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Hair Sample Analysis (Crime Fighters: Station 4)

Hair samples found at a crime scene can be useful in an investigation. Besides identifying the colour of the hair sample, scientists can distinguish whether the hair has been treated or coloured, test for drugs and poisons that may have been ingested, and may even extract DNA to help positively identify the hair’s owner.

Premise: Hair Samples in the Bedroom
The bedrooms on the second floor were ransacked. It was clear that the perpetrator had spent the weekend at the cottage home. After surveying the rooms, police determined that the culprit had slept in the son’s bedroom. The police carefully searched the bedroom and found hair samples, which they sent to the lab to be processed.

Can your student detectives narrow down the suspect with the hair sample evidence?

Objectives

  • Carefully compare, analyze and record evidence (hair/fibre) to infer a likely suspect.

Materials

  • Per Student:
    1 Crime Fighter’s Case Book
    pencil

  • Per Station:
    Hair Samples Sheet with hair from suspects
    1 hair from the crime scene
    1 microscope and/or several magnifying glasses

Key Questions

  • What are identifying characteristics of hair strands?
  • Is length a good characteristic to examine? Is curliness?
  • Which characteristics are most likely to give you the best clues?
  • How do you know the hair was from the culprit, and not from one of the victims?
  • What are some potential problems with collecting hairs from a crime scene? HINT: When was it left?

What To Do

Preparation

  1. Collect a hair sample from each of the suspects (including the culprit) and tape it to the Hair Samples sheet provided or onto microscope slides.
  2. Collect another hair from the culprit and add it to the Hair Samples sheet in the “sample from the scene of the crime” area. Alternately, tape it to a labelled microscope slide.
  3. Set up a microscope or provide magnifying glasses for students.

Activity

  1. “Detectives” carefully examine and record notes about each of the hair samples provided, noting things like colour, length, texture, thickness, whether it is curly, straight, or wavy, and any other clues that may be provided by the hair.
  2. “Detectives” then compare the hair evidence gathered at the scene to each of the samples provided by the suspects and determine which suspect’s hair most closely matches the hair found at the scene of the crime.

Extensions

  • Provide samples of fibres from the suspects’ clothing and one fibre collected from the crime scene. Examine these fibres the same way you examined the hair samples.