The murders of two young women near a Phoenix canal in the early 1990s remain unsolved for over 20 years until a team of cold case detectives take on the case. Friday's all-new Dateline examines how investigators used inventive techniques and groundbreaking advancements in forensic genealogy to unmask the killer.INTERVIEWS WITH: Former Phoenix Police Department Sergeant Troy Hillman, Defense attorney RJ Parker, forensic genealogist Dr. Colleen Fitzpatrick, co-workers of the victims, and others.