Prosecutors said the plainclothes officer was chasing Rivera near City Hall in August 2006 when Rivera shot him in the chest.
Rivera testified he saw someone with what looked like a gun running after him but did not know Wertz was a policeman.
The jury will reconvene next week to decide whether Rivera will get the death penalty or life in prison.
Rivera's lawyer, Jay M. Nigrini, said in his closing argument Friday that Rivera feared for his life. "Rivera did not know Wertz was a police officer," Nigrini said repeatedly.
Senior Deputy Attorney General K. Kenneth Brown II said it made no difference whether Rivera knew Wertz was a police officer. He reminded jurors that Rivera admitted on the witness stand firing two shots with the intent to kill Wertz, 40, of Spring Township.
"The defendant admitted this was a malicious killing," Brown said. "He had it in his mind he was going to kill someone pursuing him and he did."
Wertz was working an auto-theft detail at the time of the shooting. He had been responding to a report of a fight, and gave chase when he saw Rivera stuff something down the front of his pants and run, police have said.
A jury was brought in from Northampton County because of extensive media coverage of the case in the Reading area.
Wednesday was the second anniversary of Wertz' killing.
