Identifying Firearms & Toolmarks

The best thing is to call and discuss your case.  An experienced firearm examiner has a significant amount of insight into examining seemingly unusual evidence.  In addition, they may have suggestions for testing or examinations of the evidence that are not readily apparent at the onset.

A well trained and experienced firearm examiner, with a strong science background and critical thinking skills is able to design experiments to test or recreate a particular situation, circumstance or occurrence.  These experiments are necessary to support or refute statements with facts and data, not just opinions or anecdotes.

A discipline of forensic science which has as its primary concern to determine if a bullet, cartridge case, or other ammunition component was fired by a particular firearm.

Well partly…  Ballistics is the science of projectiles in motion.

It is usually divided into three parts:

• Interior Ballistics – which studies the projectile’s movement inside the firearm,
• Exterior Ballistics – which studies the projectile’s movement between the muzzle and the target,
• Terminal Ballistics – which studies the effect of a projectile’s impact at the target.

Ballistics is a term often confused with Forensic Firearms Identification.

An assembly of a barrel and action from which a projectile(s) is propelled by products of combustion.

A single unit of ammunition consisting of the cartridge case, primer, propellant and one or more projectile(s).

A non-spherical projectile for use in a rifled barrel.

A handgun in which the chamber is integral with the barrel.

A pistol that is a repeating firearm that requires a separate pull of the trigger for each shot fired, and which uses the energy of discharge to perform a portion of the operating or firing cycle.  Also known as an autoloader or self-loader.

A firearm, usually a handgun, with a cylinder having several chambers so arranged as to rotate around an axis. The firearm is discharged successively by the same firing mechanism. They can be double action, single action or both.

A firearm with a rifled bore designed to be fired from the shoulder.

Helical grooves cut or impressed into the bore of a firearm barrel to impart rotary motion to a projectile when fired. As the projectile or bullet travels down the barrel, the rifling will also engrave the surface of it with a pattern of lines. This pattern can be used to identify a bullet as having been fired by a particular firearm.

A long gun designed to shoot from the shoulder, typically having a smooth bore and designed to fire shotshells. Shotgun calibers are described as a gauge.

It is a term used in the identification of a shotgun bore. The gauge is equal to the number of round lead balls of bore diameter that equal one pound. Thus 12 gauge is the diameter of a round lead ball weighing 1/12 pound.

It is a term used to designate the specific cartridge for which a firearm is chambered.

In firearms, caliber is the approximate diameter of the circle formed by the tops of the lands of a rifled barrel, typically expressed in hundredths of an inch (38 caliber) or millimeters (9mm caliber).

In ammunition, caliber is a numerical term, without the decimal point, included in a cartridge name to indicate the nominal bullet diameter.

The inadvertent discharge of a firearm as a result of some failure on the part of the firearm. Accidental discharge is often caused by a safety device that was broken, deficient, compromised, or missing from the firearm that, if present and operative, would have prevented the discharge.

Yes, a function test of the firearm can be done. A function test is the examination of a firearm concerning its mechanical condition and operation. It is usually done to determine if all safety features or mechanisms are operable and/or if the firearm is capable of firing a cartridge.

A device on a firearm intended to help provide protection against accidental discharge under normal usage when properly engaged. Such a mechanism is considered “on” when the position of the safety device is set in a manner to provide protection against accidental discharge under normal usage. Such a mechanism is considered “off” when it is set to allow the firearm to be discharged by a normal pull of the trigger.

A manual safety is one that must be manually engaged and subsequently disengaged to permit normal firing. An automatic safety is one that goes to the “on” position when the action of the gun is opened. A passive safety is in place (or “on”) until the trigger is pulled.

The process of determining the distance from the firearm, usually the muzzle, to the target is based upon patterns of gunpowder or gunshot residues deposited upon that target. Where multiple projectiles, such as shot, have been fired, the spread of those projectiles is also indicative of distance.