Glass is inorganic in nature and results from the fusion that consolidates into a fragile solid when cooled. Glass is always delicate in its solid state and ought to be handled with a lot of caution. Since glass is strong in firmness and weak in strain, it easily shatters when stretched beyond its elastic point by the high velocity that may come from a stone or a bullet. In this homicide case, glass analysis will be vital to determine the sequence, direction, speed and other details from a broken glass that assists the analyst to reconstruct a crime. Glass analysis can also be used to determine the chronology of shots fired by using radial fractures of the previous shot in case of multiple shots (Swanson et al., 2013).
In this homicide case, glass analysis can provide sufficient physical evidence. Using the small shards broken from the glass, the investigator can connect the suspect with the crime scene, particularly if the suspect carried small shards in his or her hair, clothes, or skin without noticing. Glass analysis enables the investigator to determine the type of glass, the direction as well as the chronology of the shots that were fired through the glass. If the physical fractures of the glass match with that of the suspect, then it is absolutely clear that the suspect was responsible for the homicide case. Glass analysis entails evaluating types of glass on the basis of glass fragments.
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From a close look at homicide case photos, it is vividly evident that the alterations made on the glass came from a bullet. Upon analysis of the photographic evidence, the direction, as well as the order of the three bullets, was determined. Whenever a bullet makes an impact on glass, the glass absorbs the force of the bullet making it to crack alone lines that have minimal resistance. As the glass absorbs the force of the bullet, it develops a form of shock waves that create certain arrangements that damage the glass. Most analysts and investigators utilize this concept in determining the damage as well as the order of shots fired through the glass.
When a bullet hits glass, two types of diverse fractures are developed. The fractures that are developed include concentric and radial fractures that start immediately the glass is hit by the bullet. As the bullets continue penetrating the glass, the glass gives way as it breaks due to the tensional force exerted directly on the glass surface behind the bullet. At the tensional point, the force of compression at the point of tension starts. The glass then develops radiating fissures on the opposite side of the force building more pressure. This type of fractures is called radial because they move away from the point the force of the bullet was exerted. When in contact with a fracture line, radial fracture ends. On the other hand, concentric fractures start when the first bullet impact hits the glass. According to Maxwell (2011), concentric fractures occur along with the point of force entry where tension force started.
In this case, the photo revealed three entry points. After finding out these three entry points, they were marked as entry point A, B, and C respectively by the investigator. Examining these images closely, it can be noted that radial fractures at entry point A seem to link with entry point C. Additionally, the radial fractures of entry point B links with both entry points A and C while entry point C does not link with point A or B. From the look of the crime scene photos, it can be concluded that entry point C was the first one to be hit by the bullet because it is complete and does not interfere with other radial fractures.
From the photograph taken at the crime scene, it has been noted that both entries point A and B link at entry point C. Therefore, it can be inferred that the bullet that went through the glass originated from point A. It is easy to determine that entry point A was the second one to be hit by the bullet because radial fractures did not move after reaching entry point C. More so, point B was lastly hit by the bullet because the radial fractures did not stop at one point but moved at entry point A and C. As much as it has been easy to determine the entry point of bullets in this case, sometimes, it is difficult to determine bullet entry points, especially if the glass is hit severally. If radial fractures to line up at intersection points, it becomes difficult for the investigator to determine the order at which the glass hit the glass.
In determining the chronology of the shots fired, the investigator usually uses the termination points of fractures. The radial fractures of the first shot tend to extend completely as in entry point C while the other shots are cut off immediately as come in contact with the other fractures. From this homicide case, it is clear that glass analysis helps investigators in several ways. Therefore, it is important to collect and analyze fragments of glass at the crime scene because they give a clue to the analyst on the direction the bullet was fired through the glass.
References
Maxwell, V. M. (2011). Forensic Interpretation of Glass Evidence. Journal of Forensic Identification, 51(6), 597.
Swanson, C. R., Chamelin, N. C., Territo, L., & Taylor, R. W. (2013). Criminal investigation (p. 3). Boston: McGraw-Hill.
