took, what i had to do. now, dna from genealogy websites is revolutionising cold case murder investigations like grace's, but at what cost? we have a multibillion—dollar industry unearthing the secrets of our genes. you have an absolute right to privacy but, at the same token, we have a right to not get murdered and raped. so who was grace and can america's dna detectives find out who killed her? i'm here in the middle of the us to follow a case that has stumped the police for more than 30 years now. and i'm particularly interested in it because the police are using a technique involving dna tracing that's