Having come within four days of execution in 2016, he has already exhausted appeals through Texas state courts and must now rely on the mercy of the Republican governor Greg Abbott who rarely grants clemency.

“Robert Roberson is an innocent father who has languished on Texas’s death row for 20 years for a crime that never occurred and a conviction based on outdated and now refuted science,” the prisoner’s lawyer, Gretchen Sween, said.

Pediatric doctors detected symptoms including brain swelling which at the time were considered to be certain proof of child abuse and violent shaking.

Leading scientists have questioned the reliability of shaken baby syndrome, both as a medical diagnosis and as a forensic tool in criminal prosecutions, pointing to more than 80 alternative causes that can explain the symptoms without violence having occurred.

The girl had been ill with a fever of 104.5F (40.3C) shortly before she collapsed, had undiagnosed pneumonia, and had been given medical pills that are no longer considered safe for children as they can be life-threatening.

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