Flesh and Blood by Patricia Cornwell

In this Kay Scarpetta novel, the master forensic sleuth finds herself in the unsettling pursuit of a serial sniper who leaves no incriminating evidence except fragments of copper. 

It’s Dr. Kay Scarpetta’s birthday, and she’s about to head to Miami for a vacation with Benton Wesley, her FBI profiler husband, when she notices seven pennies on a wall behind their Cambridge house. Is this a kids’ game? If so, why are all of the coins dated 1981 and so shiny they could be newly minted? Her cellphone rings, and Detective Pete Marino tells her there’s been a homicide five minutes away. A high school music teacher has been shot with uncanny precision as he unloaded groceries from his car. No one has heard or seen a thing.

The shots seem impossible, yet they are so perfect they cause instant death. The victims appear to have had nothing in common, and there is no pattern to indicate where the killer will strike next. First New Jersey, then Massachusetts, and then the murky depths off the coast of South Florida, where Scarpetta investigates a shipwreck, looking for answers that only she can discover and analyze. And it is there that she comes face to face with shocking evidence that implicates her techno genius niece, Lucy, Scarpetta’s own flesh and blood.