HOUSTON — A Texas state board on Wednesday declined to stop what could be the first execution in the U.S. in a case tied to the diagnosis of shaken baby syndrome, rejecting clemency pleas from a man whose claims of innocence have drawn wide support, including from Republican lawmakers and a detective who say the conviction was based on faulty science.

The parole board voted unanimously, 6-0, 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. All members of the board are appointed by the governor.

— The Associated Press