In his former life as a prosecutor, one of the high points of James G. Clark’s career was winning the conviction of Edward R. Grant.

That moment came in 2002, nearly 30 years after Concetta “Penney” Serra, a 21-year-old dental assistant, had been found stabbed to death in the Temple Street Parking Garage in New Haven. As far as cold cases go, this one was frozen. It was solved with the help of DNA evidence that was traced to Grant in 1999.