A Texas judge has blocked the execution of the first man to be put on death row in the US for murder charges related to "shaken baby syndrome", less than two hours before the capital punishment was due to be carried out.

Robert Roberson, 57, was sentenced to death in 2003 for the death of his two-year-old daughter, Nikki Curtis, after a post-mortem examination concluded she died of injuries from abuse.

Roberson and his lawyers have long maintained the child died of complications from pneumonia.

Following his stay of execution, Roberson voiced his shock and thanked his supporters, US media reported.

The prisoner was due to be executed at 18:00 local time (23:00 GMT) on Thursday.

But only 90 minutes beforehand, a Travis County judge issued a temporary restraining order to stop it going ahead, so that Roberson could testify in a hearing at the state legislature next week.

The decision came after a panel of the Texas House of Representatives issued a highly unusual subpoena for Roberson late on Wednesday, hoping that authorities would have to send him to appear at a hearing on 21 October.

A bipartisan group of 86 Texas lawmakers, dozens of medical and scientific experts, attorneys and others - including best-selling author John Grisham and pro-death penalty Republicans - have all called for Roberson to be pardoned.

The group argued that the conviction was based on outdated science, before authorities gained a proper understanding of "shaken baby syndrome".

"In Robert’s case there was no crime and yet we’re about to kill somebody for it in Texas," Grisham told reporters in September.

Roberson's lawyers have also argued that his autism - which was undiagnosed at the time of Nikki's death - was used against him after police and medical staff became suspicious at the lack of emotion he displayed.

Autism can affect how a person communicates with others.

In a statement reported by the BBC's US partner CBS News, Roberson gave his reaction to the judge's intervention, praising God and thanking his supporters.

"He was shocked, to say the least," Texas Department of Criminal Justice spokesperson Amanda Hernandez told the Associated Press.

Shortly after the Travis County judge issued the last-minute reprieve on Thursday, the US Supreme Court declined to intervene to cancel the execution outright.

In a statement about the decision, Supreme Court Justice Sotomayor, a liberal, said it was up to Texas Governor Greg Abbott whether to stop the execution.

Meanwhile, the Texas attorney general has filed an appeal against the temporary restraining order.

Roberson's supporters include Brian Wharton, the lead detective who investigated the incident in Palestine, Texas.

“I will forever be haunted by the role I played in helping the state put this innocent man on death row,” Mr Wharton was quoted as saying by the Associated Press.

“Robert’s case will forever be a burden on my heart and soul.”

Earlier this week, Texas's Board of Pardon and Paroles denied Roberson's clemency petition, voting 6-0 against recommending that his death sentence be delayed or commuted to life in prison.

Governor Abbott could have also granted a one-time 30-day reprieve. He has only done so once in nearly a decade in office. Roberson recently urged Abbott to "do the right thing" because "I'm innocent".

Roberson was one of two prisoners scheduled to be executed in the US on Thursday. In Alabama, 36-year-old Derrick Dearman was put to death after admitting to killing five people with an axe and gun in 2016.

What happened to Roberson's daughter?

According to Roberson's account, his daughter fell out of bed on 31 January 2002.

Hours later, he said he realised she was not breathing and took her to an emergency room, where she was pronounced dead.

Court documents show medical staff immediately suspected abuse, because of bruises on her head, brain swelling and bleeding behind her eyes.

He was arrested and charged with capital murder the next day. An autopsy determined she died of blunt-force head trauma and her death was ruled a homicide.

Roberson's lawyers have noted that Nikki was prescribed medicines that are no longer given to children because they can cause serious complications.

They have argued that the medication, and her fall, could have ultimately killed her.

"Shaken baby syndrome" - now called abusive head trauma - is usually diagnosed after finding evidence of retinal haemorrhage, brain swelling and bleeding in the brain.

While the diagnosis is broadly accepted by the medical community, a recent report highlighted the need to thoroughly examine other causes before concluding injuries were due to abuse.

In 2023 an appeals court agreed there was insufficient evidence to overturn Roberson's conviction. The Supreme Court declined to hear his case.