Showing Guilt by Degrees by Marcia Clark

Rachel Knight has never been one to let justice slide from the grip of the law. So when a deputy district attorney mishandles a murder case and then shrugs it off - the victim was a homeless guy, so who cares? - she decides to take the case on herself.
With the help of Detective Bailey Keller, Rachel soon finds a missing piece of the puzzle. And a new mystery: the homeless man's death is somehow connected to the vicious murder of a LAPD cop a year earlier.
The prime suspect in the murder was acquitted - but now Rachel and Bailey are hot on the trail of new leads. What Rachel doesn't know is that she's being watched. Someone is following her every move, and just waiting for a chance to strike...