Philadelphia District Attorney Seth Williams says he will appeal a federal court decision granting a new sentencing hearing for convicted killer Mumia Abu-Jamal.

Abu-Jamal was convicted in 1982 of the shooting death of Philadelphia Police Officer Daniel Faulkner.

The Tuesday ruling from the U.S. appeals court is the latest in the decades-long courtroom saga involving the 58-year-old Abu-Jamal, a former journalist and Black Panther.

The case has garnered international attention, protests and books. On the one side are Abu-Jamal's supporters, who believe he is innocent. On the other side, are Faulkner's family and friends, who believe Abu-Jamal should be executed. After decades of appeals, Abu-Jamal remains on death-row.

While the Tuesday decision means Abu-Jamal might get a life sentence instead of the death penalty, it does not change his first-degree murder conviction.

The appeals court granted Abu-Jamal a new hearing after determining the original trial judge issued confusing instructions to the jury when it came to the sentencing phase.

Williams had appealed that decision to the U.S. Supreme Court. The high court handed the case back to the Third Circuit Court of Appeals in Philadelphia, which once again ruled Abu-Jamal deserves a new sentencing hearing.

Abu-Jamal's attorney, Judith Ritter, said four federal judges have now ruled that the sentencing phase of the trial was unconstitutional.

"In 2001, the death penalty was set aside. And we haven't been able to feel comfortable that that decision has stuck. And hearing the Third Circuit today, re-affirm its decision, it's very, very significant," she said, adding that she believes the ruling will stand.

Williams, who maintains the jury instructions were correct based on the law at that time, said when it comes to Abu-Jamal's case, it's not an issue of guilt or innocence.

"This is not a case of whodunit. The court of appeals ruled that this is not a new evidentiary hearing. That Mumia Abu-Jamal did in fact kill Officer Daniel Faulkner in 1981. The question is will we let him remain in jail or ask for the death penalty," Williams said.

Suzanne Ross, spokeswoman for the International Concerned Family and Friends of Mumia Abu-Jamal, said the group wants "Mumia free and life in prison without parole is never what we wanted. But the looming threat of execution is not something we took lightly."

Williams said he spoke to Faulkner's widow, Maureen Faulkner, after the ruling. He said she is upset and wants his office to continue pursuing the death penalty.

Williams says it could take years to settle the issue.

"Of course it's a hot-button issue for Americans whether or not we should have the death penalty. But the fact is that the Supreme Court, the courts of appeals, ruled that clearly Mumia Abu Jamal killed Officer Faulkner," he said. "So I don't want to get into the whole comic book nature of people who think otherwise."