A Texas death row inmate was scheduled to be put to death Thursday for killing a 93-year-old woman at her home during a robbery a decade ago, though his lawyers sought a day earlier to have the execution delayed.

Clifton Lamar Williams was convicted of killing Cecelia Schneider, who was found by firefighters as they responded to a call about smoke coming from her home in Tyler, about 85 miles east of Dallas, in July 2005. Investigators later determined she had been beaten and stabbed before her body and her bed were set on fire.

If the death sentence is carried out, Williams, 31, would be the 10th inmate to receive a lethal injection this year in Texas. The state carries out the death penalty more than any other state, and has at least seven other executions scheduled in the coming months.

The U.S. Supreme Court refused in April to review Williams' case. But late Wednesday, defense attorney James Huggler asked Texas courts for at least a 60-day delay after the Texas Attorney General's Office disclosed that two witnesses at Williams' 2006 trial used incorrect statistics provided by the FBI when testifying about population and DNA probabilities.

Huggler said what wasn't clear was what effect the errors had on their analysis.

The revised figures "changed only slightly" from the original calculations and remain overwhelmingly against any claim that Williams is innocent, Smith County District Attorney Matt Bingham said in response to the filings.

"In this case, there is nothing extraordinary or compelling that requires reconsideration," he said.

Williams' lawyers had argued unsuccessfully in earlier appeals that his legal help at his trial was deficient. They also said Williams, who dropped out of school in the 12th grade, was mentally impaired and therefore ineligible for the death penalty.

Prosecutors said Williams broke into Schneider's home to get money to buy cocaine. Her missing car was found later that day, wrecked and abandoned. Williams, then 21, was arrested about a week later.

"His DNA and fingerprints were found in the victim's vehicle," Melvin Thompson, Williams' lead trial attorney, recalled Wednesday. "They had some significant evidence."

He said he didn't concede Williams' guilt but the "biggest objective in a capital case is to save the offender's life."

"It was frustrating, very frustrating," he said of the outcome. "I'm vehemently opposed to the death penalty. ... It's just vengeful killing."

Williams had been dating a woman who lived a few doors away from Schneider's home and had been seen in the neighborhood. Investigators said Williams led police to a pond where Schneider's purse that had contained about $40 was found, along with a knife from her kitchen that investigators believe was used to stab her.

During the trial, a pathologist testified that Schneider was stabbed four times, including in her heart and lungs, and was beaten and may have been strangled.

According to trial testimony, Williams told a psychiatrist he began smoking marijuana at age 15, started lacing it with embalming fluid, then moved on to cocaine by the time he was 17.

Defense attorneys told jurors at the trial that Williams became known on the streets as "Crazy C" after a stint in a mental health rehabilitation center.

Some death penalty states have had difficulties obtaining drugs for lethal injections, but Texas Department of Criminal Justice officials say they have enough pentobarbital, a powerful sedative, to accommodate all the scheduled punishments. They have refused to identify the drug provider.