Hair Test Review

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?

.527 microns = ANIMAL HAIR

{TRUE OR FALSE} 1. The shaft of the hair is considered class evidence in a trial 2. Hair is composed mostly of a protein called cellulose 3. All hairs on the head of a person are identical 4. Hair can provide clues about someone's ancestry

1. T 2. F, keratin 3. F 4. T

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 animal. Describe two ways that animal hair differs from human hair.

Animal hairs a greater medullary index + can have a diff. cuticle pattern

Catagen Phase

Intermediate period of hair growth, the hair follicles prepare themselves for next phase + lasts about 1-2 weeks = Intermediate Stage {deeper portions of hair follicles start to collapse

List the features which are examined when observing a hair under a microscope.

Medulla, Coretx + Cuticle

Fragmented Medullary Index

Not Evenly Spaced

Absent

Nothing in between

Which of the following is most likely a result of hair bleaching?

Oxidized hair and Damaged DNA

Telogen Phase

Resting and shedding period of the hair cycle, lasts about 3-4 months = Resting/Shedding Stage {older hairs finished their life and will fall out causing newer hairs to grow}

Continuous Medullary Index

Straight Line

Although variations can occur, which of the following best described European hair:

Straight or wavy with evenly distributed granules

The period when hair is naturally shed is called the ___________ stage

Telogen

Microscopic hair analysis is...

used to exclude a suspect

Solid

Filled In

Which part{s} of a hair can be analyzed for nuclear DNA?

Follicle

Anagen Phase

Growth period of a hair follicle, this stage/phase lasts about 3-5 years = Growing Stage

Describe the structure of hair:

Hair grows from a FOLLICLE found in the skin. It is composed of an inner MEDULLA, surrounded by the CORTEX, and protected on the outside by the CUTICLE.

Two different hairs were found at a crime scene. One hair strand only provided class evidence, whereas the other hair strand provided both class and individual evidence. How is this possible?

Hair is considered class evidence when no source of DNA, such as follicle cells, is attached to the hair. Without DNA, hair can only be used as class evidence, to indicate color of hair and perhaps racial group. The hair providing class + individual evidence must have had follicle cells attached and therefore, DNA.

Where would an investigator look for control hairs in a missing person's case?

Have to have something to compare it to, not all hairs are identical. 50 hairs can be taken

DNA can be extracted from hair so why is hair found at a crime scene not normally used for DNA typing?

If you don't have root there is no nuclear DNA; mtDNA = only links mother's genetics, only used to exclude people + not consistent; only provides CLASS EVIDENCE

Human hair has which type of cuticle?

Imbricate

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

Width of medulla over width of hair

Is it possible to determine if a body hair was forcibly removed from the body?

YES, they have to look at the torn looking end

What is the main purpose for examining a hair found at the crime scene?

You can eliminate suspects, can't prove someone did the crime. CLASS EVIDENCE!

Animal hair can be distinguished from human hair because animal hair...

has a greater medullary index and more variation in the cuticle patterns

A woman with long hair is a suspect in a burglary case. At the crime scene, several long hairs were found attached to a broken lock of the safe. The police obtain a warrant and request a sample of 25 to 50 hairs from this woman. They tell the woman it is important that they pull the hairs from her head rather than to merely cut the hairs. The police suspect that the woman was stealing to help support a drug habit. 1. Why is it important that the police pull the hairs from her head rather than cut her hair? 2. Why is it necessary to obtain 25 to 50 hairs from this woman? 3. The woman denies that she is currently taking drugs and states that she stopped using drugs a year ago. Explain how the police can determine if the woman has been off drugs for over one year. 4. Suppose the hairs of the woman match the hairs found at the crime scene. Why does this not necessarily prove that she was the guilty party?

1. They need to pull the hair so they will have follicle tags on them = DNA analysis can be performed so it could lead to individual evidence 2. The more the better! Giving multiple hairs = more accurate picture of the woman's exposure to drugs + other toxins because the hairs of an individual vary 3. If the woman has been off drugs for over a year, traces of the drugs will appear in her hair after roughly 16 cm 4. If hairs at the crime scene do not contain DNA, they cannot be used to determine the identity of an individual. Even if they do not contain DNA, they only prove that she was at the scene, not that she was there at the time of the crime

What is the approximate growth rate for hair?

1.3 cm per month

Can you distinguish a hair that has been bleached or dyed from a natural hair? How?

Bleach = no pigment/absence of color Dye = filled in {as if it's painted} Natural = has pigment Cuticle + Cortex take the color of the dye

The shaft is composed of what three layers?

Cuticle, Medulla + Cortex

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

Dark Medulla

The medullary index measures what?

Diameter of medulla / Diameter of hair = Animal hair is ≥ .50 Human hair is ≤ .33

Hair can used to determine....

Diet, Drug Habits + Geographic History

Interrupted Medullary Index

Evenly Spaced

The cortex contains granules. What are these granules and what do they determine?

They give your hair color/pigment = melanin; the granules are melanin granules

Imbricate Scale Pattern

are commonly found in human hairs and many animal hairs

Spinous Scale Pattern

found at the proximal region of mink hairs and on the fur hairs of seals, cats, and some other animals & they are NEVER found in human hairs

Coronal Scale Pattern

found in the hairs of small rodents and bats but rarely in human hairs