The only woman on America's federal death row has had her execution halted - just hours before she was due to receive a lethal injection.
In 2004, Lisa Montgomery strangled a pregnant woman to death before cutting the baby from the womb and fleeing with it.
Prosecutors said that after Montgomery kidnapped the child, she attempted to pass the infant off as her own.
Montgomery, now aged 52, was due to be executed on Tuesday at the Federal Correctional Complex in Terre Haute, Indiana. However, Judge James Hanlon said a competency hearing should be held first.
Montgomery's lawyers have argued that sexual abuse during her childhood led to mental illness.
Had the execution have gone ahead, she would have been the first female federal inmate to be put to death in almost six decades.
On Monday, Judge Hanlon of the US District Court for the Southern District of Indiana wrote: "Ms Montgomery's motion to stay execution is granted to allow the court to conduct a hearing to determine Ms Montgomery's competence to be executed.
"Ms Montgomery's current mental state is so divorced from reality that she cannot rationally understand the government's rationale for her execution."
He added that a time and date for the hearing will be released "in due course".
This is the second time that Montgomery's execution has been halted.
She was originally scheduled to be put to death on December 8, but the execution was temporarily blocked after her attorneys contracted the coronavirus after visiting her in prison.
Montgomery was one of three inmates scheduled to be executed by the Justice Department this week, just days before President-elect Joe Biden takes the oath of office.
Biden opposes the death penalty, and his spokesman has said he’ll work to end its use.
The Justice Department resumed executions in July after a nearly 20-year hiatus.
Anti-death penalty groups said President Donald Trump was pushing for executions prior to the November election in a bid to burnish a reputation as a law-and-order leader.
On the other hand, US officials have portrayed the executions as bringing long-delayed justice for victims and their families.