PARCHMAN, Miss. -- Mississippi on Wednesday executed Joseph Daniel Burns for the 1994 stabbing death of a Tupelo motel clerk.

The 42-year-old was given a lethal injection Wednesday evening at the State Penitentiary at Parchman. Department of Corrections spokesman Kent Crocker said Burns was pronounced dead at 6:50 p.m. It was Mississippi's third execution this year.

Burns was convicted in 1996 and was sentenced to death for the slaying of Floyd Melvin McBride at the Town House Motel. Prosecutors said Burns stabbed McBride while an accomplice opened the motel safe, then the two men then fled with money from the safe.

Republican Gov. Haley Barbour denied Burns' request for clemency earlier in the day.

"I will not substitute my judgment for that of the courts, which have considered the matter," Barbour said.

Mississippi allows the death in cases where a person is convicted of murder along with another felony, such as robbery.

Burns had been scheduled to die at 6 p.m., but the U.S. Supreme Court asked the state Wednesday afternoon to delay the execution for "an hour or two" while justices reviewed issues raised by Burns' attorneys, including whether Burns was denied a mental evaluation.

State officials agreed to the delay.

Less than a half hour after the originally scheduled time, the stay was denied. Soon after the denial was announced, witnesses began to be escorted to the execution site.

Burns had spent Wednesday in a cell near the death chamber. He visited with his mother, three sisters and two daughters.

Burns did not initially request a last meal, but later changed his mind. Corrections Commissioner Chris Epps said Burns had roast beef and turkey sandwiches and a soft drink. Epps said Burns declined a sedative.

Burns' lawyers claimed in the petition to the U.S. Supreme Court that Mississippi judges should have allowed the inmate's expert to conduct a psychological evaluation that could have been used for clemency or appeals. Prison officials won't allow defense experts to have access to death row prisoners without a judge's order, the petition said.

"When Burns was denied access, he was denied his fundamental constitutional rights," the lawyers argued.

Burns' lawyers also claimed his attorney did not properly prepare for the sentencing phase of his trial. The Mississippi Supreme Court rejected a similar argument.

Mississippi Attorney General Jim Hood said in papers filed with the high court that Burns had plenty of time to file an appeal with the nation's highest court.

"By waiting until the last minute to file these actions no other conclusion can be reached other than petitioner is attempting by any means to delay his execution with the tardiness of his filings," Hood wrote.