Righteous Kill

Righteous Kill is a movie starring Robert De Niro, Al Pacino, and Carla Gugino. Two veteran New York City detectives work on a case of serial executions of criminals who escaped justice.
Two veteran New York City detectives work to identify the possible connection between a recent murder and a case they believe they solved years ago; is there a serial killer on the loose, and did they perhaps put the wrong person behind bars?