STARKE — A Florida man convicted of killing his estranged wife’s sister and parents and setting their house on fire was put to death Wednesday evening in what was a record 12th execution in the state this year.
David Pittman, 63, was pronounced dead at 6:12 p.m. following a lethal injection at Florida State Prison near Starke under a death warrant signed by Gov. Ron DeSantis. Florida’s Republican governor has signed more death warrants this year than any of his predecessors.
Pittman’s final appeal was rejected Tuesday by the U.S. Supreme Court.
So far, two more Florida executions are scheduled for this fall. Victor Tony Jones is set to die on Sept. 30 for the 1990 killings of two people during a robbery, and Samuel Lee Smithers is scheduled to be executed on Oct. 14 for the murders of two women in 1996.
Pittman was convicted and sentenced to death in 1991 on three counts of first-degree murder, according to court records. Jurors also found him guilty of arson and grand theft.
Pittman and his wife, Marie, were going through a contentious divorce in May 1990 when the killings occurred, and investigators say he had threatened to harm her family several times.
Trial testimony showed Pittman cut a phone line at the Mulberry home of his wife’s parents, Clarence Knowles, 60, and his wife, 50-year-old Barbara Knowles. Pittman stabbed the couple to death as well as their other daughter, 21-year-old Bonnie Knowles. Pittman then set their house on fire and stole Bonnie Knowles’ car, which he also set ablaze. The family was found dead on May 15 of that year.
A witness during his 1991 trial identified Pittman as the person seen running away from the burning car. A jailhouse informant also testified that Pittman had admitted to the killings. Jurors recommended the death penalty on a 9-3 vote.
Pittman’s most recent appeals focused on recent evidence indicating he suffers from intellectual disabilities, including an IQ in the low 70s, that was apparent at the time of the killings. His lawyers had argued that his execution would violate the Constitution’s protection against executing a person with severe mental problems.
Lawyers for the state disagreed, contending it came too late for Pittman to claim mental impairment from years earlier. The Florida Supreme Court, reversing a previous decision, had ruled in 2020 that such claims could not be applied retroactively.
Before Wednesday, 30 people had been executed in the U.S. in 2025, with Florida leading the way behind the flurry of death warrants signed by DeSantis. Prior to Pittman, the last person executed in Florida was 59-year-old Curtis Windom on Aug. 28, for his conviction in the 1992 murders of his girlfriend, her mother and another man.
Florida carries out executions with a three-drug injection — a sedative, a paralytic and a drug that stops the heart, according to the state Department of Corrections.
By CURT ANDERSON, Associated Press
