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?