hair analysis forensics science

Hair grows on average _________________ per month.

1/2 inch

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

58/110 = .53, most likely animal due to index being larger than .33

Neutron Activation Analysis can check hair for the presence of

Elements, Compounds, molecules

When taking hair samples from a suspect to match to hair found at a crime scene, why would forensics specialist need to take several samples from the suspect.

Hair can be different even on the same person head. So more samples would give a higher likelihood of making a match.

Describe the structure of hair, include proper terminology.

Hair grows from the follicle, composed of inner medulla, surrounded by cortex, and an outer cuticle layer.

Why is hair considered class evidence?

Hair is considered class evidence when no source of DNA (follicle) is attached to hair. Can only indicate groups that hair may belong to.

Crime-Scene Investigators collected hair from a dead person's body. One of the first things that needs to be established is if this hair is human or non-human. Describe two ways that animal hair differs from human hair.

Human and animal hair differs in medulla index, cuticle pattern, and possible pigmentation distribution.

The body of a woman was found in the woods. Some hair fibers found on the body were sent to the crime lab for analysis. The ends of the hair attached to the body were gray, but the tips of the hair showed that it had been dyed. The distance from the end of the follicle to the beginning of the dyed area measured 5.3 cm. The section of hair that was dyed measures 4.2 cm. If hair grows at a rate of 1.3 cm per month, how long ago did the woman dye her hair and approximately when did she die. Explain your answer.

Human hair grows about 1.3 cm per month. 5.3cm/1.3cm = 4.07 or about 4 months ago she dyed her hair. 5.3cm + 4.2cm = 9.5cm/1.3cm= 7.3 or about 71/2 months ago she died.

A large medullary index (greater than .5), generally indicates that a given hair sample is not from

a human

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

width of medulla and the width of the hair

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

round cross section of the cortex, black pigmentation

Racial or ethnic differences (class differences) can be seen by looking at the _______________________ of the hair?

cross section of cortex

What hair features would allow you to differentiate between human and animal hair. Human and animal hair differs in medulla index, cuticle pattern, and possible pigmentation distribution.

cuticle, medulla, medulla index, pigmentation location in the cortex.

All hairs on the head of a person are identical.

false

Which parts of the hair can be analyzed for DNA?

follicle

Medullary index = diameter of diameter of

hair medulla

Human hair has which types of cuticle?

imbricate

The hair shaft is composed of the cuticle, cortex, and ?

medulla

What hair features would allow you to differentiate between human hair?

medulla, color, texture

The most active growth phase of hair is _______________________________. On average this phase last up to ____________ to ________________ years.

anagen 3 to 5

Hair is composed of a protein called keratin.

true

The cortex may contain pigment granules

true

The shaft of the hair is considered class evidence in a trial

true