Hairs and Fibers Evidence in Forensics

Introduction

• Overview of hair and fiber evidence in forensic science.
• Importance of understanding different parts of hair and types of fibers.

Structure of Hair

• Hair is composed of keratin, a vital protein.
• Produced from hair follicles, which can shrink leading to baldness.
• Hair color is influenced by pigments and genetic factors.

Key Parts of Hair

1. Cuticle (Outer Layer)

   • Composed of overlapping scales.
   • Different patterns: coronal, spinous, and imbricate.
   • Useful for differentiating species but not for specific identification.

2. Cortex (Middle Layer)

   • Contains pigments and determines color.
   • Most important for identifying a specific individual.
   • Variation in thickness, color, and texture among individuals.

3. Medulla (Inner Core)

   • Central part of the hair.
   • Important for species differentiation but not for individual identification.
   • May vary in thickness or be absent.

DNA and Root of Hair

• DNA is present only if the root is intact.
• Root provides clues about how hair was removed (pulled or shed).

Significance of Hair Evidence

• Hair is considered class evidence when the root is absent.
• Humans shed approximately 100 hairs daily, which can be found at crime scenes.
• Analysis can determine:
  • Human vs. animal hair
  • Possible race of the individual
  • Body location (head, arms)
  • Chemical treatments (dyeing, perming)
  • History of drug use based on hair length.

Microscopic Differences between Human and Animal Hair

• Medulla:
  • Humans: less than one-third width.
  • Animals: larger proportion of the hair.
• Pigmentation:
  • Humans: more spread out.
  • Animals: closer to the medulla.
• Cuticle Patterns:
  • Humans: typically imbricate.
  • Animals: can show all three patterns.

Fibers as Trace Evidence

• Fibers can also be found at crime scenes and are categorized as class evidence.
• Two types of fibers:
  1. Natural Fibers:
     • Derived from plants or animals (e.g., silk, cotton, wool).
  2. Synthetic Fibers:
     • Man-made (e.g., nylon, polyester).

Comparison of Natural and Synthetic Fibers

• Natural fibers appear less organized under a microscope.
• Synthetic fibers have a perfect structure due to man-made processes.
• Delustrants: Added to synthetic fibers to reduce shine.

Analyzing Fibers

• Methods for differentiating fibers:
  • Microscopic examination
  • Burning tests
  • Chemical tests (odor, residue)
  • Dye analysis
  • Density measurement.

Conclusion

• Hair and fibers are valuable forms of evidence in forensic investigations, providing insight into various aspects of a crime.