Forensic Science

Forensic Science

Hair Evidence: Microscopic Examination

Hair ShaftHair ShaftComposed of:

Cuticle—outside covering, made of overlapping scales

Cortex—inner layer made of keratin and embedded with pigment

Medulla—inside layer running down the center of the cortex

Composed of:

Cuticle—outside covering, made of overlapping scales

Cortex—inner layer made of keratin and embedded with pigment

Medulla—inside layer running down the center of the cortex

Medulla Medulla

The medulla is a central core of cells that may be present in the hair.

The medulla is a central core of cells that may be present in the hair.

Types???

What type of medulla?What type of medulla?

What type of medulla?What type of medulla?

What type of medulla?What type of medulla?

Medullary Index (MI)Medullary Index (MI)

MI = diameter of medulla diameter of hair shaft

MI = diameter of medulla diameter of hair shaft

DiameterDiameter

“Edge to edge” measurement Because this measurement is so

small, we must use RATIOS to calculate it.

“Edge to edge” measurement Because this measurement is so

small, we must use RATIOS to calculate it.

Hair TipHair Tip

“Distal end” of the hair Appearance can help to

pinpoint the origin of the hair.

“Distal end” of the hair Appearance can help to

pinpoint the origin of the hair.

Scissor Cut

Razor Cut

Broken Hair

Burned Hair

Scissor Cut

Razor Cut

Broken Hair

Burned Hair

Glass-Cut or Broken

Hair Tip

Worn Razor-Cut Tip

Glass-Cut or Broken

Hair Tip

Worn Razor-Cut Tip

Bulb or RootBulb or Root

“Proximal end” of the hair Appearance can help to

identify whether a violent crime occurred.

“Proximal end” of the hair Appearance can help to

identify whether a violent crime occurred.

Which was forcibly removed?

Which was forcibly removed?

Why the difference?Why the difference? Hair has three phases of growth:

Anagen – primary growth of hair Catagen – intermediate phase Telogen – hair ready to be pushed out of the head.

When hair falls out naturally, it is in the telogen phase. Hair in the telegen phase is only loosly attached to the follicle. The bulb appears unstretched and no follicular tissue clings to it.

Anagen hair is tightly bound to the follicle. When such hair is forcibly removed, it resists the force (causing it to stretch out). It also carries along with it the material it was clinging to.

Hair has three phases of growth: Anagen – primary growth of hair Catagen – intermediate phase Telogen – hair ready to be pushed out of the head.

When hair falls out naturally, it is in the telogen phase. Hair in the telegen phase is only loosly attached to the follicle. The bulb appears unstretched and no follicular tissue clings to it.

Anagen hair is tightly bound to the follicle. When such hair is forcibly removed, it resists the force (causing it to stretch out). It also carries along with it the material it was clinging to.

Hair Forensics: DNAHair Forensics: DNA

Often it is not possible to extract DNA fully, or there is not enough tissue present to conduct an examination.

Hairs with large roots and tissue are promising sources of nuclear DNA.

Often it is not possible to extract DNA fully, or there is not enough tissue present to conduct an examination.

Hairs with large roots and tissue are promising sources of nuclear DNA.

FluorescenceFluorescence

Term used to describe objects that glow under certain wavelengths of

light

Term used to describe objects that glow under certain wavelengths of

light

FluorescenceFluorescence

Caused by dyes, bleaches, and optical enhancers.

Chemically treated hair Fabrics

Caused by dyes, bleaches, and optical enhancers.

Chemically treated hair Fabrics

Hair CuticleHair CuticleThe cuticle is a translucent outer layer of the hair shaft consisting of scales that cover the shaft. Cuticular scales always point from the proximal end of the hair to the distal end of the hair.

The cuticle is a translucent outer layer of the hair shaft consisting of scales that cover the shaft. Cuticular scales always point from the proximal end of the hair to the distal end of the hair.

CuticleCuticleThere are three basic scale structures of a

cuticle:

There are three basic scale structures of a

cuticle:

coronal (crown-like)

spinous (petal-like)

imbricate (flattened)

To visualize a cuticle:To visualize a cuticle:

Paint clear fingernail polish on a glass slide.

When the polish begins to dry, place a hair on the polish.

When it is almost dry, lift off the hair and observe the scale imprints.

Paint clear fingernail polish on a glass slide.

When the polish begins to dry, place a hair on the polish.

When it is almost dry, lift off the hair and observe the scale imprints.

Time for you to look at hair microscopically!!Time for you to look at hair microscopically!!

Goal: to identify, describe, and compare (using proper descriptive terminology) hairs from different sources. You will look at different people’s hair, hair that has been chemically treated, and hair from

different parts of your body.