Hair Biology and Forensic Analysis

Ear and Lip Pattern Evidence

• Ear and lip patterns can be used to identify a person.
• Lip patterns contain grooves that can be unique to a person.
• Ear shape patterns can also be unique.
• These methods require demonstration of uniqueness and permanence.
• While studies show unique and unchanging patterns, scientific validation is needed.

Hair Analysis Introduction

• Hair and skin share an ectodermal origin.
• Hair interacts with the environment and leaves forensic evidence.
• Hair and fibers are durable and retain forensic value for years.
• Hair provides structural info (appearance) and chemical info (composition) regarding origin and underlying biochemical makeup
• Fibres, both natural and man-made, can also provide similar valuable information about their origin, composition, form, and usage.

Hair and Fur

• Hair grows from follicles in mammalian skin.
• Hair helps regulate body temperature by trapping air.
• Hair composition is roughly 80-90% protein (mostly keratin and melanin) and 8-15% water with trace lipids.
• Hair color varies due to melanin type and concentration.
• Darker Hair = More Melanin.
• Light colored hair = lower melanin.
• Gray hair lacks melanin.

Hair Structure

• Hair has a cuticle, cortex, and medulla.
• The cuticle is the outermost, scale-like layer.
• The cortex is beneath the cuticle and contains most of the hair's structure.
• The medulla is the innermost core (sometimes absent or minimal).
• The cuticle protects the cortex and helps regulate water penetration.
• The cuticle's pattern (coronal, spinous, or imbricate) is species-specific.
• The medulla can provide structural info.
• The hair follicle is living and is associated with sebaceous glands(which produce oils) and an arrector pili muscle.

Hair Treatment

• Hair color and styling can be easily altered.
• Permanent color changes require chemicals to penetrate the cuticle.
• Treatments can leave forensic evidence on the hair.
• The degree of cuticle damage can help determine how long ago a hair was treated.
• Traces of products, dyes, and chemical procedures can be determined.

Sex and Ancestry Differences

• Hair structure (shape, and diameter) can vary based on ancestry.
• Hair on the body can show different shapes in relation to ethnic variations
• Color and structure variation in scalp, face, pubic area, etc.

Fingernails

• Fingernails and toenails are keratin-based appendages.
• Nails are used in assault cases; or to find a possible criminal/victim.
• Forensic analysis of nails shows patterns and growth features that remain.