Hair & Fibers

Class vs. Individual Evidence Hair is considered class evidence unless DNA can be isolated from the root. Remember: Class evidence can only be connected to a group Individualized evidence can be connected to a unique source.

Locard’s principle When two objects come into contact, material is exchanged. How much material is transferred is affected by Intensity of contact Duration of contact Type of surfaces

Questions to ask about trace evidence (hair and fibers) 1. What is it? 2. Man-made or natural? 3. What is its source? 4. How common is it? 5. Can it be identified to a single source?

Equipment Stereomicroscope Compound microscope Phase contrast microscope Scanning electron microscope Comparison Microscope FTIR- Fourier Transform Infra Red Spectrophotometer GC- Gas chromatograph

Why is human hair useful in forensics? Sheds easily Clings to clothes Lasts for long periods of time Toxins (esp. heavy metals) are deposited in hair. You can estimate the time of poisoning based on the growth rate of hair) Case study: Robert Curley case from Wilkes-Barre

Human Hair scalp pubic eyebrow & eyelashes beard chest arm leg

Structure of Hair Follicle= pocket of cells where hair grows Cuticle Cortex Medulla

1. Cuticle- overlapping scales always point up the shaft of the hair 2. Cortex- internal body, pigments 3. Medulla- inner core Smaller in humans than in animals

Types of cuticles Coronal – common in mice, rats Spinous(petal) – triangular shape, found in cats - makes cat hair stick to other materials easily Imbricate (flat) – humans

Cortex Contains pigment of the hair

Medulla Types Solid or continuous Interrupted Fragmented

How to match hairs Consider: 1. color and width 2. medulla type 3. cuticle type 4. shape of hair in cross section

Hair in cross section Armpit ----- oval Beard ----- triangular Head ----- round Eyelashes and brows ----- taper

Sources of Animal Hair Living animal Pelt Wool sweater Often pet hair transferred during crime

Fibers Small, elongated pieces of material used to make: Cloth Carpet Paper Cardboard Rope String

Fibers Classification: a) Natural- animal hairs (wool) - excrement (silk) - plant (cotton) - mineral (asbestos) b) Man-made nylon polyester rayon

Fibers Sorted by: Color Fluorescence Thickness Water retention Cross-section FTIR Chromatography of dyes