demonstrations:hair_sample_analysis
Hair Sample Analysis
Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required
Categories: Cells and Microscopes, Forensics
Alternative titles: Forensic Hair Comparison
Summary
Students act as forensic scientists by examining hair samples collected from suspects and a crime scene. Using magnifying tools, they compare features such as color, thickness, and curliness to identify the most likely suspect.
Procedure
- Prepare a hair sample sheet with taped hairs from each suspect, along with one hair from the crime scene (the culprit’s).
- Optionally, mount hairs on labeled microscope slides for easier viewing.
- Set up microscopes or magnifying glasses at the station for closer inspection.
- Provide each student with a case book and pencil for recording observations.
- Have students examine each hair, noting color, length, texture, curliness, thickness, and other visible characteristics.
- Direct students to compare the crime scene hair to each suspect’s sample, identifying the closest match.
- Encourage students to explain their reasoning, highlighting which features led them to their conclusion.
Links
Forensic Hair Comparison Lab - Heidi Hisrich:
Forensic Science and Hair Analysis - Marysusan Noll:
📄 Hair Sample Analysis - Science World: https://www.scienceworld.ca/resource/hair-sample-analysis-crime-fighters-station-4/
Variations
- Provide fibers from suspects’ clothing along with one found at the crime scene and analyze them in the same way as hair samples.
- Use digital microscopes to capture and compare images of the hairs.
- Introduce hair samples treated with dye or heat damage to show how treatments alter microscopic appearance.
Safety Precautions
- Handle microscopes and magnifying glasses carefully to prevent damage.
- If cutting hairs for slides, use scissors safely and store them properly after use.
- Keep all samples sealed or taped securely to prevent contamination or loss.
- Wash hands after handling hair or fiber samples.
Questions to Consider
- What characteristics of hair are most useful for comparison? (Color, thickness, curliness, and texture provide stronger clues than length alone.)
- Why might length not be a reliable identifying characteristic? (Length can vary within an individual depending on when the hair was cut or shed.)
- How could dyed or treated hair affect the analysis? (It may mask natural color or damage the hair, making comparisons more difficult.)
- How can investigators be sure the hair came from the culprit and not a victim or bystander? (They must consider context, timing, and other supporting evidence.)
- What challenges exist when collecting hairs from a crime scene? (Hairs may have been shed long before the crime or transferred from another location.)