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.
What must a forensic scientist evaluate when examining glass fragments quizlet?
To compare glass fragments, a forensic scientist evaluates two important physical properties: density and refractive index . Flotation Method- the density of the liquid is carefully adjusted by the addition of small amounts of an appropriate liquid until the glass chip remains suspended in the liquid medium.
How do forensic scientists analyze glass?
Forensic glass samples can be analyzed by comparing the refractive index of the sample to that of the possible source . Examination of samples under a regular microscope or a scanning electron microscope can give detailed information about the sample’s physical and chemical characteristics.
What evidence can be found on glass fragments?
Trace evidence can be found at a crime scene in a number of different forms, including hairs and fibers, glass, or soil. Glass analysis includes determining the type of glass based on glass fragments. However, the entire fractured pane or window can be helpful when determining direction and sequence of force.
Which method is best for determining the origin of glass fragments?
The flotation and immersion methods are best used to determine a glass fragment’s density and refractive index, respectively. The latter involves immersing a glass particle in a liquid medium whose refractive index is verified unit it is equal to that of glass particle.
What is the importance of photos taken at least 2 opposite corners?
PHOTOGRAPHING THE EXTERIOR. The exterior of the building should be photographed from all sides or at least two opposite corners to show the overall degree of fire damage and the locations of the various entrances and windows .
What is the 3R rule forensics?
This is the forensic scientists’ [3R] rule— radial cracks make right angles to the rear . In a concentric crack, it’s the opposite—the chonchoidal fractures DO make a right angle to the side the force came from. This can be vitally important in determining if something was a shoot-out or a shoot-in.
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 is the first step Forensic scientists must do to analyze evidence?
What is the first step forensic scientists must do to analyze evidence? Take measurements to identify the characteristics of the evidence.
Is hair biological or physical evidence?
Physical versus biological evidence
Forensic evidence can be divided into two basic categories: physical and biological. ... Biological evidence , on the other hand, includes organic things like blood, saliva, urine, semen, hair, and botanical materials, such as wood, plants, pollens and yes, Clarice, moth cocoons.
What is the right container for glass fragment?
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.
What type of evidence is glass class or individual?
victim or suspect with a scene or with each other; e.g., personal belongings. The large piece of glass fits exactly to the bottle; it is individual evidence. These fibers are class evidence ; there is no way to determine if they came from this garment.
Which method is used to determine a glass fragments refractive index?
The most commonly employed procedure for the determination of refractive index of small glass fragments appears to be the Becke method , although the oblique light technique is regarded as but slightly less sensitive.
What does GSR stand for?
What does the abbreviation GSR represent? Gunshot residue .
What physical properties are used most often to characterize glass particles?
What physical properties are used most often to characterize glass particles? Density and refractive index are used.
