Trace evidence involved in a crime scene tends to be in many different forms for example hair, fibres, soil, and glass among others. Glass analysis includes scientifically determining the speed of bullets, the direction of shots and the firearm type based on the impact of the crack on the glass. The method applied in determining the order of gunshots utilizes the scientific approach of studying the fracture lines on the points of impact on the glass. This paper discusses the methodology used to determine the order of bullets on glass evidence and the importance of the glass analysis in crime scene reconstructions.
Determining the Order of Bullets
In cases involving multiple gunshots, the pattern of the glass fractures enables the analysts to determine the order in which the bullets hit the glass. From a scientific approach, the cracks evident on the glass appear in either spiral or concentric form (Lyle, 2013). The radial cracks diverge outwards from the area of impact in a spoke-like manner. Concentric cracks appear as progressively larger circular cracks that surround the point of impact. The examiner tends to consider the termination points of the radial fracture lines to establish the order of the shots.
When the first bullet hits the glass, the point of impact appears to have both radial cracks that spread outside and the concentric cracks that form in a circular manner around the point of contact (Lyle, 2013). The radial fracture lines of the first bullet tend to extend completely from the point of impact. When the second bullet hits the glass, the point of contact also has radial and concentric cracks. However, the radial of the second crack tends to end abruptly at those created by the first bullet. The analysts can determine the third shot break since the radial fracture lines of the third tend to end on those of the second. Examiners can arrange the first, second and third bullets in chronological order.
Importance of Analysing Glass Fractures
The glass analysis is of importance in different ways. Firstly, the fragments of glass from the headlights of a car involved in a hit and run incidence can help in determining the exact car involved. Moreover, the glass pieces can be of significance to the police in identifying the possible direction of the bullets. The examiners can gather several clues from even the smallest glass fragments. Glass analysis is also necessary during the refutation of the statements from the suspects and the witnesses (Jensen & Qiang, 2009).
Hence, the findings are essential in assigning culpability. For instance, during a shooting incident involving two culprits, one of the offenders fires a bullet towards a car and starts to drive away. The accomplice also takes the same firearm and fires again. One bullet hits the driver of the other car on the shoulder and another on the head killing him. In this case, glass analysis can help in determining which bullet and from which culprit killed the victim.
Conclusion
Glass analysis is necessary during crime scene reconstruction. In an incidence involving a homicide caused by gunshots on a vehicle, the glass analysis technique applies to determine the order of the bullets. The examiners tend to observe the nature of the point of impact on the glass. The points of contacts tend to have two different types of fracture lines; radial and concentric which help in determining the order of the bullets. The glass analysis technique is also important in determining the direction of the gunshots and the type of firearms involved depending on the nature of the crack. Therefore, glass analysis is an important technique applicable during a crime scene reconstruction.
References
Jensen, R., & Qiang, S. (2009). Feature selection for aiding glass forensic evidence analysis. Intelligent Data Analysis, 13(5), 703-723. doi:10.3233/IDA-2009-0389
Lyle, D. (2013). Fast Bullets and Broken Glass. The Writer’s Forensics Blog. Retrieved 19 June 2016, from https://writersforensicsblog.wordpress.com/2013/06/14/fast-bullets-and-broken-glass/
