Forensic Iodine Fuming

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Updated on Apr 18, 2013

Iodine fuming is one of the oldest forensic techniques used to develop latent fingerprints but it is also one of the easiest. Students will learn how to fume iodine crystals that are readily available from any science supply store or school lab to develop invisible fingerprints on a piece of white paper.


The objective of this experiment is to use iodine vapors to develop latent fingerprints on a non-porous object.


  • Iodine crystals
  • Small, clear plastic container with lid
  • Small piece of white paper


  1. Cut a small piece of paper approximately 4”x4”.
  2. Run your fingers through your hair or across your forehead.
  3. Use that same hand to deposit fingerprints on the paper.
  4. Don’t worry if you can’t see the fingerprints!
  5. Place the paper inside the plastic container.
  6. Sprinkle 4-5 crystals of iodine in the bottom of the container and then close the lid.
  7. Hold the small container in your hand to add some heat to the experiment.
  8. You will begin to see the violet-colored fumes starting to appear.
  9. After several minutes the iodine fumes will adhere to the amino acids in your fingerprint secretions,leaving clear, brown fingerprints that were not previously visible.
Detective Constable Jake Friesen is a member of the Forensic Identification Unit with the Peterborough Lakefield Community Police Service in Ontario, Canada. Jake is highly trained in many disciplines of forensic science and is a fingerprint expert in Canada.

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