-The change in the refractive index value for tempered glass upon annealing is significantly greater when compared to non-temperedglass and thus serves as a point of distinction Glass Fractures Glass bends in response to any force exerted on any one of its surfaces; when the limit of its elasticity is reached, the glass fractures. -Fractured window glass reveals information that can be related to the forced and direction of an impact; such knowledge may be useful for reconstructing events at a crime scene investigation Radial Fracture is a crack in a glass that extends outward like the spoke ofa wheel from the point at which the glass was struck (radiating lines)Concentric fracture is a crack in a glass that forms a rough circle around the point of impact. (circular lines)
Subscribe to view the full document.
The presence of gunpowder deposits on the shattered glass fragments points to damage caused by a firearm. -When it penetrates glass, a high velocity projectile such as a bulletoften leaves a round, crater shaped hole surrounded by a nearly symmetrical pattern of radial and concentric cracks. -The hole is inevitably wider on the exit side, and hence examining it is an important step in determining the direction of impact. However, as the velocity of the penetrating projectile decreases, the irregularity of the shape of the hole and of its surrounding cracks increase,so that at some point the hole shape will not help determine the direction of impact -Determining the radial and concentric fracture lines will help determine the direction of impact When a force pushes on one side of a pane of glass, the elasticity of the glass permits it to bend in the direction of the force applied. -Once the elastic limit is exceeded, the glass begins to crack Stress marks are shaped like arches that are perpendicular to one glass surface and curved nearly parallel to the opposite surface. The importance of stress marks stems from the observation that the perpendicular edge always faces the surface on which the crack originated. -The stress marks on the edge of a radial crack near the point of impact -The perpendicular end is always found opposite the side from which the force of impact was applied-Concentric fracture, the perpendicular end always faces the surface on which the force originated 3R rule- Radial cracks form a right angle on the Reverse side of the force. It is frequently possible to determine the sequence of impact by observingthe existing fracture lines and their points of termination. A fracture always terminates at an existing line of fracture. Collection and Preservation of Glass Evidence Collect all the glass found at the crime scene. The evidence may ultimately prove invaluable in placing a suspect vehicle at the accident scene by matching the fragments with glass remaining in the headlight orreflector shell of the suspect vehicle -Examining the headlight’s filaments ma reveal whether an automobile’s headlights were on or off before the impact Evidence collector must submit all glass evidence found in the possession of the suspect along with a sample of broken glass remaining glass at the
As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.
Temple University Fox School of Business ‘17, Course Hero Intern
I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.
University of Pennsylvania ‘17, Course Hero Intern
The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.
Tulane University ‘16, Course Hero Intern
Ask Expert Tutors
You can ask 0 bonus questions
You can ask 0 questions (0 expire soon)
You can ask 0 questions
(will expire )