Forensic Science

The refractive index refers to the ability of a substance to ___ light

Bend

Describe Concentric fractures

Concentric series of circles one inside the other sharing the same center.

why does a becke line form?

It appears because the refracted light becomes concentrated around the edges of the glass.

What's the difference between synthetic and natural fibers?

Synthetic is man-made and natural is nature made. Synthetic examples: Rayon, Polyester Natural examples: Cotton, silk

What's the Anagen Phase?

THE FIRST STAGE LAST THOUSAND DAYS, 80-90% OF ALL PEOPLES HAIR IS IN THE ANAGEN STAGE.

Silk is a natural fiber produced by the silkworm. How does the body of the silkworm produce silk?

They produce the fiber in their bodies and form it from a single strand that measures 1 to 2km

The period of active hair growth is called the ____stage

Anagen

What is melanin? (Think of the COLOR of the CORE of a MELON)

BITS OF PIGMENT FOUND IN THE CORTEX OF A HAIR

What are the five different types of weave patterns?

PLAIN, BASKET, SATIN, TWILL, and LENO.

What is the background on glass?

PREHISTORIC HUMANS USED OBSIDIAN A TYPE OF GLASS FORMED BY VOLCANOES, AS A CUTTING TOOL

Human hair has which type of cuticle?

Pigmented

Which part of a hair can be analyzed for DNA?

Root

Calculate the medullary index of a hair whose diameter is 110 microns wide and whose medulla measures 58 microns. Is this a human or animal hair?

Sb/110-52 this is an animals hair

Neutron activation analysis can check hair for the presence of (its an element)

Silver

What's the Medulla?

THE CENTRAL CORE OF A HAIR FIBER

What's the Telegan phase?

THIS IS THE LAST AND FINAL STAGE. DURING THIS STAGE THE HAIR IS EASILY LOST. THIS ACCOUNTS TO ABOUT 10 TO 18% OF ALL HAIRS.

what characteristics of cotton make it a great source of fiber for clothing

The fibers are easily woven and dyed

Which of the following observations are used to help identify a specific fiber? A. Smell of the burned fiber on contact with the flame B. des the fiber coil or melt C.Color and Structure of the residue after it burns D.All of the above

D. All of the above

Which of the following characteristics is found in typical Asian hair?

Dark medulla

What is The ratio of an object to its volume; expressed by ___ = mass/volume.

Density!

What's the Catagen phase?

FOLLOWS AS THE HAIR GROWS AND CHANGES OF PERHAPS TURNING GRAY. THIS STAGE ONLY ACCOUNTS OF 2% OF ALL HAIR GROWTH AND DEVELOPMENT.

How can you tell that silk has the ability to refract light?

How shiny it is!

Fibers collected as trace evidence are often considered to be class evidence and not individual evidence. For example, the presence of a white cotton fiber found on a suspect and found on a victim at a crime scene is not enough evidence to convict the suspect. Justify this statement.

In many cases, a fiber can be identified, but not connected to a specific person, rather just a certain group of fibers

What's Keratin?

THE HAIR SHAFT IS COMPOSED OF THE PROTEIN KERATIN. WHICH IS PORUDCED IN THE SKIN. KERATIN MAKES HAIR BOTH STRONG AND FLEXIBLE

What's the Cortex?

THE REGION OF A HAIR LOCATED OUTSIDE OF THE MEDULLA CONTAINING GRANULES OF PIGMENT

What's the cuticle?

THE TOUGH OUTER COVERING OF A HAIR COMPOSED OF A HAIR COMPOSED OF OVERLAPING SCALES.

A fiber is collected at a crime scene. When viewed under a compound microscope, what two traits would indicate that the fiber was a human hair and not a piece of fiber obtained from an article of clothing?

The presence of a cuticle, a medullary index of .33 or less

Fibers are an excellent source of trace evidence because ____.

They are easily transferred from victim to suspect.

The cuticle scales of the hair always point toward the?

Tip of hair

Which factors are used to calculate the medullary index of the hair?

Width of medulla and width of hair

A characteristic of natural fibers is that they ____.

Won't break/melt when exposed to light

Why is hair considered class evidence?

Without the cells attached it can only identify a certain amount of people

What's the neuron activation analysis?

A METHOD OF ANALYSIS THAT DETERMINES COMPOSITION OF ELEMENTS IN A SAMPLE

What is a becke line?

A halo like ring that appears around the edge of glass when submerged in different liquids

Although variations can occur, which of the following best describes northern Europe hair?

A yellowish tint to the hair

The substance added to glass that makes crystal glasses seem to sparkle is ____.

Aluminum

Describe three sources of natural fibers. Provide an example of each type of natural fiber.

Animals hair, fur, webbing, plants seeds and fruit, minerals and fiberglass

What are three kinds of glass that are often sold as pyrex or kimax glass?

LEADED GLASS OVENWARE AND LABORATORY GLASSWARE

The hair shaft is composed of the cuticle, cortex, and ____.

Medulla

Mineral fibers such as asbestos are very durable. These fibers are used in all of the following except?

Natural fibers

Natural fibers can be harvested from ___, ____, and ___.

Plants, Animals, and minerals

Describe a radial line

Radial lines originating from point of impact and extending to edge of glass.

Will a radial fracture happen first, or a concentric?

Radial will form first followed by concentric because when an object hits the glass, the side opposite the impact is under compression which causes it to become weaker, and the weaker side will always break first.

Contrast radial and concentric when talking about force/impact

Radial- opposite the side of force or impact Concentric-same side as force or impact