Abstract:
This paper charts the student’s reaction to three videos about the use of glass in CSI forensic investigations, all narrated by Dr. Richard Saferstein, a former chief forensic scientist for the New Jersey State Police Laboratory. In these videos, Dr. Saferstein offers short explanations of the types of glass used in CSI, how they are analyzed, and the way in which this evidence is used in criminal investigations.
Keywords: CSI, forensic analysis, glass, soda-lime glass, refraction index, density, perpetrator, tempered, laminate
1. What are the different kinds of glass studied in CSI?
According to the video, there are three different kinds of glass studied in criminal science laboratories. The first is soda-lime glass, which is the most common type of glass found in things like house windows, soda bottles, and more. Soda-lime glass is typically made up of silicon dioxide, calcium oxide, and sodium oxide. The second is laminated glass, which is found on the windshield of a car, typically comprised of two layers of soda-lime glass with a plastic median. The third type is tempered glass, which is the type of glass found in all other windows of a car. Tempered glass dices and fractures instead of breaking, or at least is more resistant to breaking in that way, in order to protect the occupants of a car and preventing injury. There are other types of glass not mentioned in the video – leaded, borosilicate, and bulletproof – but they are likely not found as commonly in most CSI work, leading the video to focus on those main types that are usually found (CITE).
The video itself was very enlightening, offering a brief rundown of the major types of glass typically found in criminal investigations. Understanding the basic makeup of these types of glass, and the ways in which they differ, is a fundamentally useful piece of knowledge that can aid in basic identification of glass at the scene. This also cements the varying settings of crime scenes where glass is involved – typically cars or homes – and the breaking of glass as a common way to commit said crime. These varying types of glass evidence must be differentiated by CSI technicians if a proper comparison is to be made, and an exact link to the crime scene can be ascertained.
2. How is the analysis of glass used in CSI?
According to the video, the analysis of glass is used in CSI by looking at the physical properties of glass, such as its density and refractive index. When glass is broken during a crime, such as breaking and entering, fragments of glass are scattered around the crime scene. Sometimes, these fragments can also be caught in the clothes of the perpetrator. CSI technicians bring back these fragments to the crime lab and analyze them for their density, refractive index, and other distinguishing features, in order to link them to the crime scene or to the perpetrator.
The video itself was very short, demonstrating the basic bare-bones information needed for answering the prompt. However, it offered an appropriate starting point to discuss the use of glass analysis in CSI, and the ways in which it plays a part in criminal investigations. When it comes to CSI glass work, it typically happens on the aforementioned fragments, which are collected and brought to the lab for analysis (Bucholz & Davis, 2015). When it is buried or lodged in an object or item, the whole item is typically taken to the lab in order to investigate it – an aspect of investigations that is woefully missing from the video (Bucholz & Davis, 2015). The collection of these materials is done very carefully, avoiding paper and glass containers to avoid perforation or commingling of broken glass with a glass container (Bucholz & Davis, 2015). The careful collection of these fragments aids in the glass analysis performed by CSI technicians, as it prevents contamination and preserves the integrity of the trace evidence as much as possible.
3. How can comparison of glass fragments help in CSI?
The comparison of glass fragments can be an incredible boon in CSI investigations. As previously mentioned, examining the density and refractive index of glass fragments found at a crime scene can link them to the type of glass found in a car window or other glass object involved in a crime scene. For instance, if glass is broken in a crime scene, and glass fragments are found on the perpetrator, it is possible for this comparison to link those fragments to the window at a crime scene. This then contributes to the case against the perpetrator, whether it proves or disproves their presence at the crime scene. Glass, along with hair, fingernails and paint, is considered trace evidence, and is treated as such in CSI investigations (Bucholz and Davis, 2015).
The video itself repeats a lot of the same points mentioned in the previous prompt/video, and largely works in the abstract, offering an example of one way in which glass fragments can help in CSI investigations (the linking of a perpetrator to a crime through glass fragments caught in their clothes). However, it would be useful to learn more about the kinds of ways in which fragments could be caught in clothes, and what that means for a crime scene (Bertino and Bertino, 2009). Furthermore, it is necessary to learn the different ways in which this evidence is collected depending on how it is found (are source materials taken from the crime scene to compare with the fragments in question? If so, how are they transported and what care is taken to limit contamination of evidence?). However, these videos still serve as a fundamental starting point from which one can learn more about the role of glass analysis in CSI.
References
Bertino, A. J., & Bertino, P. N. (2009). Forensic science: Fundamentals & investigations. Mason, OH: South-Western Cengage Learning.
Bucholz, A., & Davis, A. (2015). Forensic studies: CSI for the nonscientist: from crime scene to
crime lab. LawTech Publishing Group.
