires evaluation of the quality, significance, and potential alternative explanations for the observed correspondence.

A comparison involving known firearms or specimens to determine whether particular sources can be excluded from consideration.

A result in which the available characteristics do not support either a source association or an exclusion under the applicable criteria.

A conclusion that two specimens did not originate from the same relevant source, based on sufficient incompatible characteristics.

They establish compatibility with a class of firearms but do not independently demonstrate a common firearm source.

Damage may reduce the amount of usable microscopic detail and limit the strength of any comparison conclusion.

Comparing marks produced during chambering, firing, extraction, and ejection with known or other questioned specimens.

A controlled examination of a firearm's mechanical operation, condition, and relevant safety or firing characteristics.

Its original condition may be relevant to the investigation and could change during handling or examination.

An assessment of a firearm's condition and mechanisms in relation to a claim that it discharged without an intentional trigger operation.

No. Mechanical findings may inform the investigation but do not independently establish a person's intent.

The force required to operate a firearm's trigger under specified measurement conditions.

It may affect firearm function, discharge characteristics, and the interpretation of an alleged firing event.

Particles or chemical residues produced or dispersed during firearm discharge.

Residue containing inorganic particles derived from primer, ammunition, firearm, or environmental materials.

Residue containing organic compounds associated with propellants and other ammunition components.

Scanning electron microscopy with energy-dispersive X-ray spectroscopy is used to examine particle morphology and elemental composition.

A particle whose elemental composition and morphology meet defined criteria associated with firearm discharge under the applicable analytical scheme.

Residue can result from firing, proximity to a discharge, contact with contaminated objects, or secondary transfer.

Residue may not deposit, may be lost through activity or washing, or may fall below the detection capability of the examination.

Longer delays and intervening activities can reduce the amount of recoverable residue.

To collect particles from a selected surface for subsequent microscopic and elemental examination.

The evaluation of firearm discharge effects to estimate the muzzle-to-target distance under relevant conditions.

A wound produced when the firearm muzzle is against or in contact with the target at discharge.

A wound associated with discharge effects such as deposited powder particles or stippling at distances where these effects can reach the target.

Small punctate abrasions caused by unburned or partially burned propellant particles striking the skin.

Dark residue from firearm discharge that may accumulate on a nearby target surface.

They permit comparison of questioned residue patterns with patterns produced using relevant firearm and ammunition combinations at known distances.

Clothing may intercept soot, powder particles, and other discharge effects before they reach the skin.

The evaluation of projectile paths using physical evidence, geometry, and other relevant scene information.

A device used to illustrate or measure an apparent projectile path through suitable aligned defects.

They represent an estimated path through observed defects and may not account for projectile deflection, deformation, or movement of objects.

The angle at which a projectile approaches a surface relative to a specified reference plane or normal.

Impact forces, target properties, projectile shape, and deformation can cause deflection or ricochet.

A mark produced when a tool or object contacts another surface and transfers or alters surface detail.

An impressed mark results mainly from pressure, while a striated mark results mainly from sliding contact.

Doing so may damage or alter the original mark and compromise subsequent comparison.

To preserve a three-dimensional representation of an impression for examination and comparison.

Whether the differences support exclusion or indicate another issue; apparent microscopic similarities must not override reliable incompatibilities.

The clothing bears residue associated with firearm discharge, but the result alone does not establish that the passenger fired the weapon.

The door impact may have deflected or destabilized the projectile before it reached the wall.

The actual examination findings, the supported conclusion, the method used, and relevant limitations without overstating certainty.