The Drop by Michael Connelly

The open unsolved unit of the Los Angeles Police Department looks into unsolved murders going back 50 years. Of the 10,000 cases still open, using DNA can put new life into a cold case. Harry Bosch and David Chu handle such cases. Bosch finds that confronting killers years later who think they have gotten away with murder very addictive.
Bosch and Chu are given a cold case from 1989 involving rape and murder as well as a current case where the son of his arch enemy Irvin Irving was pushed or fell to his death.
Michael Connelly has a website: www.michaelconnelly.com