If a window or glass object is broken or shattered by a projectile, such as a bullet, the breakage pattern can be analyzed to possibly determine the angle of trajectory of the projectile, shedding more light on the crime, such as where the suspect was when the gun was fired.
What is glass in forensic science?
A forensic glass analysis is typically a comparison of two or more glass fragments in an attempt to determine if they originated from different sources. Less frequently, it is a question of determination of end use, or glass provenance.
How Can glass be used as evidence?
Glass – Glass can be used to gather evidence, for example collecting fingerprints or blood from a broken window; however, glass also has a place in the trace evidence section. … Gathering glass fragments from a crime scene can be valuable in determining end-use or connecting people and objects to places.
How is glass collected at a crime scene?
The glass should be placed in a sealed paper bindle or a folded and sealed paper or plastic bag, depending on size. Large pieces of glass with sharp edges should be put into sealed containers (such as cardboard boxes) in which they will not cut their way through.
What are the 2 types of glass fractures cracks?
When a projectile i.e. a bullet or rock hits the glass, it will form two distinct types of fractures: Radial and Concentric. There is another terminology that is known as cone fracture, observed to be caused by a penetration of the high velocity projectile such as a bullet.
Why is glass important in forensic science?
Broken or shattered glass found at a crime scene is an important piece of forensic evidence. … Using proper collection and preservation techniques when taking samples of glass fragments from a crime scene is crucial in order to avoid altering the evidence or missing important information.
What are the 4 types of glass?
There are four main types or strengths of glass:
- Annealed Glass. Annealed glass is a basic product formed from the annealing stage of the float process. …
- Heat Strengthened Glass. Heat Strengthened Glass is semi tempered or semi toughened glass. …
- Tempered or Toughened Glass. …
- Laminated Glass.
What is the 3R rule for glass fractures?
The 3R rule states that Radial cracks form a Right angle on the Reverse side of the force. This rule enables an examiner to determine readily the side on which a window or pane of glass was broken.
Is Broken Glass Class evidence?
Glass can be found as individual characteristic in cases where significant fitting of two glass fragments. … It is class evidence most of the time because without two fitting glass fragments, the glass can be identified but not linked to a specific object.
What are 5 ways of collecting hair evidence?
The most common methods used to collect hair and fiber evidence include the following:
- Visual collection. On some surfaces, hairs and fibers can be seen with the naked eye. …
- Tape lifting. Trace tapes are available for the collection of trace hair and fiber evidence. …
Who collects evidence at a crime scene?
A crime scene is any location that may be associated with a committed crime. Crime scenes contain physical evidence that is pertinent to a criminal investigation. This evidence is collected by crime scene investigators (CSIs) and law enforcement.
Where is glass evidence stored?
Place small glass fragments in paper bindles, then in coin envelopes, pill boxes, or film cans which can be marked and completely sealed. Place large glass fragments in boxes. Separate individual pieces with cotton or tissue to prevent breakage and damaged edges during shipment.
What is radial crack?
When enough force is applied to break this surface tension the entire pane of glass fractures into thousands of small pieces (dicing). … Terminology – • Radial cracks are fractures extending outward from the point of impact.
What 2 characteristics do high velocity bullets leave in glass?
Higher-velocity bullets will leave a very neat hole. A gun held close to the pane of glass (again, like a human body) will completely shatter it, because the hot gases from the muzzle of the gun escape rapidly and with great pressure. A pane of glass broken with a large stone will look the same.”
What are stress marks in glass?
Stress marks, seen on a cross section of a glass fracture, 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.