Physical evidence deals with material objects. It may be material left or taken from the scene of a crime by the suspect or victim, or it might be an impression left in some material. It includes not only fingerprints and footprints, but also hair, fibers, blood, arson accelerants, glass, or almost anything that can be deposited and collected.
Physical evidence is often necessary to prove that a crime had been committed.
For instance, the presence of accelerants at a fire scene indicates an arson, and the presence of heroin constitutes a crime if connected to a suspect. The amount of consideration given to physical evidence depends on whether the evidence has individual or class characteristics. Evidence with individual characteristics can definitely be identified with a person or source if sufficient microscopic or accidental markings are present. Some examples include fingerprints, handwriting, firearms, bullets, tool marks, shoe prints, and pieces of glass in cases in which broken edges can be matched. Evidence with class characteristics, no matter how thoroughly examined, will only be placed in a class or group.