Robert Roberson III has spent more than two decades on Death Row awaiting execution for killing his two-year-old daughter Nikki Curtis at his home in Palestine, East Texas

Robert Roberson III, 57, is on Death Row for killing his two-year-old daughter, Nikki Curtis (Image: KLTV)

A Death Row inmate has made an 11th-hour plea for mercy ahead of his execution, claiming autism put him behind bars.

Robert Roberson III has spent more than two decades awaiting capital punishment for killing his two-year-old daughter.

The 57-year-old was convicted of murdering Nikki Curtis at his home in Palestine, East Texas, in 2003, by the now largely discredited shaken baby syndrome (SBS).

Now Roberson’s lawyers are arguing a combination of his lack of emotion at the time of Nikki’s death, and the debunked medical hypothesis should see his case overturned.

On January 31, 2002, Roberson had taken Nikki to hospital informing staff she had fallen from her bed after a period of feeling unwell.

His daughter had significant head injuries along with bruises on her chin, cheek and jaw, as well as a subdural hematoma. A nurse described her as “limp and blue”.

A nurse described Nikki as ‘limp and blue’ when Roberson brought her into hospital (Image: Roberson Family)
Hospital staff called the police after becoming suspicious about Roberson’s seeming lack of emotion, and because of the nature of her injuries.

Now more than twenty years on, a shift in scientific views prompted his legal team to appeal and caused the main detective, who testified in the case, to change his mind about the guilty verdict.

The prosecutors along with the jury concluded Roberson had caused Nikki’s death by shaking her, rather than it being a result of a fall, and he was told he’d be executed. However, in the years that followed, doctors have refrained from attributing SBS as a reason for someone’s passing.

The scientist who put forward the idea openly admitted it was being misused to unjustly incarcerate innocent individuals. In 2012 he issued a warning, stating “we have gone badly off the rails”.

The way Roberson acted, which seemed lacking in remorse to the police, has now been viewed differently since his lawyers shared that he was diagnosed with autism while serving his sentence.

Roberson appeared to lack emotion, which raised suspicions from hospital staff (Image: KLTV)

The staff at the hospital thought he seemed emotionless when he responded to his daughter’s situation. His inability to explain her condition made them think he was lying to them.

Nikki had been sick in the week before her death and visited a local emergency room where she was prescribed Phenergan and sent home. After her condition doctors gave her more Phenergan and codeine.

The opioid codeine is now restricted from children under the age of 18, and Phenergan now comes with a warning for use with children.

The following night she had gone to sleep beside her father, who woke up to find her unconscious. Brian Wharton, a now retired detective who was involved in the case in 2002, was called to Palestine hospital after receiving reports of a mortally ill child being brought in.

Roberson was arrested by Wharton just hours after Nikki passed away, without the autopsy results. Roberson had a criminal record for burglary and theft, and had violated his parole before his daughter’s death.

Despite testifying against Roberson during the trial, Wharton’s view of the case outcome has changed over the years.

Wharton says he thought something went very wrong in Roberson’s case (Image: KLTV)
In an op-ed published by the Dallas Morning News just last week, Wharton wrote the state must halt his case before they make “a tragic, irreversible mistake”.

Wharton said: “I have thought that something went very wrong in Roberson’s case and feared that justice was not served. If there is no movement to correct this injustice, I fear myself and others will carry our guilt eternally.

“I have come to believe that Nikki died of accidental and natural causes. I am convinced that she was not murdered. Roberson is innocent.

“There was no crime. I believe this because the ‘science’ that was used to obtain Roberson’s arrest and conviction has changed drastically since his arrest.”

Roberson said he found no sign of violence in the home where Nikki had collapsed and didn’t look like she had been beaten.