SPRINGFIELD, Ill. (AP) _ The state Supreme Court ordered a new trial for a death row inmate convicted of killing a police officer, saying the jury wasn't instructed properly.

The McLean County jury was unaware that it could have convicted Manuel Salazar of voluntary manslaughter, which usually carries a sentence of four to 15 years, the court said Thursday.

Salazar, who has been on death row since December 1985, said he shot the officer Martin Murrin in self-defense during a struggle. Salazar, 28, fled to Mexico after the September 1984 slaying and was extradited.

The Mexican government later appealed to U.S. authorities to overturn the death sentence, saying it would never have allowed the extradition if it had known he could face a death penalty.

Hispanic groups supported Salazar, insisting he acted in self defense.

Properly instructed jurors might have found that Salazar believed the Joliet police officer was going to shoot him, Justice Mary Ann G. McMorrow said.

''I'm ecstatic,'' said Charles Hoffman, Salazar's lawyer. ''We've always contended Manuel should get a new trial and now the court has agreed with us, six to one.''

Prosecutors will ask state Attorney General Roland Burris to seek a rehearing before the state Supreme Court and will go to the U.S. Supreme Court if rejected.

State Sen. Ed Petka, who prosecuted the case in 1985, said the jury instructions given at trial were standard at the time.

''Ten years after the crime, nine years after the trial and six years after the Supreme Court affirmed, we get a decision that says things were done wrong,'' he said.

Prosecutors argued that the evidence presented at trial showed Salazar was not justified in killing Murrin, who was shot five times, because Salazar was attempting to escape arrest when he attacked the officer.

Justice Benjamin Miller, the only justice to object to a new trial, said he didn't agree that Salazar's previous defense counsel was ineffective for failing to raise the instruction issue in an unsuccessful 1988 appeal.