(Adds Montgomery's lawyers appealing to U.S. Supreme Court, other details)
By Jonathan Allen and Bhargav Acharya
Jan 12 (Reuters) - Legal challenges were being fought in multiple federal courts on whether to allow Tuesday's scheduled execution of convicted murderer Lisa Montgomery, the only woman on federal death row in the United States, who doctors say is brain-damaged and mentally ill.
It is one of three executions the U.S. Department of Justice had scheduled for the final full week of President Donald Trump's administration, and would mark the first time the U.S. government has executed a woman since 1953.
Whether it proceeds will likely fall to the U.S. Supreme Court, whose conservative majority has previously allowed all of the 10 previous executions last year under death penalty proponent Trump, a Republican, to proceed.
President-elect Joe Biden, a Democrat, takes office on Jan. 20, and says he will seek to abolish the federal death penalty.
On Monday, the U.S. Court of Appeals for the District of Columbia Circuit voted to stay the execution to hold hearings on whether the Justice Department gave insufficient notice of Montgomery's execution date. The Justice Department has asked the Supreme Court to overturn that stay.
Also on Monday night, a federal judge in Indiana ordered the execution to be postponed to allow for a hearing on whether she was too mentally ill to be executed. But the 7th U.S. Circuit Court of Appeals in Chicago overturned the stay on Tuesday afternoon, a ruling that Montgomery's lawyers have since asked the Supreme Court to overturn.
Around the same time, the St. Louis-based 8th U.S. Circuit Court of Appeals issued its own stay of the execution, siding with her lawyers that the government had scheduled her execution in violation of the original sentencing court's judgment issued in 2007.
Montgomery, 52, had been scheduled to be killed by lethal injections of pentobarbital, a powerful barbiturate, at 6 p.m. EST (2300 GMT) on Tuesday in the Justice Department's execution chamber at its prison in Terre Haute, Indiana.
She was convicted in 2007 in Missouri for kidnapping and strangling Bobbie Jo Stinnett, then eight months pregnant. Montgomery cut Stinnett's fetus from the womb. The child survived. Some of Stinnett's relatives have traveled to witness Montgomery's execution, the Justice Department said.
In the Indiana ruling, U.S. District Judge James Patrick Hanlon granted a stay to allow the court to conduct a competency hearing. The Supreme Court holds that executing an insane prisoner breaches a constitutional ban on "cruel and unusual" punishments.
Doctors who have examined Montogomery and scans of her brain say that her brain shows sign of structural damage and that she has bipolar disorder, among other mental illnesses. Her lawyers say the brain damage likely stemmed from her mother's alcohol abuse during her pregnancy with Montgomery and from her stepfather often slamming Montgomery's head against a concrete floor while raping her as a child.
She has auditory hallucinations, has expressed uncertainty about whether the child of the woman she killed was really her own, and has said that God speaks with her through connect-the-dot puzzles, according to court filings.
Justice Department lawyers countered with transcripts of Montgomery's prison phone calls they said showed she understood her execution date was drawing near.
Montgomery's lawyers asked for Trump's clemency last week, saying she committed her crime after a childhood in which she was abused and repeatedly raped by her stepfather and his friends and pimped out for sex by her mother, and so should instead face life in prison.
Federal executions had been on pause for 17 years and only three men had been executed by the federal government since 1963 until the practice was resumed last year under Trump, whose outspoken support for capital punishment long predates his entry into politics.
His administration had also set execution dates for two men convicted of murder on Thursday and Friday, but a U.S. judge in Washington ordered their executions be delayed until at least March 16 in order to allow them to recover from COVID-19. The Justice Department has appealed that order. (Reporting by Jonathan Allen in New York and Bhargav Acharya in Bengaluru; Additional reporting by Kanishka Singh and Lawrence Hurley; editing by Robert Birsel, Jonathan Oatis and Grant McCool)