Unit 4: Hair evidence

polymer

monomer

secondary transfer

direct transfer

fiber

yarn

textile

monomer

direct evidence

circumstantial evidence

direct evidence

circumstantial evidence

It can link a suspect to a crime scene

It is always unique to one person

It cannot be contaminated

It is the easiest evidence to analyze

It is not possible to show with certainty that two hairs came from the same person or animal.

Hair can be used to rule out certain suspects or scenarios.

Hair can only corroborate other physical evidence if consistent with the rest of the evidence.

Hair is always unique to each individual.

Whether the hair is from a human or animal

The exact identity of the individual

The presence of drugs or heavy metals

The body region from which the hair came

When hair is transferred from one person to another directly

When hair is transferred from a source to another location via an intermediate object or person

When hair is analyzed for DNA evidence

When animal hair is mistaken for human hair

Cuticle

Cortex

Medulla

Follicle

Curly hair has a circular cross section.

Straight hair has a flattened cross section.

Texture can be coarse or fine.

Cross section influences the curl of the hair.

Head and pubic hair

Facial and body hair

Eyebrow and eyelash hair

Beard and mustache hair

Scissors (freshly cut)

Uncut

Razor

Clippers

Traces of chemicals remain in the hair

Hair becomes more brittle

Pigment granules are removed by bleaching

Hair becomes thicker

Pigment granules

Cross section shape

Appearance (straight, wavy, or curly)

All of the above

Using tweezers to pick up visible strands

Using tape lift to collect hairs

Placing hair in paper bindles

Washing the hair before storing