Florida executed a man on Wednesday who was convicted of murdering two relatives to prevent one of them from testifying against him in a burglary trial.

Robert Hendrix was pronounced dead at 6:21 p.m. at Florida State Prison in Starke, shortly after the lethal injection procedure began. He made no final statement.

Hendrix was convicted of the 1990 murders of Elmer and Michelle Scott at their Lake County home.

Prosecutors said Hendrix killed the couple because Elmer Scott intended to testify against him. But Hendrix's attorney said no forensic evidence links his client to the murders, and the witnesses against him were unreliable.

Hendrix was the fourth person executed in Florida this year and the 16th since Gov. Rick Scott took office in 2011.

Evidence in the case showed Hendrix shot Scott in the face in his trailer home, hit him in the head with the gun and stabbed him in the neck the night before Hendrix's trial in the armed burglary case was to begin in August 1990. Hendrix then used a knife to cut the throat of Scott's wife, Michelle, who fought back before Hendrix shot her three times, they added.

Scott had already made a plea deal with prosecutors in the armed burglary case in which he and Hendrix broke into a house but only Scott was caught. His cooperation led investigators to arrest Hendrix. In the weeks leading up to his trial, prosecutors say, Hendrix told friends he would kill Scott rather than return to prison

Prosecutors say that on the night of the murders, Hendrix's live-in girlfriend Denise Turbyville drove him from Orange County, where they lived, to the Scotts' trailer in neighboring Lake County and dropped him off.

Michelle Scott welcomed Hendrix into the trailer, and told him Elmer Scott was in the bathroom shaving and would be out shortly. When Elmer Scott came out, Hendrix asked to use the bathroom. When he left the bathroom, Hendrix fired shots at Elmer Scott and then grabbed a knife and attacked Michelle Scott, according to prosecutors.

Turbyville pleaded guilty to two counts of second-degree murder and was sentenced to 75 years in prison. Another witness against Hendrix, Roger LaForce, was a confidential informant for a narcotics task force and stood to gain a lighter sentence for his assistance, Hendrix's attorneys say.

Hendrix attorney Harry Brody also said the presiding judge had a conflict of interest, Hendrix's trial lawyer was ineffective at presenting mitigating circumstances during sentencing and that Hendrix was shackled during his trial, leading jurors to a biased impression that he was dangerous.

During sentencing, Hendrix's attorneys failed to call witnesses who could have testified that Hendrix was regularly beaten by his father and had a serious drug addiction, factors that could explain his unbalanced mental state, according to court papers filed by Hendrix.

Earlier Wednesday, the U.S. Supreme Court denied Hendrix's last-minute request for a stay without comment. He ate a last meal of pork chops, sausage gravy and biscuits, German chocolate cake and a soft drink, state corrections officials said.