Forensic Files S05E07 - Trail of Truth

A mother and her two young daughters are found brutally murdered and sexually violated. The crime scene has no shortage of evidence, but investigators cannot find a conclusive link to their prime suspect. To solve the puzzle, an FBI analyst designs a unique experiment, in which pubic hairs found at the scene are used to establish not only that the perpetrator was in the home, but that he was there when the crime was committed.