According to Dr Edmond Locard's exchange principle, every contact leaves a trace. In physicochemical forensic investigations¹  the traces are small fragments of any materials such as car paints, fibers, glass fragments, polymers, etc. left behind or taken away from the crime scene by the perpetrator or a victim during the crime (theft, burglary, murder, car accident, etc.). The small size of such microtraces make them easily transferrable between objects (e.g. weapons) and individuals. Thanks to this, they help investigators to establish a connection between the crime scene, the perpetrator and the victim, and to reconstruct the event.

If the traces collected during the crime scene investigation are large enough, toolmarks analysis such as jigsaw fitting is feasible for finding whether the traces may have been parts of a particular object. Otherwise, the analysis of microtraces is carried out for three different purposes:¹