Kathy Taft was bludgeoned and raped on March 5, 2010, as she lay in the bedroom of a friends’ home in Raleigh recovering from surgery. She died four days later. Raleigh police tracked down her killer, Jason Williford, through what then-police chief Harry Dolan called “gumshoe detective work”: They collected and tested trash discarded by neighborhood men who refused to provide samples of their DNA.