Closing arguments are set to begin in the murder trial of Guy Rivera, accused of fatally shooting NYPD detective Jonathan Diller. Police allege that Rivera was in the passenger seat of a car when he pulled a gun and shot Diller through the window, causing him to be shot in the back. His defense claims that the gun went off accidentally during a chaotic scene and that he did not intend to harm an officer. If convicted, Rivera faces up to life without parole.