Chapter 14
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Paint as physical evidence is most frequently encountered in what types of crime?
Hit-and-run.
What can the PDQ database help determine about a vehicle when paint chips are recovered?
The make, model, and year of the vehicle.
What is paint composed of?
Paint is made of pigments, binder, and solvents.
What is the role of the electrocoat primer on cars?
: Provides corrosion resistance.
What is the role of the primer surfacer on cars?
Smooths out imperfections and enhances adhesion of the basecoat.
What is the role of the basecoat on cars?
Provides the color and aesthetic appeal of the vehicle.
What is the role of the clearcoat on cars?
Adds protection and a glossy finish.
Which property of paint imparts it with its most distinctive forensic characteristics?
The layer structure.
What is the main ingredient in ordinary glass?
Sand (silicon dioxide).
Where is tempered glass used?
In car side windows/for protection.
What does flotation determine about a particle of glass?
Its density.
Describe radial cracks in glass.
Cracks that extend outward from the point of impact.
Describe concentric cracks in glass.
Cracks that form in a circular pattern around the point of impact.
What are the two most important physical properties of glass for forensic comparisons?
Density and refractive index.
What does the larger opening of a crater-shaped hole in glass indicate?
The exit side of the projectile.
If broken glass cannot be physically pieced together, what characteristics should be compared?
Density and refractive index.
How is the refractive index of a medium determined?
By the ratio of the speed of light in a vacuum to the speed of light in the medium.
How should glass evidence be collected and packaged?
Collect all visible fragments. Package in rigid containers to avoid further breakage. Label each fragment by location.
How should paint chips be collected and packaged?
Use tweezers or a clean sheet of paper. Package in sealed containers (e.g., vials, paper folds).
How should soil evidence be collected and packaged?
Collect samples in airtight containers. Prevent cross-contamination by using separate containers.
How much soil is needed for comparison?
Approximately 1 to 2 tablespoons.
At what distance should various soil samples be collected?
Within a 100-yard radius of the crime scene.