In all firearms-related cases, efforts should be made to determine what kind of gun has been used, the distance from the victim that the gun was fired, whether the suspect really fired the gun, the possibility of accidental discharge, and if the recovered bullet has been mutilated. These questions are investigated because following discharge, every breech-loading firearm leaves physical evidence in the form of a bullet, a cartridge case, and, occasionally, firearms residue and a shot pattern. The examination of this evidence usually begins with the bullet, to identify it with the gun from which it has been fired. The cartridge case may also be linked to the gun that has fired it. Muzzle residue permits the estimation of the distance from the subject at which a gun has been fired if the discharge occurred at close range. Legal counsel should also be aware of the differentiation between 'class' (caliber) and 'individual' (relating to marks from burrs in the barrel) characteristics of bullets and cartridges, because the latter are essential to the matching of the fired bullet to the weapon which has fired it. The direction in which a bullet is fired may be determined by studying the relationship of entrance and exit wounds. For example, gunpowder residues on the skin (or outer garments) and more on one side of the bullet wound than the other indicate that the bullet has struck the body at an angle. The direction of the bullet flight path may be determined from abrasions located on fabric, wood, or human skin. In differentiating between homicide, suicide, and accidental death, it is important to determine, by means of laboratory examinations, the distance from the muzzle to the body struck, the type of firearm used, and whether or not there are firearm residues on the hand of the suspect. The attorney involved either in a prosecution or defense in which firearms evidence is used should also be familiar with the type of ammunition and the gun suspected of being used in the commission of the crime. A total of 37 references are included. See NCJ 75560-62 for related articles.