HOUSTON (AP) — The Texas Board of Pardons and Paroles on Wednesday denied a request for clemency for a man who this week could be the first person in the U.S. executed for a murder conviction tied to the diagnosis of shaken baby syndrome .

The parole board voted to not recommend that Robert Roberson’s death sentence be commuted to life in prison or that his execution be delayed. The decision is a major setback for efforts by Roberson's attorneys and a diverse coalition of individuals and groups to stop his lethal injection on Thursday. Roberson, who has long proclaimed his innocence, has few options left.

Gov. Greg Abbott can only grant clemency after receiving a recommendation from the board. Abbott does have the power to grant a one-time 30-day reprieve without a board recommendation.

But in his nearly 10 years as governor, Abbott has halted only one imminent execution, in 2018 when he spared the life of Thomas Whitaker . Earlier Wednesday, the Texas Court of Criminal Appeals denied another request from Roberson to stay his execution. Roberson’s attorneys have asked the U.

S. Supreme Court to stay his execution. Roberson, 57, was condemned for the 2002 killing of his 2-year-old daughter, Nikki Curtis, in the East Texas city of Palestine.

“We urge Governor Abbott to grant a reprieve of 30 days to allow litigation to continue and have a court hear the overwhelming new medical and scientific evidence that shows Robert Roberson’s chronically ill, two-year-old daughter,.