The Supreme Court has barred Louisiana from executing a convicted killer, saying his mental disability precludes capital punishment.
The ruling comes in a 5-4 decision Thursday.
Kevan Brumfield was convicted in the shooting death of off-duty Baton Rouge police Cpl. Betty Smothers in 1993.
A federal judge ruled that Brumfield was mentally disabled and therefore was protected from execution under a Supreme Court decision in 2002.
But the federal appeals court in New Orleans reversed the judge's ruling.
Brumfield and Henri Broadway of Baton Rouge were convicted and sentenced to death for ambushing Smothers on Jan. 7, 1993 as she was driving a grocery store manager to make a bank deposit.
The 36-year-old Smothers was working as an off-duty security officer at the time.