A break and enter has just occurred in your neighbourhood and the homeowners are very upset. The police are on scene but can’t seem to find any clues. They have called you in to examine the scene for footprints and fibers.
When you arrive, the homeowners tell you that the suspect was in their kitchen. At first glance, there does not appear to be any evidence on the floor. However you know better! Here is a simple technique called oblique lighting that is used every day by forensic specialists: