DNA Doppelganger

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 man known to police. But he did not commit the assault. Years earlier he had received a bone marrow transplant from the real perpetrator, and in doing so, inherited some of his DNA. Cases such as this are rare, but as forensic DNA databases grow and more people undergo bone marrow transplants, the risk of a miscarriage of justice increases