Firearms IdentificationFirearms IdentificationThe class characteristics obtained from an evidence

bullet can narrow down the possibilities of the use of a certain type or make of weapon.

However, the evidence bullet must be compared to a “test bullet” that has been fired from the suspect weapon in order to match individual characteristics.

Firearms IdentificationFirearms Identification

In order to prevent damage to the test bullet’s markings and to facilitate the bullet’s recovery, test firings are normally made into a recovery box filled with cotton or into a water tank.

The comparison microscope is used to compare the individual characteristics of the “evidence bullet” to those of the “test bullet”.

Both bullets are viewed simultaneously within the same field of view.

The examiner rotates one bullet until a well defined land or groove comes into view. The other bullet is rotated until a matching region is found.

Firearms IdentificationFirearms IdentificationNot only must the lands and grooves of the test and

evidence bullet have identical widths, but the longitudinal striations on each must coincide.

Firearm IdentificationFirearm Identification

The firearms examiner rarely encounters a situation in which a perfect match exists all around the bullet’s periphery.

The presence of grit and rust can to some degree alter the markings on bullets fired through the same barrel.

Firearm IdentificationFirearm Identification

As with fingerprint comparison, there are no hard and fast rules governing the minimum number of points required for a bullet comparison.

The final opinion must be based upon the judgment, experience, and knowledge of an expert.

Cartridge CasingsCartridge CasingsAll bullets have cartridge casings

that may be analyzed for breechblock impression, firing pin impression, ejector marks, and extractor marks.

Firing Pin Firing Pin ImpressionsImpressions

andandBreechblock Breechblock ImpressionsImpressions

Extractor MarkExtractor Mark

ShotgunsShotgunsMost shotguns have a smooth barrels. Therefore,

projectiles passing through a shotgun barrel will not be impressed with characteristic markings.

The diameter of a shotgun barrel is expressed by the

term “gauge”. The higher the gauge, the smaller the barrel.

ShotgunsShotguns

Gauge = the number of lead balls with the same diameter as the barrel that would make a pound.

Exception – A .410-gauge shotgun has a barrel with a 0.410 inches in diameter.

ShotgunsShotgunsShotgun “shot” or “pellet” evidence can sometimes

indicate the gauge of the shotgun.

The shotgun shell can be analyzed in the same manner as a bullet cartridge casing.

The “wad” typically flies approximately 10 – 15 feet from the shotgun barrel. If found, if can indicate the gauge of the shotgun used.

Automated Firearm Search Automated Firearm Search SystemSystem

DRUGFIREDRUGFIREThe DRUGFIRE system was developed by the FBI and has been online since 1992.

The image of the base of an expended cartridge is placed into the system. The breechblock marks and the firing pin impressions are the areas of interest for comparison.

Automated Firearm Search Automated Firearm Search SystemSystem

DRUGFIREDRUGFIREThe DRUGFIRE system also incorporates a bullet

imaging system which allows the examiner to image expended bullets into the system for comparison with other expended bullets.

Automated Firearm Search Automated Firearm Search SystemSystem

IBISIBISThe IBIS system (Integrated Ballistics

Identification System) is a technology that has been developed by the ATF (Bureau of Alcohol, Tobacco, and Firearms). It came online in 1991.

Data storage system is similar to DRUGFIRE.

Automated Firearm Search Automated Firearm Search SystemSystemNIBINNIBIN

In 1999, the FBI and ATF signed a Memorandum of Understanding allowing the use of the National Integrated Ballistics Identification Network (NIBIN) to facilitate exchange of firearms data between DRUGFIRE and IBIS.