by KYW's Tony Hanson

A Philadelphia jury is now hearing the retrial case of a man accused of murdering a city police officer in 1985.

Defendant Wilfredo Santiago had been convicted previously, but the conviction was thrown out and the case has been tied up in the courts until now.

Prosecutor Carlos Vega told the jury in this latest trial that the evidence will show that Santiago killed officer Thomas Trench by shooting him twice at close range as the officer sat in his marked patrol car near 17th and Spring Garden Streets.

Vega contends that Santiago was out to settle a score with another police officer who had been driving the same patrol car -- number 912 -- just hours earlier, and that Santiago rode up on a bike and shot Trench in the face.

But Santiago has pleaded not guilty, and the defense contends that prosecution witnesses, including several jailhouse informants, are lying and that the verdict should be not guilty.

Santiago, now 44, has been serving an unrelated prison sentence for the past three years. Before that he had been free on bail after his first murder conviction was thrown out. An appeals court ruled that the trial judge and prosecutors had acted improperly in his first trial, and that evidence had been withheld.