Human hair analysis is of substantial importance in forensic sciences field. Hair is most commonly found evidence on crime scene and needs prime attention in solving a crime situation. Hair is a filamentous biomaterial that grows from follicles present in the dermis. Found exclusively in mammals, hair is one of the defining characters of mammalian class.

From hair one can determine:

  1. If the source is human or animal.
  2. Race (Sometime).
  3. Origin of location on source’s body.
  4. Whether the hair was forcibly removed.
  5. If the hair has been treated with chemicals.
  6. If drugs has been ingested.

 

Why is Hair Important?

  1. It easily transfers during physical contact.
  2. While it can be individualized, it can be matched to a reference and provide strong corroborative evidence.
  3. Good evidence since hair is resistant to chemical decomposition and retains its structural features.
  4. If the source is human or animal.
  5. Race (Sometime).
  6. Origin of location on source’s body.
  7. Whether the hair was forcibly removed.
  8. If the hair has been treated with chemicals.
  9. If drugs has been ingested.

 

Morphology of Hair:

The structure of hair consists of:

  1. Cuticle:
  • The outer layer is composed of overlapping scales.
  • Provides the hair with its structure and resistance to chemical decomposition.
  • The scales are formed from special hardened cells and have 3 basic patterns: Cornal, Spinous and Imbricate.
  • It can either be scanned with an electron microscope or casted using a soft medium.
  1. Cortex:
  • It consists of spindle shaped cortical cells running parallel to the length of hair.
  • The location of pigment granules are used in comparing hairs (the color, shape and distribution varies amongst individuals).
  1. Medulla:
  • It is collection of cells running through the center of the hair.
  • Measured with medullary index, represented as a fraction.
  • Medulla can vary amongst hairs from the same person.
  • Types of medulla includes: Continuous, Interrupted, Patterned, Fragmented, Solid and Absent.
  • Humans have cylindrical medulla and animals may have patterns.

Medullary Index: It is determined by measuring the diameter of the medulla and dividing it by the diameter of the hair.

Medullary Index (I) = Diameter of Medulla

Diameter of hair

  • Medullary Index for human hair is generally < 1/3.
  • And for animals it is > 1/3.

Collection of Hairs: When hairs from a suspect’s head are needed for analysis against hairs found at a crime scene, they are plucked directly from different areas of the person’s head–as well as taken from a comb. Likewise, when pubic hairs are collected from a suspect’s body, they are taken from several areas of the pubic region. In both cases, about 25 hair strands are collected for testing.

Examination of Hairs: When forensic scientists analyze hairs, they first determine if the hairs came from a human or an animal. If the hairs came from an animal, they then work to identify the species of the animal. If the hairs came from a human, forensic scientists compare the hairs found at a crime scene to the hairs taken from a suspect. This examination will determine if the suspect was indeed at the crime scene. DNA analysis can also be performed from hairs.

Importance of Animal Hairs: Although animal hairs found at a crime scene cannot be linked to an individual animal, knowing the species can go a long way toward putting a suspect at the scene of a crime. For example, dog hairs may be found at a crime scene but it is discovered that the victim does not own a dog. If the suspect owns the breed of dog that the hairs came from, this evidence strongly suggests that the suspect and victim had contact.