A Florida man convicted of killing his estranged wife's sister and parents and setting their house on fire is scheduled to be executed Wednesday, a move that would mark the state's 12th execution of 2025.
David Pittman, 63, is to receive a lethal injection beginning at 6 p.m. at Florida State Prison near Starke under a death warrant signed by Gov. Ron DeSantis. The U.S. Supreme Court on Tuesday rejected Pittman's final appeal.
Pittman was convicted and sentenced to death in 1991 on three counts of first-degree murder, along with convictions for arson and grand theft, court records show. Prosecutors say the killings occurred in May 1990 while Pittman and his wife, Marie, were going through a contentious divorce.
Investigators allege Pittman cut the phone line at the Mulberry, Florida, home of his wife's parents, Clarence Knowles, 60, and Barbara Knowles, 50, then stabbed the couple and their other daughter, 21-year-old Bonnie Knowles, to death. He then set the house on fire and stole and burned Bonnie Knowles' car. The family was found dead on May 15, 1990.
During Pittman's 1991 trial, a witness identified him as the person running away from the burning car, and a jailhouse informant testified Pittman had admitted to the killings. Jurors recommended the death penalty on a 9-3 vote.
Pittman's most recent appeals centered on evidence his lawyers say shows he suffers from intellectual disabilities, including an IQ in the low 70s, that they contend were present at the time of the killings. His legal team argued the execution would violate the Constitution's protection against putting to death a person with severe mental impairment.
State attorneys disputed that claim, telling the U.S. Supreme Court that Pittman "was not intellectually disabled when he murdered the three victims in 1990 or when he went to trial in 1991." Florida's lawyers also argued that it is too late for Pittman to raise mental impairment claims now. In 2020 the Florida Supreme Court reversed an earlier decision and ruled that such claims cannot be applied retroactively.
Florida has become the leading state for executions in the nation this year, driven in part by a series of death warrants signed by Gov. DeSantis. Before Pittman, 30 people nationwide had been executed in 2025, and the state carried out the most recent execution on Aug. 28, when Curtis Windom, 59, was put to death for 1992 killings.
Two more executions are scheduled in Florida this fall. Victor Tony Jones is set to be executed Sept. 30 for the 1990 killings of two people during a robbery. Samuel Lee Smithers is scheduled for Oct. 14 for the 1996 murders of two women.
Florida's executions are carried out by a three-drug lethal injection protocol that begins with a sedative, followed by a paralytic agent and a drug that stops the heart, according to the Florida Department of Corrections. The state has said it will proceed with Pittman's execution following the denial of his final appeals.