Abu-Jamal has been on death row for 25 years
A US federal appeals court has overturned the death sentence imposed on former Black Panthers member Mumia Abu-Jamal.
The court said Abu-Jamal's conviction for murdering a Philadelphia police officer should stand, but that he should have a new sentencing hearing.
The former radio journalist and activist was sentenced to death for the murder in 1982.
While in jail he became a leading campaigner against the death penalty.
He appealed against the sentence, on the grounds that racism on the part of the judge and the prosecutors had corrupted his conviction, which was by a jury of 10 white and two black people.
The Third US Circuit Court of Appeals found on Thursday that the jury had been given flawed instructions over how to consider mitigating circumstances to the crime.
"The jury instructions and the verdict form created a reasonable likelihood that the jury believed it was precluded from finding a mitigating circumstance that had not been unanimously agreed upon," the court wrote.
Abu-Jamal's lawyer says the case has been marked by racial prejudice
The Free Mumia Abu-Jamal Coalition, which has campaigned for a fresh trial, described the ruling as a "devastating decision", and called for mass protests on Friday.
A federal judge in 2001 also came to the conclusion that Abu-Jamal should be given a new sentencing hearing because of the jury instructions - but this decision was appealed against by prosecutors.
Thursday's decision upheld the 2001 judgement.
The police officer killed, Daniel Faulkner, pulled over Abu-Jamal's brother one night in December 1981 for driving the wrong way down a one-way street.
Abu-Jamal denied killing the officer, and says he himself was shot while running away.
The officer's widow, Maureen Faulkner, recently co-wrote a book about the case, called "Murdered by Mumia: A life sentence of loss, pain and injustice".