Trace evidence Sometimes physical evidence is very small or even invisible to the untrained eye. This type of evidence is called trace evidence. It includes things like fingerprints or footprints in and around the area where a crime took place. It could also include very small physical objects like a hair or fibre from a piece of clothing. This type of evidence must be collected or photographed by experts. If you are the first one to arrive at a scene of a crime, it is important for you to make sure the crime scene is not changed in any way before the experts arrive.