Forensic Significance of Perforation Pattern In Polycarbonate Sheet Against 9 × 19mm Projectile

Abstract

Polycarbonate is widely used as structural material due to its extreme resistance to impact and perforation. In a crime involving firearms, the bullet may impact various objects fitted with or made of polycarbonate sheets leaving high chances of discovering the fractured PC sheets and fragments at the scene of crime hence these objects may become objects of the criminal investigation. In the present work the perforation pattern of PC sheets of thicknesses 8mm, 10mm, 12mm and 15mm at firing ranges 5m and 10m when impacted against 9×19mm Full Metal Jacket (FMJ) bullet were examined. It was observed that after impact the PC sheet develops entry hole smaller than the calibre of bullet; formation of crack zone, plastic zone; and petalling on the distal face were observed. It was found that as the thickness of the sheet increases, the diameter of the entry hole increases. The diameter of the exit hole initially increases and then becomes constant. At 5m range of fire the trend of crack zone becomes nearly constant from 8mm to 15mm thickness, however, at 10m range of fire crack zone increases from 8mm to 15mm thickness. Furthermore, the diameter of plastic zone increases as the thickness of the sheet increases (from 8mm to 15mm respectively).