Forensic Biology - Hair Summary

Overview of Forensic Biology - Hair

Biological Functions of Hair
Hair acts as a protective barrier against foreign particles and aids in temperature regulation. It develops during fetal growth and originates from 'hair follicles'. Follicles begin to decline in number as humans age.

Anatomy of Hair
Hair consists of:

  • Sub-dermal Structure: The hair root within the follicle is the only living part, nourished by blood supply and glands that secrete sebum.

  • Epi-dermal Structure: The hair shaft is non-living, made of proteins like keratin (provides strength) and melanin (determines hair color).

Microscopic Structure
Hair has three layers:

  1. Cuticle: The outer layer, consisting of scale-like cells.

  2. Cortex: The thick, middle layer that provides strength and color.

  3. Medulla: The innermost layer, variably present, important in forensic analysis.

Functions of Hair
Hair protects against foreign substances, aids in gender identification, and can provide DNA for forensic analysis. Its properties vary across the body.

Transfer of Hair
Hair is significant evidence in forensic science for establishing relationships in crime scenes. Natural shedding leads to the collection of hair as evidence during investigations. Comparison microscopy aids in determining the origin and characteristics of hair, essential in linking suspects to crimes.

Persistence of Hair
Postmortem changes slow decomposition, making hair a critical component in determining the time of death. Evidence from hair can indicate the circumstances preceding death.

Biochemistry of Hair
Hair is primarily composed of keratin and melanin, determining color and properties. Genetic factors influence pigmentation, contributing to hair’s diversity.

Coloring and Bleaching
Procedures differ: Coloring deposits pigments on the cuticle while bleaching chemically lightens hair. Care is required post-treatment to maintain hair health.

Human vs. Animal Hair
Key differences include medullary index and scale patterns, useful for species identification in forensic analysis.

Hair Examination Techniques
Methods like microscopy and temporary mounts enable the study of hair structure and origin, crucial for forensic tasks.

Gender Identification
Modern techniques like barr body tests, which identify female cells, and Y-body tests for males, are utilized in hair analysis for gender determination.

Drug Analysis via Hair
Hair is also used for detecting drug use. Samples must be properly collected and processed using various laboratory techniques for analysis.