Lisa Montgomery, who killed a pregnant woman by strangling and cutting the unborn baby from her womb, was executed by lethal injection at a federal prison in Indiana before dawn Wednesday.

The Associated Press reported that she was pronounced dead at 1:31 a.m. The 52-year-old Kansas killer was the first woman executed by the federal government since 1953 and the only female on death row. 

Her execution happened after the Supreme Court gave the Justice Department the green light to carry out the act. 

On Tuesday, the high court ditched the defense attorneys' argument that Lisa Montgomery must be given a competency hearing to prove her mental illness. It will have made her ineligible for the death penalty if she's proven suffering from a severe mental disorder.

The Supreme Court relayed its decision after midnight on Wednesday, which grants the federal Bureau of Prisons to proceed with the execution of Lisa Montgomery, according to a KRMG report.

Lisa Montgomery was the 11th federal death row inmate to be executed since July when President Donald Trump resumed federal executions after a 17-year pause.

Her execution comes as another court holds two other executions set later this week because the prisoners tested positive for coronavirus.

Montgomery's execution was among the last before President-elect Joe Biden sworn-in next week. Biden is a staunch critic of the death penalty.

Reports said that a woman standing near Montgomery's gently removed her face mask and asked her for any last words as the execution process started. She replied, "No," in a quiet and subdued voice and said nothing else.

Related story: Execution of Only Woman on Federal Death Row Postponed

Lisa Montgomery's Lawyers Claims

Montgomery's lawyers have long claimed that she was mentally ill and cannot comprehend that she would be put to death. Many courts had issued injunctions. However, there were all later lifted by appeals courts or the Supreme Court.

One of Montgomery's lawyers, Kelly Henry, said her client was transferred from a Texas prison to the Terre Haute facility in Indiana late Monday night.

Henry said this was due to the lack of facility for female inmates, and Montgomery stayed at the execution-chamber building.

"I don't believe she has any rational comprehension of what's going on at all," Henry told The Associated Press. According to Henry, Lisa Montgomery made gloves, hats, and other knitted items to give as gifts for her lawyers and others.

She added that Montgomery has not been able to continue that activity or read as her glasses were taken away from her over claims that she could harm herself.

Montgomery's legal team said she suffered sexual torture, including gang rapes, when she was a child. Her lawyers also claimed that these incidents permanently scarred her emotionally and worsened her mental health issues that ran in her family.

The prosecutors had accused Montgomery of faking her mental illness at a trial, ABC News reported.

Lisa Montgomery's Crime

Lisa Montgomery allegedly killed Bobbie Jo Stinnett on Dec. 16, 2014 in her Missouri home. Stinnett was eight months pregnant when Montgomery strangled her to death with a rope and cut her baby from her womb with a kitchen knife.

The baby girl survived, and Montgomery went on to claim it as her own, according to a KMBC report. Stinnett was a dog breeder, and her husband was working when she was killed.

Montgomery met Stinnett online and said that she was interested in buying a rat terrier. Montgomery also pretended to be pregnant to bond with her victim.

The suspect had researched home births and how to perform cesarean sections online before the attack. Police found Montgomery in her Kansas farmhouse sitting in the living room with a newborn in her arms. Police rescued the baby, and they returned her to her dad.

Bonnie Brown Heady was the last woman executed by the federal government on Dec. 18, 1953 for kidnapping and killing a six-year-old boy in Missouri. 

Related story: Judge Postpones Execution of Only Woman on Federal Death Row