A Texas man with a history of violence against women was put to death Wednesday for the abduction, rape and murder of a suburban Houston community college student over 20 years ago.

Larry Swearingen, 48, who argued his conviction was based on junk science, received a lethal injection at the state penitentiary in Huntsville for the December 1998 killing of 19-year-old Melissa Trotter.

She was last seen leaving her community college in Conroe, and her body turned up nearly a month later in a forest near Huntsville, about 70 miles north of Houston.

Swearingen, who had always maintained his innocence in Trotter’s death, was the 12th inmate put to death this year in the U.S. and the fourth in Texas, the nation’s busiest capital punishment state. Eleven more executions are scheduled in Texas this year.

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Prosecutors said they stood behind the “mountain of evidence” used to convict Swearingen in 2000. They described him as a sociopath with a criminal history of violence against women and said he even tried to get a fellow death row inmate to take the blame for his crime.

Swearingen had long tried to cast doubt on the evidence used to convict him, particularly claims by prosecution experts that Trotter’s body had been in the woods for 25 days. His longtime appellate attorney, James Rytting, said at least five defense experts concluded her body was there for no more than 14 days, and because Swearingen had been arrested by then on outstanding traffic violations, he couldn’t have left her body there.

Swearingen, who also was represented by the Innocence Project, had previously received five stays of execution. He was put to death after the U.S. Supreme Court rejected his final appeal, which focused on allegations prosecutors used “false and misleading testimony” related to blood evidence and a piece of pantyhose used to strangle Trotter.

Kelly Blackburn, the trial bureau chief for the Montgomery County District Attorney’s Office, which prosecuted Swearingen, said the killer’s efforts to discredit the evidence were unsuccessful because his experts’ opinions didn’t “hold water.”

“I have absolutely zero doubt that anybody but Larry Swearingen killed ... Melissa Trotter,” he said.

Blackburn said Swearingen killed Trotter because he was angry that she had stood him up for a date. At the time of Trotter’s killing, Swearingen was under indictment for kidnapping a former fiancée.

“Lord, forgive them,” Swearingen said after the warden asked if he had a final statement. “They don’t know what they’re doing.”

Then as the lethal dose of pentobarbital began, he said he could “hear it” going into a vein in his arm, then that he could taste it.

“It’s actually burning in my right arm. I don’t feel anything in the left arm,” he said.

Almost immediately, he took a short breath, then started to snore quietly. He stopped moving.

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He never opened his eyes and never looked at the witnesses who were there on his victim’s behalf, including her parents, who watched through a window just a few feet from him.

At 6:47 p.m. CT — 12 minutes after the lethal dose started — Swearingen was pronounced dead.

The Associated Press contributed to this report.