ABSTRACT
Any tissue containing partially intact DNA provides useful samples: semen (in rape cases), blood, hair, skin fragments, mouth epithelial cells (in saliva), or bones in skeletons. Forensic (law-related) science can compare the genetic characteristics of biological fragments found at the scene of a crime (presumed to come from the criminal) to a suspect to exclude or associate them. Any biological sample from a person will match that person in all genetically determined characteristics. The great power of the technique is to exclude the innocent. A single genetic character that does not match can prove that the suspect did not deposit the sample. If enough suitable genetic characteristics do match, that is evidence ‘beyond reasonable doubt’ that the suspect did deposit the sample. The court can then test the suspect’s explanation of this ‘contact’ with the crime scene.
