David Pittman, 63, is set for execution by lethal injection on Wednesday, marking a record 12th execution in Florida this year. He was convicted of killing his estranged wife's sister and parents, and setting their house on fire.
Governor Ron DeSantis, who has authorised more executions this year than any of his predecessors, signed the death warrant for Pittman, whose final appeal was rejected by the U.S. Supreme Court on Tuesday.
The lethal injection at Florida State Prison near Starke is scheduled for 6 p.m.
Two further executions are already slated for Florida this autumn. Victor Tony Jones is due to die on 30 September for the 1990 killings of two people during a robbery, and Samuel Lee Smithers is scheduled for execution on 14 October 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, Florida 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 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 say his execution would violate the Constitution's protection against putting to death a person with severe mental problems.
Lawyers for the state disagreed, contending it is now too late for Pittman to claim mental impairment from years earlier. The Florida Supreme Court, reversing a previous decision, ruled in 2020 that such claims cannot apply retroactively.
“Pittman’s underlying intellectual disability claim is meritless. He was not intellectually disabled when he murdered the three victims in 1990 or when he went to trial in 1991,” the state attorneys told the U.S. Supreme Court.
Before Pittman, 30 people have been executed in the U.S. in 2025, with Florida leading the way behind the flurry of death warrants signed by DeSantis. The last execution in Florida was the Aug. 28 lethal injection of 59-year-old Curtis Windom, convicted of the 1992 murders of his girlfriend, her mother and another man.
Florida executions are carried out via a three-drug injection — a sedative, a paralytic and a drug that stops the heart, according to the state Department of Corrections.
