Prosecutors in Philadelphia announced Wednesday that they had halted the state’s effort to execute Mumia Abu-Jamal, the death row inmate convicted of killing a police officer 30 years ago, whose subsequent legal case based on claims of innocence has received international attention.

Mr. Abu-Jamal will spend the rest of his life in prison without the possibility of parole, said Seth Williams, the district attorney for Philadelphia.

“This has been a very, very difficult decision,” Mr. Williams said at a news conference, adding that he believed Mr. Abu-Jamal was guilty of the murder and should be executed. “The sentence was appropriate. That would have been the just sentence for this defendant.”