Teresa Lewis spent her last days praying and singing hymns, but she appeared frightened and tense as she entered Virginia's death chamber.
Lewis, 41, died by injection at 9:13 p.m. Thursday at the Greensville Correctional Center in Jarratt, Va., according to The Associated Press.
Lewis' final words were a message for the daughter of the husband she had killed.
"I just want Kathy to know that I love her, and I'm very sorry," she said.
Her death brought an end to the debate over whether Lewis deserved to die, with supporters saying she was borderline mentally retarded, despite the prosecution's claim that she was the mastermind of her husband's and stepson's murders.
Her attorney, James Rocap III, said Lewis was peaceful before going to her death and had been praying and singing in the days leading up to her execution.
"We thought that we were supposed to be helping her, while she was actually helping us," Rocap said.
But when Lewis entered the death chamber to be strapped onto a guerney and injected with the lethal cocktail of drugs, her jaw was visibly clenched. She looked around tensely and appeared frightened, witnesses reported.
In the chamber with her were 14 corrections officers who assisted her onto the guerney and secured her to it with heavy leather straps.
Moments before her execution, Lewis asked if her husband's daughter -- her stepdaughter -- was near. She was. Kathy Clifton was in an adjacent witness room blocked from the inmate's view by a two-way mirror. Lewis then gave her final words of farewell to her.
As the drugs flowed into her body, her feet bobbed but she otherwise remained motionless. A guard tapped her lightly on the shoulder, reassuringly, as she slipped into death.
Lewis was sentenced to die for concocting a grisly plan to hire two hit men to kill her husband and stepson in October 2002. Lewis stood by while Julian Lewis and son Charles Lewis were shot at close range as they slept.
She had promised the killers a cut of a life insurance policy to carry out the murders. Both triggermen were sentenced to life in prison, and one committed suicide in 2006.
Despite the controversy surrounding her execution, the Supreme Court refused to hear her appeal earlier this week, and Virginia Gov. Bob McDonnell had denied her petitions for clemency.
On the website Save Teresa Lewis, run by supporters who tried to have her death sentence commuted, a message was posted in which Lewis thanked them for their work on her behalf. They also posted a farewell Lewis had recently written to fellow inmates.
"Man wants me to die, but I'm not worrying over this, I'm trusting Jesus," she wrote. She urged the prisoners to turn to Jesus promising, "He will forgive you of all your sins and He will bring you into His loving arms."