Towards the investigation of shooting incidents: evaluation of fracture pattern on polymethylmethacrylate sheet made by .22 and .177caliber air rifle.

Scientific examination of the physical evidence provides significant information beyond a reasonable doubt. Due to the increasing use of the glassy polymer i.e. polymethylmethacrylate instead of glass, the probability of the occurrence of the fractured polymethylmethacrylate sheet in a shooting incident cannot be ignored. Analysis of fracture pattern offers several analytical approaches that assist the forensic investigator. The use of air guns in criminal activities is increasing as well as these weapons have found to be fatal for living beings. This study was conducted to evaluate the fracture pattern on the polymethylmethacrylate by using an air rifle. The fracture pattern formed on polymethylmethacrylate sheets by the air guns shows some specific characteristics that may help to reconstruct the crime scene. The polymethylmethacrylate sheets were test-fired with Spring-Piston air rifles of .22″ (5.5 mm) and .177″ (4.5 mm). Data obtained from the measurements were then statistically analysed with the Chi-Square test. A consistency in hole diameter was observed. Analysis of fracture patterns may provide a lead to the investigator and may help to reconstruct a shooting incident. It can also distinguish between the standard firearm and air gun. The fracture on polymethylmethacrylate sheets gave significant findings that may efficaciously contribute to the forensic investigation of shooting incidences.