A date has not yet been set for the competency hearing.
Montgomery, 52, was scheduled to die by lethal injection on Tuesday, January 12, at the Federal Correctional Complex in Terre Haute, Indiana.
Prosecutors filed a notice to appeal the judge’s decision.
Montgomery’s lawyers, family members and supporters begged President Donald Trump to read his clemency petition and make the executive decision to commute his sentence to life without the possibility of parole.
Montgomery was sentenced to death in 2008 by a Missouri jury for the murder of a pregnant woman in 2004, cutting the fetus and kidnapping it. The baby survived.
“The court was right to prevent the execution of Lisa Montgomery,” said his lawyer, Kelley Henry, in a statement. “As the court concluded, Ms. Montgomery ‘gave a strong demonstration’ of her current incompetence to be executed. Mrs. Montgomery has brain damage and severe mental illness that was exacerbated by the sexual torture she suffered at the hands of caregivers. “
“The Eighth Amendment prohibits the execution of people like Mrs. Montgomery who, due to their severe mental illness or brain damage, do not understand the basis of their executions. Mrs. Montgomery is deteriorating mentally and we are looking for an opportunity to prove her incompetence, “Henry added.
Montgomery also has a petition before the US Supreme Court.