Forensic significance of perforation pattern in polycarbonate sheet against 9 × 19 mm projectile
Forensic significance of perforation pattern in polycarbonate sheet against 9 × 19 mm projectile

Summary/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 8 mm, 10 mm, 12 mm and 15 mm at firing ranges 5 m and 10 m when impacted against 9 ×19 mm 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 was 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 5 m range of fire the trend of crack zone becomes nearly constant from 8 mm to 15 mm thickness, however, at 10 m range of fire crack zone increases from 8 mm to 15 mm thickness. Furthermore, the diameter of the plastic zone increases as the thickness of the sheet increases (from 8 mm to 15 mm, respectively).

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