CSI of Glass and Light
How the analysis of glass is used in CSI
Glass is often encountered in criminal investigations and hence is instrumental evidence. Analysis of glass comes about when during a break, glass is broken. The fragments of glass will be scattered in the coven of the perpetrator. Perhaps, when the glass fragments are taken to the crime lab, they will hopefully be linked by the crime laboratory technician to the broken glass at the scene. This link can be established by looking into the various properties of the glass, such as density and refractive index. When glass is broken, small and sharp pieces scatters over a wide area. Large pieces are usually found around the original location of the glass plane and in the direction of the blow. Also, in the direction of the blow, small shards can be thrown up to 10 ft. from the pane. Hundreds of shards are often inevitably caught in the clothing or hair of the person who broke the glass in case this was done by a violent blow.
Different kinds of glass studied in CSI
There are three main types of glass usually encountered in a crime laboratory. The soda lime, bottle glass or ordinary window glass is the most common glass usually found in the crime scene. When heated to a temperature of more than 650 degrees, the soda-lime glass starts to soften. This can prove useful in investigation of fires like in a case where the windows of a building are found to be deformed after a fire. The second type of glass is the laminated glass. This glass consists of two layers of soda lime glass sandwiched between a plastic medium. This gives the glass its strength and hence is used in the windshields. The third type of glass likely to be found in a crime scene is tempered glass. It is meant to withstand fracturing and hence does not shatter into pieces when it breaks.. As a result, the impacts on the car do not cause dice to cause jugged edges. The probability of finding glass evidence on the perpetrator, however, decreases over time since the fragments of glass caught in his or her clothes and hair begin to fall off within the first hour. The rate of falling will depend on the type of cloth the perpetrator is wearing at that particular time.
How comparison of glass fragments can help in CSI
Glass fragments in a crime scene help to solve hit and run. glass is typically used to link a perpetrator to a crime. For example, a crime scene may occur with a breaking of glass. As a result, a piece or some pieces of glass may be found in the procession of a perpetrator or suspect. The crime laboratory will therefore, attempt to pair those pieces of glass to the broken window at a crime scene. This comparison is typically carried out by looking into the characteristics of glass such as density and refractive index. The results are matched or compared to one another. Besides, the non-optical properties can be used to make this comparison. This include the surface texture, curvature and special treatment of the glass fragments.
How comparison of glass fractures helps in CSI
Glass fragments can be studied from a point of view of making and determination as to the direction of impact. For example, if a bullet travels through a glass window, sometimes it is important to try to understand what direction that bullet came. It is essential to determine if the bullet was fired in the home for example, or outside the home or if it was a close shot of it was shot from a distance. This will help the forensic to narrow down the perpetrators. Besides, it can be critical in reconstructing the crime scene. Also, this analysis allows forensic analysts to make some sort of determinations. The first thing to check for if all the fractures of a glass are present is the hole made by the projectile or the load. This can be a bullet, harmer or anything with a great tensile strength and the exit side is usually wider.
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