Red herring : a Joe Gunther novel / Archer Mayor.

Enhanced descriptions from Syndetics:

VBI (Vermont Bureau of Investigation) head Joe Gunther and his team are called in to investigate a series of violent deaths that appear unrelated until telltale clues reveal a linkage between them and that all of the deaths are, in fact, murders. However, apart from a single drop of unexplained blood left at each crime scene, there are no obvious connections between the victims or the cases. The police are faced with more questions than answers including what do the mysterious deposits of blood mean, coming as they do from three additional unknown people. In their search for the elusive truth, the VBI must plumb the depths of every suspect's past, every victim's most intimate details, and examine each piece of evidence down to the smallest detail--an examination which includes a trip to the Brookhaven National Lab on Long Island and an exploration of cutting edge forensic technology.