Words to Know Cuticle Cortex Medulla Anagen phase Catagen phase Telogen phase Follicular tag Trichology Melanin granules

Individualization of Hair

Unable to individualize a human hair to any single head or body through its Morphology Structural

characteristics Link hair DNA to

DNA of donor

Examination of Hair 1st step to examination of

hair starts with color and structure or morphology.

The presence of hair at a crime scene denotes physical contact between a victim and assalent that is usually violent in nature.

Hair Morphology Hair: appendage of skin that grows

out of an organ known as the hair follicle.

Withstands chemical decomposition and retains structural features.

Length of hair extends from its root, continues into the shaft, and terminates at the tip end.

Shaft is composed of three (3) layers: Cuticle Cortex Medulla

Pencil analogy

Cuticle The scale structure covering

the exterior of the hair. Formed by overlapping scales

that always point toward the tip end of each hair.

Scales: hardened and flattened specialized cells (keratin) that progress form the follicle. Used in species identification

Must make a cast of scales and view under microscope for examination.

Cortex The main body of the hair shaft Housed within the cuticle Made of spindle-shaped cortical

cells aligned in a regular array, parallel to the length of the hair.

Where hair gets its color – pigmented granules The spacing and distribution of these

granules are an important characteristic when comparing two hairs.

Melanocytes: give color to hair. Examined microscopically using

liquid medium and reflected light.

Medulla A cellular column running

through the center of the hair.

Predominant feature in animals occupying more than half the hairs diameter.

Humans medulla usually occupies 1/3 of hairs diameter.

Medullary index: measures the diameter of the medulla relative to the diameter of the hair shaft. Normally expressed as a fraction. 0-1

Medulla Cont’d

Vary from individual to individual and even hair to hair or may not exist at all.

Classified three (3) ways: Continuous Interrupted Fragmented

Human hair are usually fragmented or medulla are absent. Exception Mongoloid Race (East Asian, North Asian

or Native American decent) have continuous medulla

Animal medulla either continuous or interrupted

Medulla Cont’d

Shapes and patterns Cylindrical Pearl spherical

Root

Grows in 3 developmental phases: Anagen Catagen Telogen

Anagen (growth) Phase

Initial growth phase during which the hair follicle actively produces hair.

Growth may last up to 6 years Root has flame-shaped appearance. When pulled a follicular tag may be

present Translucent piece of tissue surrounding the

hair’s shaft near the root and contains the richest source of DNA associated with hair.

Important in individualizing hair.

Catagen (transition) Phase A transition stage

between the anagen and telogen phases of hair growth.

Last 2 – 3 weeks Root takes on an

elongated appearance.

Telogen (resting) Phase Final growth phase in

which hair naturally falls out of the skin.

Root takes on a club-shaped appearance.

After 2 to 6 months of hair growth, the hair will naturally shed.

Hair Types

Head Pubic Eybrow/Eyelash Beard/Mustache Body Axillary

hypertrichosis

Hair Identification and Comparison 1st must be determined as

human or animal Examine scale structure,

medullary index, and medullary shape for identification.

Hair comparison is collected from head and pubic area. 30-50 samples needed.

When comparing hair need to match:

color Length Diameter Color intensity of granules in

cortex. presence/absence of medulla shape of medulla distribution of medulla

Collection and Preservation

Hair reference samples must come from the same area of the body as questioned samples Head hairs Pubic hairs

30 -50 full length hairs Use tweezers or forceps and should be stored

in bottles with snap-on lids. Rape cases; use clean comb on pubic area to

remove any foreign hair present before victim is sampled. Comb should then be packaged as evidence.

All microscopic hair comparisons must be confirmed by DNA analysis.

Central Park Jogger Case