David Pittman, 63, is set to be executed Wednesday for murdering his wife’s parents and their other daughter in May 1990.
STARKE, Fla. — A man from Florida, found guilty of murdering his estranged wife’s sister and parents and committing arson at their residence, is slated to be executed on Wednesday, marking the 12th execution in the state for 2025.
David Pittman, aged 63, is scheduled to be put to death by lethal injection beginning at 6 p.m. at Florida State Prison near Starke under a death warrant authorized by Governor Ron DeSantis. This Republican governor has issued more death warrants this year than his predecessors.
Pittman’s final appeal was rejected Tuesday by the U.S. Supreme Court.
Additionally, two more executions are arranged in Florida for this autumn. Victor Tony Jones is due to be executed on September 30 for the 1990 murders during a robbery, and Samuel Lee Smithers is scheduled for execution on October 14 for killing two women in 1996.
In 1991, Pittman was found guilty and received the death penalty for three counts of first-degree murder, according to court documents. The jury also convicted him of arson and grand theft.
At the time of the crimes, Pittman and his wife, Marie, were in the midst of a bitter divorce in May 1990. Investigators reported that he had previously made threats against her family.
According to trial evidence, Pittman severed a phone line at the parents’ home of his wife in Mulberry, Florida, where her father Clarence Knowles, 60, and mother, Barbara Knowles, 50, resided. Pittman fatally stabbed them along with their other daughter, 21-year-old Bonnie Knowles. He subsequently set their home on fire and stole Bonnie Knowles’ vehicle, which he also set ablaze. The family was discovered deceased 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.
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