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.
How do you collect evidence from glass?
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. Seal and mark the box containing them.
What is glass Evidence separated by?
Glass examiners compare samples of glass found on suspects or found at the scene of a crime with a suspected source of known origin by measuring the physical and optical properties of color, thickness, density, and refractive index. In most cases, these have been good methods for differentiation between glasses.
How can glass fragments help in the crime scene investigation?
Fragments of glass from headlights at a hit-and-run scene can leave clues about the unknown vehicle. Also, glass fragments can help police determine which direction the first bullet was fired through the glass. These clues can be gathered through the analysis of even the smallest fragments of glass.
What are the method used for matching of glass evidence?
(g/cm3 (solids); g/mL (liquids)) • One method of matching glass fragments is by a density comparison. Each type of glass has a density that is specific to that glass. If two samples of glass can be differentiated by density, they could not have originated from the same source.
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. …
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.
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.
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.
Why is glass class evidence?
Very small glass fragments would not fit together well, some fragments would probably not be found at all. This would make it more difficult to put the pieces together and match to the rest of the bottle; so this is class evidence.
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.
Is glass trace or physical 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. Broken glass fragments can be very small and lodge in shoes, clothing, hair or skin.
What are the two most often used methods of glass analysis?
The flotation and immersion methods are best used to determine a glass fragment’s density and refractive index, respectively.
What property is used to identify glass and match it to glass at a crime scene?
Refractive index is the most commonly measured property in the forensic examination of glass fragments (Koons et al. 2002), because: Precise refractive indices can be measured rapidly on the small fragments typically found in casework.
How do you collect hair evidence?
An investigator can collect hairs they observe visually (with tweezers or by hand), and they can also use clear tape to lift non-visible hair from a variety of surfaces, such as clothing. Other methods of hair sample collection include combing and clipping methods.