Robert Roberson, a Texas man convicted of killing his 2-year-old daughter, was set to be executed Thursday evening in a case that relied on a diagnosis of shaken baby syndrome that has since been questioned.

The execution, by lethal injection, set for anytime after 6 p.m. local time at a prison in Huntsville, Texas, would be the first of a person convicted in a shaken baby case, his lawyers said. It was moving forward after the state’s Board of Pardons and Paroles on Wednesday denied a request for clemency.

Mr. Roberson’s looming execution has drawn intense national scrutiny because of the role that the shaken baby diagnosis played in his conviction. His lawyers maintain that no crime was committed at all and have presented evidence and expert testimony that his daughter, Nikki, most likely died in 2002 from pneumonia exacerbated by medication she had been prescribed.

“It is not shocking that the criminal justice system failed Mr. Roberson so badly,” one of his lawyers, Gretchen Sween, said on Wednesday in response to the clemency denial. “What’s shocking is that, so far, the system has been unable to correct itself.”

The case focused renewed attention on shaken baby syndrome, a medical determination that abuse has caused serious or fatal head trauma that has played a role in criminal convictions for decades.

The American Academy of Pediatrics still recognizes the diagnosis, but it has come under scrutiny in recent years as some doctors and defense lawyers have challenged its reliability, particularly in cases where little other evidence of abuse exists.

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