Glass & Soil Review

What is the state of matter of glass at room temperature?

It is an amorphous solid.

The main compounds in glass are __________.

Silicon Oxides & Metal Oxides

What is the name of the glass that is made by passing the molten glass through rollers?

Ordinary or rolled glass

Window glass is (more/less) dense than water.

More dense

The two most important physical properties of glass used for identification are:

Density and refractive index

True or False Density is not homogeneous over sheet of glass

True

True or False, when glass shatters it is easy to reconstruct the original shape.

false

This type of glass involves a treatment where the glass is heated to 620oC and then cooled rapidly. What is the name of this glass?

Tempered or Safety Glass

Name the type of glass that is used for flat glass, container glass, and electric light bulbs.

Soda Lime Silicate

The fracture pattern of glass usually has __________ lines.

Conchoidal

This type of conchoidal line appears first when glass is fractured.

Radial

For a ______________ fracture, the perpendicular end, faces the surface on which the force originated.

concentric

In a forensic laboratory, a technique frequently used to determine the density of glass involves the use of ___________

Density – Gradient tubes

Stress marks on the edge of a radial crack near the point of impact are ___________ to the side on which the force was applied.

parallel

True or False A crater-shaped hole is narrower on the side where the projectile entered the glass.

True

True or False – It is easy to determine from the size and shape of a hole in glass, whether to was made by a bullet or some other projectile.

False

A piece of window glass is submerged in vegetable oil A piece of window glass is submerged in vegetable oil. The outline of the glass is visible. When light is shown behind the glass, a bright halo appears near the border of the glass. This bright halo is called a _________.

Becke line

________ glass has a layer of plastic between two pieces of ordinary window glass.

Laminate or laminated

Name at least one out of three common problems associated with glass analysis (glass comparisons)

Find and measure properties Associate one glass fragment with another Minimize or eliminate other sources

The bending of light as it travels through one medium into another is known as ________.

Refraction

As light goes from the air into a liquid sample, the bending of light is due to a(n) ___________ in velocity of the light.

decrease

At 25oC the refractive index of water is 1. 333 At 25oC the refractive index of water is 1.333. This means that light travels 1.333x __________ in a vacuum than in water.

Faster

______________ solids Refract a beam of light in two different light-ray components (wavelengths) Results in double refraction

Crystalline

The numerical difference between these the two refractive indices of a crystalline solid is known as ________________.

Birefringence

This is an example of.. . . . . .

Birefringence

Technique used to determine the refractive index of a glass sample is known as the _____________ method.

Immersion

As the velocity of a fast moving projectile decreases, the irregularity of hole and cracks ____________.

increase

Exhibit (a) only shows a __________ fracture

Radial

Glass Collection True or False All broken glass at a crime scene must be collected, regardless of the size.

FALSE Know ALL of these steps for Glass collection Collect all glass found for piecing Submit all glass evidence found in the possession of the suspect Collect only a representative sample of broken glass remaining at the crime scene

True or False Once collected glass should be wrapped up in paper to prevent further damage.

False, Packaged in solid containers to avoid further breakage

Soil Collection Standard/reference soils should be taken from the crime scene at various intervals within a ______-yard radius of the crime scene. This will be used as a comparison to questioned soil.

100

Soil is a mixture of _______ and _________ material.

Soil is a mixture of organic and inorganic material.

An example of 100% inorganic soil is _________while an example of a nearly 100% organic soil would is ________.

An example of 100% inorganic soil is sand while an example of a nearly 100% organic soil would is peat.

The inorganic part of soil is ________.

minerals

The organic part of soil is known as _______ which is made up of __________________.

Humas decayed plant and animal material

The forensic definition of soil includes many things, including:

Bits of grass 9. Seeds Cinders 10. Animal matter Asphalt 11. Spores paint metals concrete Bricks Vegetation

List the five major factors that influence a soil’s composition.

Climate Parent material Living organisms Topography Time

True or False Soil is class evidence - cannot be individualized to a particular location

True

True or False There is no classification system for soils

True – only guidelines

True or False Soils can be easily transported

True – which makes it excellent trace evidence.

True or False Soils within a few meters horizontally or vertically differ

True

True or False After removing the first 2- 3 inches of top soil, a forensic soil analyst can tell if a body has been buried below.

True