Trace Evidence - Hair

Hair is made of ___?

Keratin

What is the structure of hair?

• Cuticle (outside)

• Cortex (main)

• Medulla (middle)

Properties of the Cuticle

• Made of overlapping scales that form the protective layer of hair

• Scales point towards the distal end of the hair

• Has a high cystine concentration

Coronal Scale Pattern

Spinous Scale Pattern

Imbricate Scale Pattern

Pattern found in human hair.

Pigment is contained in the ___?

Cortex

Eumelanin

Brownish-black pigment

Pheomelanin

Reddish-yellow pigment

Properties of the Medulla

• Located in the center of the hair, and runs down lengthwise

• Made of air-filled vacuoles

• NOT present in all hair

• Can be classified as:

  • Fragmentary/trace

  • Discontinuous/broken

  • Continuous

Uniserial ladder structured medulla

Multi-serial ladder structured medulla

Cellular (vacuolated) structured medulla

Lattice structured medulla

What are the three phases of hair growth?

• Anagen

• Catagen

• Telogen

Anagen Phase Characteristics

• Active growth phase

• Follicle extends to greatest depth

• Roots will be soft and formless. May have tissue and pigment adhering to them

• If a found hair root is in this phase, it is a good indication that the hair has been pulled out.

• 85% - 95% of human scalp hairs in this phase.

  • Lasts 2 - 6 years

Catagen Phase Characteristics

• Hair will start to form a keratinized root bulb, with a bulbous appearance

• Melanin production ceases

• 1% - 2% of hair in this phase

  • Lasts several weeks

Telogen Phase Characteristics

• The resting phase of the hair

• Root is enlarged and bulbous in humans

• Hairs naturally shed in this phase (exogen)

• 10% - 15% of hairs in this phase

  • Period lasts a few months

How fast does hair grow?

On average of 1cm a month

Can you determine age of an individual based on microscopical examination of the hair?

Yes, to some extent.

• 0 - 3 years will have hair that increases in cross section size, slowing at age 3, but continuing into adolescence.

  • Ratio of medulla’s size to hair diameter (medullary index). Tends to increase in advancing age.

Pigment is produced in gray hair; T/F

False

Why must a known sample of hair be collected?

To perform microscopic hair comparison.

• Known samples are typically pulled from the scalp and pubic regions

• Collected by both combing and plucking

• Important to collect 25 hairs from head/pubic region.

  • If from head: 5 from top, front, back, and both sides

• Important to collect complete hairs (with roots!)

How many types of human hair are there?

Three

• Lanugo Hair

• Vellus Hair

• Terminal Hair

Lanugo Hair Characteristics

Present before or shortly after birth. Fine, with no medulla (unmedullated) or pigment.

Vellus Hair Characteristics

Fine, no medulla (unmedullated), no pigment. Present on all skin surfaces, save for friction ridge skin.

Terminal Hair Characteristics

Primary terminal hairs include head, eyebrow, eyelash hairs.

Secondary terminal hairs include pubic, axilla, and beard hairs. Resulted from vellus hairs becoming terminal hairs.

How many types of animal hairs are there?

Three:

• Guard hair (overhairs)

• Fur hairs (underhairs)

• Vibrissa (whiskers)

Guard Hairs (Overhairs)

• Longer and stiffer than other hairs.

  • Have the morphological characteristics that allow them to be classified as that particular animal.

Fur Hairs (Underhairs)

Fine and undulating hairs which mostly lack morphological characteristics.

Vibrissa (whiskers)

Long, stiff hairs that are less likely to be encountered in forensic casework.

Is the cuticle colored?

Depends.

Unless the hair has been dyed, apart from the natural yellowish color of keratin, the cuticle will not be colored.

What are ovoid bodies?

Large agglomerations of pigments found in the cortex

Characteristics of the Medulla

• Air Filled

• Not present in all hairs

• Appears black in transmitted light.

• Appears white in reflected light.

• No more than 1/3 of the hair diameter and are not structured. (amorphous)

Animal hairs show variation in diameter. What is the shield?

The thicker part of the hair.

Animal hairs show variation in diameter. What is the shaft?

The thinner part of the hair.

Banding

Abrupt pigment changes in animal hair.

Cortical Fusi

Small, elongated air spaces in the cortex.

Animal Hair Medulla Characteristics

• Wide/structured medullas

• Have pigment in the medulla.

  • will be black in transmitted light

Anagen hair characteristics

• Roots not fully keratinized

• Pigmentation fully extends to roots

• Exposure to air will cause roots to harden

• Expect to see a follicular sheath

• Indication that the hair was pulled

• Root may also be sticky

Telogen hair characteristics

• will be highly keratinized

• Shaft proximal to root will lack pigment, but may have cortical fusi

• Human hairs form into a club shaped root

• Will lack a medulla

Catagen hair characteristics

• root bulb will be forming and starting to keratinize

• Some root sheath may be present

Postmortem changes to hair

Hairs may develop a band in the shaft proximal to an incompletely keratinized root of a hair that is still attached to a deceased individual.