Not only his fingerprints or his footprints, but his hair, the fibres from his clothes, the glass he breaks, the tool mark he leaves, the paint he scratches, the blood or semen he deposits or collects.
Only human failure to find it, study and understand it, can diminish its value.Fragmentary or trace evidence is any type of material left at (or taken from) a crime scene, or the result of contact between two surfaces, such as shoes and the floor covering or soil, or fibres from where someone sat on an upholstered chair.
Locard's Principle also holds in computer forensics, where committing cyber crime will result in a digital trace being left behind.
[3] In Season 3 Episode 15 of Father Brown, Inspector Sullivan and Frank Albert discuss this principle, which plays into the investigation.
In season 2, episode 21 of Law & Order: Special Victims Unit, Locard's principle is mentioned and used in the investigation into a serial killer.