Bootleggers Daughter by Margaret Maron

Deborah Knott is appalled by the utter disregard for mercy as she watches her least favorite judge declare the toughest possible sentence on a black man.  She decides to run for a judgeship herself.  A young woman whose mother was murdered when she was just an infant wants to pay Deborah to find out why her mother was killed.  Between her campaign and asking around about the incident that had happened 18 years ago, other people begin to die.  In the end, Deborah figures out who and saves the girl again.  But she loses the election.  However her least favorite judge is felled by a stroke, and her father calls in some favors to get her appointed to take his place.