All That Remains, by Patricia Cornwell

Young lovers are ending up dead, found partially skeletonized in remote woodland areas with no apparent cause of death. Chief Medical Examiner Kay Scarpetta is baffled, and she fears the "Couple Killer" will strike again. The most recent victim was the daughter of a powerful political drug activist, and the search for the killer intensifies. Kay soon learns that the government is withholding evidence, and the only thing more shocking is why they've done so: they fear the sociopath stalking young couples is one of their own...