Locard's Principle is concerned with(2018)

Locard's Exchange Principle: When any two objects come into contact, there is always a transfer of material from each object on the other. Trace from the scene may be carried away on the person or tool of the criminal, and at the same time, traces from all or any of these may be left at the scene. Wherever a criminal goes, whatever he touches, and whatever he leaves will serve as silent evidence against him. e.g., fingerprints, footprints, hair, fibres from clothes. broken glass, tool marks, paints, scratches, blood or seminal stains, etc. It is actual evidence, and its presence is absolute proof of the crime. Ref:- k.s.narayan reddy; pg num:- 475