lling was caught on surveillance video

Howard was convicted of capital murder in the 2000 killing of Vickie Swartout, 42, who was shot once in the chest during a store robbery. Evidence presented at trial included store surveillance video that showed Howard shooting Swartout.

Howard, then age 20, took $114 and a carton of cigarettes from the store in the small, rural town of Silsbee, about 100 miles (160 kilometers) northeast of Houston, according to court records.

His attorneys have argued to the U.S. Supreme Court that Howard's execution should be halted because he is intellectually disabled. But the state said his attorneys haven't presented evidence showing he meets the requirements for a claim of intellectual disability. The court late Wednesday rejected Howard's appeal in a brief notice without elaborating.

In 2002, the Supreme Court had barred the execution of intellectually disabled people. But it has given states some discretion in determining intellectual disability.

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Defense files motions to stay execution because of drugs

In their filings in the Texas Court of Criminal Appeals, Howard's attorneys said they filed requests for information about the lethal dose of pentobarbital the Texas Department of Criminal Justice planned to use.

The attorneys said the department asked for a state attorney general opinion about whether it must disclose that information, but that opinion is not expected to be returned until after Wednesday.

Texas officials did not immediately return a request for comment Wednesday.

Florida leads nation in executions this year

Florida has carried out 16 executions so far this year, the most of any state. Most states that allow executions use lethal injection as their primary method.