AND THE DEVIL WALKS AWAY by Kevin R. Doyle

Helen Lipscomb seemingly has nowhere to go but down. Cashiered from the force, ostracized by most of her former acquaintances, and with no real connections left to the community, she's been getting by as a sort of unofficial investigator, doing piecework for various lawyers and bail bondsmen. Her former life as a homicide detective seems far behind her until a notorious serial killer, locked away and facing the death penalty, offers her the challenge of a lifetime. Not to prove his innocence, but to prove him guilty of even more murders than the authorities suspect, murders for which another convicted man, several states away, is taking credit.