Bullet Holes in Glass Lab: Forensic Investigation

Forensic Investigation: Bullet Holes in Glass Lab

Bullet Holes in Glass

Glass broken through a projectile forms two distinct fracture types -- radial fractures and concentric fractures (Orthman & Hess, 2012). The radial fractures will often form on the glass side, on the opposite side of the impact, and will spread outwards from the point of impact (Hess & Hess, 2012). Concentric lines form after the radial fractures, on the same side of the impact, and will often encircle the point of impact (Woods, 2013). Radial fractures terminate if they encounter fractures caused by an earlier projectile, which basically means that they can be used to determine the order or sequence of force, or rather, which bullet hole was created before the other. In cases where multiple shots are fired from the opposite sides of a glass surface say a window, forensic investigators will often need to establish the order in which the shots were fired (Woods, 2013). The first shot to be fired on the surface will often produce complete and uninterrupted radial fractures, and the subsequent bullet holes will have their radial cracks terminated once they encounter cracks or fractures resulting from a previous bullet.

Applying the same procedure in determining the sequence of force in our case, we find that bullet hole E. was the first to be made on the surface. Its radial cracks are continuous and largely uninterrupted -- we do not see any occurrence where one or more of its fractures are interrupted or stopped by another fracture. This basically means that the glass surface was clear, with no pre-existing bullet holes when the shot that created bullet hole E. was fired. We can, therefore, rightly conclude that bullet hole E. was created before A, B, C, and D.

Of the remaining holes, Hole B. was created first. In the figure, we see three of hole B's radial fractures terminated by existing fractures extending from hole E, which was the first to be created. However, the rest of its radial fractures are seen to stop the radial cracks extending from holes A, C, and D. This basically means that hole B. was in existence before holes A, C, and D. In other words, the shot that created bullet hole B. was fired before the shots that created holes A, C, and D, but after that which created hole E.

Having established that hole B. was the second to be created, we now move to identifying the sequence of force of bullet holes A, C, and D. Evidently, bullet hole C. was the last to be created. Two of its radial fractures are seen to be interrupted by fractures from holes A and D. This only implies that holes A and D. were in existence before hole C. We are, however, not able to tell the order of force between bullet holes A and D. This is particularly because its radial fractures do not interact -- they are interrupted by fractures from hole B. before an interaction is made. Nonetheless, we can rightly conclude that the shot that created hole C. was the last to be fired.