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THE EFFECTS OF PROJECTILES ON GLASS

المؤلف:  Max M. Houck، Jay A. Siegel

المصدر:  Fundamentals of Forensic Science

الجزء والصفحة:  p446-447

2026-08-19

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THE EFFECTS OF PROJECTILES ON GLASS

Besides the chemical and physical analysis of glass particles, there are other types of evidence where glass is the matrix rather than the analyte. For example, when a piece of glass such as a window is struck by a projectile, the resultant hole(s) in the glass can yield valuable information about the direction and angle of impact. The evidence that will be available depends upon the nature and thickness of the glass and the type of projectile. If the glass is very thin or the projectile is large    or powerful, the glass will shatter. However, in the case of window glass and bullets, holes are left in the glass that can be examined. The observations that can be made include where the projectile ends up, the formation of a crater in the glass, the formation of a cone of glass, and the types and positions of cracks that appear in the glass. When a high-speed projectile, such as a bullet, passes through a piece of glass, a crater will form in the glass that is larger on the exit side of the glass. This, by itself may reveal the direction of impact of the projectile. The crater may show some asymmetry that can yield information about the angle of impact. In addition, radial cracks will form on the side of the glass opposite to the side of the impact, as shown in Figure 1. These radiate out in all directions from the point of impact. In many cases, there will also be concentric cracks on the side of the direction of impact. In addition, the orientation of stress marks in the glass at the point of the break or penetration can help determine the direction of impact. Some of the marks will form a right angle at the point of impact. The direction of the angle will indicate the direction from which the projectile came.

FIGURE 1 Radial and concentric cracks in glass and multiple penetrations in a piece of glass. Note that the radial cracks made by the second penetration stop at a crack made by the first penetration. This shows how it can be determined which penetration was made first.