I Firearm & Explosion 80. Under what circumstances gun powder/blackening could be detected around the entry wound? The grains of gun powder ejected from muzzle of a ired weapon may strike the skin and produce powder tattooing of the skin. Different types of gun powder exist based upon their physical con iguration: lake, disc, cylindrical, ball and lattened ball. The modern gun powders are mostly smokeless and consists of nitrocellulose (single base) or nitrocellulose combined with nitro-glycerine (double base). The ball powder may travel up to 3 feet and cylindrical powder may travel up to 2 feet. The gun powder present in the form of “powder tattooing” is suggestive of close range discharge of irearm. The gun shot residue may also be deposited on skin or items in close proximity to a weapon being ired. The blackening effect is produced by combustion of gun powder. Blackening is usually found, if a irearm is discharged from close range like a revolver or pistol discharged within about two feet. Blackening with a high power rif le can occur up to about one foot. The interposition of clothing will have an effect on the appearance of the wound, acting as a barrier which may prevent deposition of soot (blackening) or the tattooing. 81. What is abrasion collar, grease collar and dirt collar in irearm entry wound? The skin immediately around the central hole is discoloured which is called abrasion collar. The inner edge of the abrasion collar may be black as a result of heating effect and to the rubbing off of dirt, lubricating oil or grease. This is often called grease or dirt collar. It may be absent if the missile was clean and has no relation with the range of irearm weapon. MEDICAL DIMENSION OF FREQUENTLY ENCOUNTERED CASES | 58