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  1 st 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  1 st 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 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  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