IT SOUNDS like an open-and-shut case: a clear DNA match is made between semen from a serious sexual assault and a blood sample from a known criminal. Yet in a recent case from Alaska, the criminal in question was in jail when the assault took place. And forensic scientists had already matched the crime sample to the DNA profile of another person who was their prime suspect. It was only after careful detective work that the mystery was solved: the jailed man had received bone marrow from the suspect many years earlier.
This week, at a meeting of the American…
