Barring intervention by the courts or the governor, Texas on Thursday is scheduled to execute death row inmate Robert Roberson, who claims he was wrongfully convicted of abusing his 2-year-old daughter until she died.

But the status of the execution process is now unclear after an extraordinary decision by a Texas House committee Wednesday night to subpoena Roberson to testify as it reconsiders the lawfulness of his conviction.

“It’s a historic, unprecedented step. We’ll see what happens next,” said GOP state Rep. Jeff Leach, who was among the seven representatives who voted in favor of the motion to subpoena.

The Texas Department of Criminal Justice has not announced whether Roberson’s execution will be delayed due to the subpoena from the Texas Committee on Criminal Jurisprudence, which calls for Roberson to testify October 21. The department said Wednesday night that it was discussing “appropriate next steps” with the state attorney general’s office.

If he’s put to death, Roberson’s attorneys say he would be the first person in the US executed for a conviction that relied on an allegation of shaken baby syndrome, a misdiagnosis in Roberson’s case, they argue, and one they say has been discredited.

While child abuse pediatricians fiercely defend the legitimacy of the diagnosis, Roberson’s advocates say the courts have yet to consider ample evidence his daughter, Nikki Curtis, died not of a homicide, but a variety of causes, including an illness and medicine now seen as unfit for such a sickly child.

The pleas of Roberson’s many supporters have so far done nothing to halt the march toward his execution and his conviction has until now been upheld on appeal.

But his attorneys continue to try to make their case in the courts: They’ve filed a request for a stay of execution with the US Supreme Court, arguing his due process rights were violated when the Texas Court of Criminal Appeals declined to consider additional evidence the inmate says would support his innocence claim.

Texas urged the Supreme Court in a filing Wednesday evening to deny Roberson’s emergency appeal, claiming that the arguments he has raised are “unworthy of the court’s attention.”

The courts, Texas officials said, “gave Roberson the means and the opportunity to make claims, marshal evidence in support of his cause, and address the adverse evidence adduced against him.” Just because Roberson was denied, the state officials told the Supreme Court, “does not mean that he was denied notice or an opportunity to be heard.”

“The record shows that the state habeas proceedings adequately complied with due process,” Texas told the Supreme Court in its brief.

Earlier Wednesday, the Texas Board of Pardons and Paroles declined to recommend clemency after his attorneys requested his death sentence be commuted to a lesser penalty – or that the inmate be granted a 180-day reprieve to allow time for his appeals to be argued in court.

Without the recommendation of the parole board, GOP Gov. Greg Abbott is limited to issuing a one-time, 30-day delay of the execution to allow court appeals to play out. CNN has reached out to Abbott’s office for comment.

Roberson’s innocence claim underscores an inherent risk of capital punishment: A potentially innocent person could be put to death. At least 200 people – including 18 in Texas – have been exonerated since 1973 after being convicted and sentenced to die, according to the Death Penalty Information Center.

‘I am ashamed,’ former detective says

At the time of her death, Nikki had double pneumonia that had progressed to sepsis, they say, and she had been prescribed two medications now seen as inappropriate for children that would have further hindered her ability to breathe. Additionally, the night before Roberson brought her to a Palestine, Texas, emergency room, she had fallen off a bed – and was particularly vulnerable given her illness, Roberson’s attorneys say, pointing to all these factors as explanations for her condition.

Other factors, too, contributed to his conviction, they argue: Doctors treating Nikki “presumed” abuse based on her symptoms and common thinking at the time of her death without exploring her recent medical history, the inmate’s attorneys claim. And his behavior in the emergency room – viewed as uncaring by doctors, nurses and the police, who believed it a sign of his guilt – was actually a manifestation of autism spectrum disorder, which went undiagnosed until 2018.

“I told my wife last week that I’m ashamed. I’m ashamed that I was so focused on finding an offender and convicting someone that I did not see Robert. I did not hear his voice,” Brian Wharton, the former detective who oversaw the investigation into Nikki’s death, told state lawmakers Wednesday at a hearing featuring the case.

“He’s an innocent man, and we are very close to killing him for something he did not do,” said Wharton.

Wharton is perhaps – alongside Roberson’s attorney, Gretchen Sween – the inmate’s most vocal advocate. On Tuesday, the detective turned Methodist pastor learned the inmate had included him on his list of witnesses should the execution proceed.

“There’s a part of me that wants to just run away from that. I don’t want to be there, I don’t want to watch it happen,” Wharton told CNN. “But it is, again, it’s a moment that I owe him. If he’s asked me to be there, I owe him that much.”

State lawmakers lobby for a stay

Wharton is now one of many supporters of Roberson: More than 30 scientists and medical experts who agree with the doctors cited by the inmate’s attorneys, a bipartisan group of more than 80 Texas legislators, autism advocacy groups and author John Grisham have all called for mercy, a fervent movement that mounted strong opposition to the execution in recent days.

Support in the legislature includes members of the Texas Committee on Criminal Jurisprudence, which on Wednesday held a hearing highlighting Roberson’s case, calling Wharton, Sween and others who gave voice to the doubts surrounding the shaken baby syndrome diagnosis.

The hearing was ostensibly about Texas Article 11.073, a state law commonly referred to as the “junk science writ,” which was meant to give defendants a way to challenge their convictions when there was new scientific evidence unavailable at the time of their trial.

The committee voted Wednesday to subpoena Roberson, calling on him in the motion to “provide all relevant testimony and information concerning the committee’s inquiry.” Though the committee is not totally confident that Roberson’s execution will be delayed, they are hopeful, a source with knowledge of the proceedings told CNN.

Last week, the appeals court ordered a new trial for a man sentenced to 35 years in prison for his conviction of injury to a child in a case that also relied on a shaken baby syndrome argument.

Roberson’s supporters believe he, too, should benefit from this law, which “was meant exactly for cases like this one,” the committee said in a letter brief to the Texas Court of Criminal Appeals.

The committee asked for a stay of execution in Roberson’s case while the legislature considered making changes to it in the coming legislative session. But the appeals court denied Roberson’s latest appeal on Wednesday, rejecting it on procedural grounds “without reviewing the merits of the claims raised.”

Committee member Leach expressed hope the governor and parole board were listening to the hearing, “because the law that the legislature passed and our governor signed into law is being ignored by our courts, and all we’re seeking to do here is to push the pause button to make sure that it’s enforced.”

Diagnosis focus of courtroom debate

Roberson’s attorneys are not disputing babies can and do die from being shaken. But they contend more benign explanations, including illness, can mimic the symptoms of shaking, and those alternative explanations should be ruled out before a medical expert testifies with certainty the cause of death was abuse.

Shaken baby syndrome is accepted as a valid diagnosis by the American Academy of Pediatrics and supported by child abuse pediatricians who spoke with CNN. The condition, first described in the mid-1970s, has for the past 15 or so years been considered a type of “abusive head trauma” – a broader term used to reflect actions other than shaking, like an impact to a child’s head.

Criminal defense lawyers also have oversimplified how doctors diagnose abusive head trauma, child abuse pediatricians say, noting many factors are considered to determine it.

Still, the diagnosis has been the focus of debates in courtrooms across the country. Since 1992, courts in at least 17 states and the US Army have exonerated 32 people convicted in shaken baby syndrome cases, according to the National Registry of Exonerations.

Child abuse pediatricians such as Dr. Antoinette Laskey, chair of the American Academy of Pediatrics’ Council on Child Abuse and Neglect, dispute these statistics. She pointed to a 2021 paper that found just 3% of all convictions in shaken baby syndrome cases between 2008 and 2018 were overturned, and only 1% of them were overturned because of medical evidence. The thoroughness of that study, however, has been called into question.

“I don’t know what to say about the legal controversy,” Laskey told CNN of the courtroom debate (She did not speak to Roberson’s case). “This is real, it affects children, it affects families … I want to help children; I don’t want to diagnose abuse: That’s a bad day.”