Texas is preparing to kill a man on Thursday. This would be the country’s first execution linked to a case of “shaken baby syndrome,” a diagnosis that has been reevaluated in recent years and led to the overturning of similar convictions.

Robert Roberson, who is expected to die by lethal injection at the Texas State Penitentiary in Huntsville at 6 p.m. local time, has maintained his innocence since the death of his two-year-old daughter in 2002.

The execution could still be delayed if either Gov. Greg Abbott grants his legal team’s request for a 30-day stay or the U.S. Supreme Court intervenes.

On Wednesday, the Texas Board of Pardons and Paroles unanimously rejected a clemency recommendation for Abbott, who has the authority to commute death sentences. The board did not immediately explain why it made the decision, and Abbott has not publicly indicated what he might do.

Roberson’s attempts to appeal his conviction or at least stop his execution were unsuccessful, and the Court of Criminal Appeals again rejected a request Wednesday.

A bipartisan coalition of state lawmakers has come together to support Roberson. A committee held a hearing Wednesday that included testimony from medical experts and a retired lead investigator in the case who has since advocated for his release.

“This is, without a doubt, an innocent man,” Brian Wharton, the former detective, told state lawmakers.

The committee also issued a subpoena for Roberson to testify at a hearing next week, an unprecedented step intended to prevent Thursday’s execution. But it wasn’t immediately clear what impact the maneuver would have, and a spokesman for the Texas Department of Criminal Justice said in an email Thursday that it was working with the attorney general’s office on “next steps,” without elaborating.

In an interview from prison with NBC News anchor Lester Holt this month, Roberson, 57, called on Abbott to pardon him because “I’m innocent.”

“Look at the support I have, Mr. Governor, and I just hope and pray that you do the right thing,” he said.

Roberson has steadfastly maintained his innocence in Nikki’s death after doctors and law enforcement quickly ruled she was killed as a result of a violent concussion episode.

Prosecutors argued that Nikki must have been shaken to death because she was diagnosed with the “triad” – a swollen and bleeding brain and a retinal hemorrhage – symptoms that were once considered indisputable evidence of shaken baby syndrome.

However, since Roberson’s conviction in 2003, the scientific basis for the triad being the only diagnosis of abuse has come under intense scrutiny.

In 2009, the American Academy of Pediatrics changed the name “Shaked Baby Syndrome” to the broader definition of “Abusive Head Trauma” to include injuries caused by mechanisms other than shaking alone.

There is now a consensus in medicine that other illnesses, including infections, accidental trauma and pre-existing conditions, can also cause the symptoms associated with shaken baby syndrome.

Hundreds of cases of possibly shaken babies and abusive head injuries are reported to U.S. hospitals each year, according to a nonprofit advocacy group. While there have been criminal trials for such injuries that have resulted in convictions, scrutiny of medical testimony has also led to reversals: Since 1992, at least 34 defendants have subsequently been acquitted on allegations of shaken baby syndrome or abusive head trauma, according to the National Exoneration Registry, which provides sentences for unlawful violations Convictions recorded.

Roberson said that early on January 31, 2002, he awoke in his East Texas home to a “strange scream” and found his daughter Nikki had fallen out of bed. He comforted her and the family went back to sleep, according to court documents.

But hours later, Roberson said, he woke up to find Nikki wasn’t breathing and her lips looked blue. He took her to an emergency room, where doctors concluded she was showing signs of brain death. She was pronounced dead the next day.

Roberson showed little emotion in the hospital, increasing law enforcement’s suspicions. Within a day, Wharton, the Palestinian police officer, arrested Roberson for murder.

Wharton testified against Roberson at his trial. Prosecutors stressed that they believed Roberson intentionally shook Nikki, causing bruising and blunt force trauma, and that he appeared almost emotionless as he took her to the hospital.

Roberson has attributed his “seemingly blank reaction” to the autism spectrum disorder, which he was diagnosed with in 2018. Additionally, at his trial, his defense attorneys were not permitted to have a medical expert testify about his claims of “mental lapses” caused by a brain injury.

The jury also never heard how Nikki had been unwell since the day she was born or how she had been hospitalized more than 40 times in her short life. Two days before her death, she reported a fever of 104.5 degrees at the doctor’s office. She was sent home with a drug that has since been deemed too dangerous for children — a drug that now carries a “black box warning” from the Food and Drug Administration.

Texas nearly executed Roberson in 2016, but stopped the execution days before so another evidentiary hearing could take place. Ultimately, his request for a new trial was denied last year.

Anderson County prosecutors continue to insist in court filings that Nikki was murdered and Roberson is to blame, arguing that his defense “has raised the same tired questions that this court and others have already challenged in recent habeas proceedings.” , including junk science, disease process, etc.” actual innocence. All were rejected.”

Roberson’s attorney, Gretchen Sween, said the case has received significant support, including from dozens of renowned scientists and doctors, a bipartisan group of Texas lawmakers, parental rights advocates and organizations that support people with autism.

On Wednesday, his office was delivered a petition with more than 116,000 signatures calling on Abbott to stop the execution.