Analysis of glass fracture pattern made by .177″ (4.5 mm) Caliber air rifle

摘要

Glass is the hard, amorphous solid. Glass fragments may be an evidence of great value encountered in the investigation of various types of offences. At the scene of occurrence, the glass may be fractured either as an intentional act or due to accident. Glass fractures are of paramount importance in shooting cases where firearm is used as it can provide significant information related to the occurrence and facilitates a variety of evaluations. In fact, fractography i.e. analysis of fracture pattern, is the means and methods for characterization of fractured units or fragments in order to study or identify the mechanism of such fractures. The study of fracture pattern of glass has been of long interest to the forensic community. The glass fracture pattern analysis is very useful to establish the sequence of events and to link together items of evidence and it is of paramount importance in such cases where firearm is used. Now, the use of air guns in criminal activities is an alarm to the law enforcement agencies. The main objective of this work is to analyze the pattern of the fractures on windowpane of various thicknesses with regular .177″/ 4.5 mm lead pellet fired through the .177″/ 4.5 mm caliber Air Rifle manufactured in India. The window panes were kept at front, perpendicularly and away at a fixed distance from the muzzle end of Air Rifle. Samples were measured and analyzed on some fixed parameters. To analyze the consistency, measurements were analyzed graphically and statically checked for the goodness of fit (Chi-Square Test). The graphical representation of the measurements of different samples shows regularity in the features and Chi Square test gives very significant information regarding the consistency. The hole diameter is ranging from 4.77 to 7.5 mm in case of air rifle. It can lead to distinguish the weapon by which fracture was made, whether it is standard or air weapon. The outcomes of this work on the windowpane by .177″/4.5 mm air rifles may be efficacious to forensic community.