Forensics Quiz

anagen stage

- Active growing stage of hair (cells rapidly dividing and depositing materials within the hair) - lasts approx. 1000 days - 80-90% of human hair is in this stage

catagen stage

- brief transitional stage of hair growth when all cell division stops - follicle recedes as the blood supply is reduced - 2% of all hair growth/development

animal hair v. human hair

- differ in pattern of pigmentation, medullary index, and cuticle type - medulla is proportionally thicker than in humans - medullary index > or equal to 0.5, it is animal hair - medullary index < or equal to 0.33, it is human hair

European hair

- generally straight or wavy - small and evenly distributed pigment granules - cross section: oval or round of moderate diameter with minimal variation - color may be blond, black, red, or brown

why is bleached/dyed hair easy to identify?

- it lacks pigment in the cortex and cuticle - changes color of hair shaft and gives it easily recognizable painted appearance - if an entire hair is recovered, experts can discover when the hair was last color-treated

African hair

- kinky, curly, or coiled; shaft may be buckled - pigment granules: densely distributed, clumped, may differ in size and shape - cross section: flattened with moderate to small diameter and considerable variation

Asian hair

- straight - densely distributed pigments - cross section: round with large diameter - shaft tends to be coarse and straight; thick cuticle; continuous medulla; color black

telogen stage

- the final or resting phase in the hair growth cycle - follicle becomes dormant - 10-18% - at the end of this stage, the blood supply reconnects to the follicle and the anagen stage begins again

phase contrast microscopy

- uses special objective lens and special condenser with a compound microscope - focuses light that passes through objects at different angles

six types of hair on human body

1. head 2. eyebrows and eyelashes 3. beard and mustache 4. underarm 5. body 6. pubic

how fast does human hair grow?

1.3 cm per month (0.44 mm per day)

Gas Chromatography

Test on hair that can identify and quantify drugs, toxins, heavy metals, and even assess nutritional deficiencies.

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

Dark medulla

what are the three ancestrally significant groups associated with hair?

European, Asian, and African

T/F Hair is composed mostly of protein called cellulose

False

T/F To determine blood type, Luminol is added to blood

False

T/F all hairs on the head of a person are identical

False

Secondary transfer (Locard's Principle of Exchange)

The transfer of evidence such as a fiber from a source (for example, a carpet) to a person (suspect), and then to another person (victim).

T/F Hair can provide clues about someone's ancestry

True

T/F blood spatter on a wall in a series of rising and falling arcs is often caused by a severed artery

True

T/F blood-typing evidence is now used more to exclude a suspect than to identify a suspect

True

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

True (gives only color of hair)

Wipe blood-spatter stains

a pattern that is created from an object moving through a partly dried bloodstain

isotope analysis

a technique that helps provide a timeline of a person's movements through a strand of hair

What can hair be used to determine?

diet, drug habits, and geographic history

how to find number of months since drug use?

divide length of hair at which toxin was found by 1.3

how can we estimate when hair was last colored?

dividing hair length by 1.3

imbricate

flattened, overlapping scales commonly found in human and in many animal hairs

Which part(s) of a hair can be analyzed for nuclear DNA?

follicle

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

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

Human hair has which type of cuticle?

imbricate

cortex

largest part of the hair shaft; contains the most melanin granules that give the hair its color

electron microscope

microscope that forms an image by focusing beams of electrons onto a specimen

how is hair first examined?

microscopically

Type O blood

no antigens but does have A and B antibodies

What is the most likely result of hair bleaching?

oxidized hair and damaged DNA

Spine and satellite

spine is sharp, splendor, and often-pointed projection, while blood satellites are small secondary drops

Although variations can occur, what best describes European hair?

straight or wavy with evenly distributed granules

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

telogen

Blood Adhesion

the attraction between molecules of different substances

Blood cohesion

the attraction between molecules of the same substance

medulla

the central core of a hair

Type AB+ blood

Contains the A antigen, B antigen, and the Rh factor on the surface of RBCs

fluorescence microscopy

uses a fluorescent dye that emits fluorescence when illuminated with ultraviolet radiation; indicates dye on hair

how many hairs are usually collected from a suspect/victim's head?

50 (to prevent inconsistencies)

The Structure of Human Hair

A hair consists of two parts: a follicle and a shaft. The follicle, a club-shaped structure, contains cells with DNA and nutrients. The hair shaft is composed of the protein keratin, which is very strong and resistant to decomposition (making it very useful to forensic scientists).

What is needed for hair to be evidence?

A hair must have the follicle and its nuclear DNA, or genetic material in its nucleus, or it cannot provide individual evidence. Mitochondrial DNA (mtDNA), which is inherited from the mother, can reveal some of suspect's or victim's family relationships. Physical examination of hair, however, can provide class evidence.

The hair shaft

Made up of three layers: an inner medulla, a cortex, and an outer cuticle

Swipe blood-spatter stains

the result of a bloody object in motion that comes into contact with another clean surface

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

the width of the medulla and width of the hair

What is microscopic hair analysis used for?

to exclude a suspect

cuticle

transparent outer layer of the hair shaft; made of scales that overlap one another and protect the inner layers of the hair