At Risk by Patricia Cornwell

A Massachusetts state investigator is called home from Knoxville, Tennessee, where he is completing a course at the National Forensic Academy. His boss, the district attorney, attractive but hard-charging, is planning to run for governor, and as a showcase she's planning to use a new crime initiative called At Risk-its motto: "Any crime, any time." In particular, she's been looking for a way to employ cutting-edge DNA technology, and she thinks she's found the perfect subject in an unsolved twenty-year-old murder-in Tennessee. If her office solves the case, it ought to make them all look pretty good, right?

Her investigator is not so sure-not sure about anything to do with this woman, really-but before he can open his mouth, a shocking piece of violence intervenes, an act that shakes up not only both their lives but the lives of everyone around them. It's not a random event. Is it personal? Is it professional? Whatever it is, the implications are very, very bad indeed . . . and they're about to get much worse.