In 2002, Robert Roberson found his two-year-old daughter, Nikki Curtis, unresponsive after she fell off a bed in the family’s house in the East Texas city of Palestine. Roberson took her to hospital, but a day later, the baby tragically died after succumbing to a head injury.

Within a year, Roberson, a labourer who is now 57, had been tried, sentenced and placed on death row for the killing of his daughter. Doctors and an autopsy report concluded that baby Nikki had died following severe abuse at the hands of Roberson – specifically from shaken baby syndrome.

The Texas Committee on Criminal Jurisprudence, which is reconsidering the lawfulness of Roberson’s conviction, issued a subpoena for Roberson to attend a hearing scheduled for Monday, October 21.

But Roberson very nearly didn’t make it to Monday. After a Texas state board rejected his clemency plea on Wednesday last week, he had been scheduled to receive a lethal injection on Thursday evening at 6pm local time (23:00 GMT) at the Texas State Penitentiary at Huntsville.

But in a dramatic turn of events, just hours before the execution was due to take place, a state judge in Texas issued a temporary restraining order halting it after a committee in the Republican-controlled state House of Representatives petitioned the court.

That decision triggered an avalanche of legal actions that continued late into the night. After Judge Jessica Mangrun’s decision was announced, the Texas Court of Criminal Appeals lifted the injunction and allowed the execution to proceed. But then the Texas Supreme Court weighed in, issuing a stay of execution.

Roberson, his lawyers, Texas lawmakers and even the lead detective on the original investigation say he is on death row for a crime he did not commit.

The science behind shaken baby syndrome has been brought into question in recent years. So what is it, and what happened in the case of baby Nikki?

Who is Robert Roberson and what was the evidence against him?

Originally from Wood County in Texas, Roberson had previously worked as a cook, construction worker, welder and labourer, according to the Texas Department of Criminal Justice.

The mother of Nikki, who has not been named, was reported to have been denied custody of the baby after her birth. The baby’s maternal grandparents granted Roberson custody.

The autopsy report for the baby cited bruises on her head, brain swelling and bleeding behind her eyes. Ultimately, the autopsy determined that Roberson’s daughter died of blunt-force head trauma, which doctors and police claimed was caused by shaking.

At his trial, witnesses including Roberson’s ex-girlfriend, her daughter and her niece, testified that they had seen him smack and shake his baby daughter “in anger”.

The hospital staff also reported that when Roberson brought his daughter to the local hospital, Palestine Regional Medical Center, he showed no reaction or emotion, further stoking suspicions of abuse.

“They viewed his inability to explain Nikki’s condition as a sign that he must be lying,” according to the website of the nonprofit legal organisation the Innocence Project, which is part of Roberson’s legal team. Roberson was diagnosed with autism after he was convicted, which his lawyers say explains his lack of reaction.

The Texas Court of Criminal Appeals halted his execution in 2016 but, in 2023, allowed the case to proceed with a new execution date after ruling that new evidence about his autism and other illnesses the baby was suffering at the time was not enough to overturn the conviction.

On Wednesday, Texas’s Board of Pardons and Paroles voted unanimously – 6-0 – against commuting his death sentence to life in prison.

Why do some people believe he is innocent?

Roberson’s supporters argue that his conviction was based on incomplete evidence and that information about the baby’s underlying health conditions was not properly considered.

Several people are campaigning for Roberson to be granted clemency – which covers anything from a full pardon to the sentence being commuted from death to life in prison – including Brian Wharton, the lead detective in Roberson’s case, who testified against him at trial.

When explaining why he changed his mind about Roberson’s guilt, Wharton has spoken about Roberson’s autism diagnosis, and said his team should have investigated further to rule out other reasons for the baby’s death.

In a video published on the New York Times YouTube channel on July 30 this year, Wharton spoke to Roberson for the first time in around 20 years through Plexiglass at the Texas State Penitentiary at Huntsville.

“I’m so sorry that you are still here. It’s our failure,” Wharton said to Roberson in the film.

“I helped put him here, and he didn’t deserve it,” Wharton’s voiceover played in the video against visuals of the men still talking in the prison’s meeting area. “No other possibilities for her injury were considered. I regret deeply that we followed the easiest path.”

Roberson has maintained his innocence for the two decades he has spent on death row. His lawyers argue that at the time of her death, baby Nikki had pneumonia that had turned septic. Court records also state that she was battling a slew of other health problems at the time of her death.

The Daily Mail reported that a week before her death, Nikki had been sick and was taken to a local emergency room where she was prescribed Phenergan, a drug used to treat pain, allergies and motion sickness that now comes with a warning for children her age.

The New Zealand Medicines and Medical Devices Safety Authority website warns: “Phenergan must not be used in children under 6 years of age, due to the potential for fatal respiratory depression”, among other dangerous side effects.

When her condition did not improve, she was given more Phenergan and codeine, an opioid that now can not be given to children under 18.

What are Roberson’s supporters calling for?

Supporters want clemency – which can mean anything from a full pardon to a reduction in his sentence – for Roberson. His lawyers want the court to reassess evidence that shows that Nikki’s death was due to her existing health issues.

A petition launched by the Innocence Project, calling on Texas Governor Greg Abbott to intervene in Roberson’s execution, had amassed 112,851 signatures as of 14:20 GMT.

Some 86 Texas lawmakers, both Republicans and Democrats, are also calling for clemency for Roberson. Democrat state representative of Texas, Joe Moody, wrote in a social media post on Friday, “We have to do all we can to pump the brakes before this stains Texas justice for generations.”

Others calling for clemency include parental rights groups, autism advocates, faith leaders and even the best-selling crime novelist, John Grisham. In a column for the Palestine Herald-Press, Grisham wrote: “Nikki’s death was a tragedy, not a crime.”

Detective Wharton has also called for the death penalty to be abolished in Texas and in the United States as a whole. If Roberson is executed, his death will be the fifth execution this year in Texas, and the 20th execution this year in the US, according to the Washington-based nonprofit the Death Penalty Information Center. It will be the first in a case of shaken baby syndrome.

While Texas law allows the state’s Governor Abbott to grant a one-time reprieve from the execution for 30 days, he cannot grant clemency unilaterally. He requires the board’s approval.

What is shaken baby syndrome?

According to the Mayo Clinic, shaken baby syndrome is a serious brain injury caused by forcefully shaking an infant or a toddler. It can manifest as a head injury, which was the conclusion of Nikki’s autopsy. This can cause permanent injury or brain damage or even the death of the infant.

Typically, injury by shaken baby syndrome is caused when “a parent or caregiver severely shakes a baby or toddler due to frustration or anger – often because the child won’t stop crying”, the Mayo Clinic says, adding it is not usually caused by bouncing a child or by minor falls.

The injury is caused because babies and young children often have weak neck muscles that cannot fully support the weight of their heads. When vigorously shaken, the fragile brain moves inside the skull. As a result, brain cells can be destroyed and oxygen supply to the brain can be blocked.

The hypothesis of shaken baby syndrome was first introduced by Norman Guthkelch, a British paediatric neurosurgeon, in a paper he wrote for the British Medical Journal in 1971. He discovered it when patients – young toddlers – were coming to him with bleeding on the surface of the brain but no external signs of abuse such as bruising. He wrote the paper to warn parents against shaking their children.

In a list of symptoms of shaken baby syndrome, the Mayo Clinic includes: irritability, difficulty staying awake, breathing problems, vomiting, paralysis or coma. In mild cases of the syndrome, the baby might seem OK soon after the injury, but could develop health or behavioural problems over time.

According to the National Center on Shaken Baby Syndrome, a US-based public charity, there are approximately 1,300 reported cases of shaken baby syndrome in the US every year. It adds that the syndrome is the leading cause of physical child abuse-related deaths in the US.

In 2009, the American Academy of Pediatrics changed the name of the injury to “abusive head trauma”.

Is shaken baby syndrome ‘junk science’?

While many paediatricians consider shaken baby syndrome to be a legitimate cause of injury, the American Association of Pediatrics acknowledged in an April 2020 publication that some in medical and legal circles had previously “misinterpreted” it.

Doctors now say that many other conditions can cause the symptoms linked to shaken baby syndrome. As a result, shaken baby syndrome is now considered a diagnosis of exclusion, which means that only when all other possible reasons behind the symptoms are first ruled out, it can be considered. 

British paediatric neurosurgeon Guthkelch died aged 100 in 2016. During his final years, he worked against the misinterpretation of his work. Technical writer and journalist Sue Luttner quoted him in her blog in 2012, saying: “I am frankly quite disturbed that what I intended as a friendly suggestion for avoiding injury to children has become an excuse for imprisoning innocent parents.”

To date, at least 32 people in 18 US states have been exonerated based on the increasingly discredited hypothesis, as well as witnesses taking back their testimonies, after being convicted for shaken baby syndrome, according to the National Registry of Exonerations.