ForensiKit

Want another evidence packaging activity?

Where have you been?

In forensics, Locard’s Exchange can be summed up as the principle that any time you have contact with another person, place or thing, you leave something behind and you take something away with you.

For criminal investigations, that means the perpetrator leaves evidence behind at a crime scene (e.g., a fingerprint, a hair, etc.) and also takes something from the crime scene away with them (e.g., a carpet fiber, a pet hair, etc.).

That evidence can be used to connect a suspect to a crime scene.

For more information, see The Cornerstone of Forensic Science: Locard’s Exchange Principle by Douglas P. Lyle

Ready to try it for yourself?

You can do this activity on your own, or divide into teams and examine the other team’s evidence.

1. Get a freshly laundered t-shirt.
2. Examine the t-shirt for any trace evidence like hairs or fibers. If you find any, remove them.
3. Wear the t-shirt for four hours or longer and do the same things you usually do. Keep track of where you go and what you do during the time you’re wearing that t-shirt.
4. Remove the shirt (and exchange with the other team, if there is one).
5. Examine the shirt under a bright light.
6. List all the evidence you can find like hairs, fibers, stains, etc.
7. Collect as much of the evidence as you can following the procedure.
8. Write down your theory of where each evidence item came from (the neighbor’s cat, the classroom/office carpet, etc.)
9. Compare your list of theories with the t-shirt wearer’s log of activities. Were your theories accurate?

---

---