On the night of June 20, 1987, John Sweek and his wife Sally were found dead inside their Dallas, Texas apartment. John was twenty-seven years old; Sally was twenty-one. The crime that ended their lives would also begin the wrongful destruction of another man's — a slow-motion miscarriage of justice that would take more than twenty-five years to reverse.
Dallas investigators processing the crime scene recovered numerous pieces of physical evidence. Among the findings was what appeared to be a human bite mark on one of the victims. This detail would prove decisive in the prosecution that followed — not because it pointed to the true killer, but because it pointed to a forensic technique that courts had long treated as reliable and that, in the decades to come, would be thoroughly discredited.
Several days after the murders, an anonymous caller contacted police with information implicating a man named Steven Mark Chaney. The caller claimed that he and Chaney had been regular visitors to the Sweek apartment, buying cocaine there multiple times a week. A second source told investigators that Chaney owed John Sweek money — a potential motive. Investigators had a name, a motive, and a forensic clue. They had what looked like a case.