TALLAHASSEE, Fla. — A federal appellate court on Monday temporarily stopped the execution of a drug trafficker convicted of killing a Florida state trooper with a pipe bomb.

What began as a routine traffic stop on Interstate 10 in rural north Florida quickly escalated into the killing of the trooper and launched a multi-state investigation that unraveled a major crack cocaine ring 21 years ago.

That chain of events was set to end with the execution Tuesday of South Florida drug trafficker Paul Augustus Howell, 47, for murdering Florida Highway Patrol Trooper Jimmy Fulford on Feb. 1, 1992.

The Atlanta-based 11th U.S. Circuit Court of Appeals, though, stayed the execution that was scheduled for 6 p.m. at Florida State Prison near Starke until it could hear the merits of Howell’s case. The Florida Supreme Court and Chief U.S. District Judge M. Casey Rogers both denied last-ditch pleas to stop the execution, but Rogers earlier Monday certified Howell’s appeal to the 11th U.S. Circuit.

Howell’s attorneys contend his trial lawyer, now a state circuit judge, had a conflict of interest and failed to find and present mitigating evidence that could have persuaded his jury to recommend a life sentence rather than the death penalty. His initial appellate lawyer then failed to present those arguments in federal court because she missed a filing deadline more than 10 years ago.

A former prosecutor said Fulford’s death likely prevented many more because the bomb inside a gift-wrapped microwave oven was intended to go off in a crowded Marianna housing complex.

On the day he died, Fulford had stopped Lester Watson for speeding in Jefferson County just east of Tallahassee in a car Howell had rented. The trooper then arrested Watson for driving without a valid license.

After sheriff’s deputies picked up Watson and a passenger, Fulford opened the package he’d found in the car’s trunk as he waited on the roadside for a tow truck.

A dispatcher, meanwhile, had called Howell to ask if he knew someone else was driving his rental car more than 400 miles away.

“By the time Jimmy Fulford knelt to open that microwave with his knife, Paul Howell knew that the car had been stopped,” prosecutor Thomas Kirwin told jurors in his closing argument. “But Paul Howell was in a killing mood.”

Fulford, a father of two, was killed instantly when the bomb exploded. His wife, Keith Ann, asked Circuit Judge F.E. Steinmeyer to condemn Howell to death at his sentencing hearing.

“He could have chosen to tell the dispatcher to tell Trooper Fulford not to open the package,” she told the judge. “What Paul Howell did was murder my husband in cold blood.”

Keith Ann Fulford said she would not be attending the execution and declined further comment. After Howell’s sentencing in 1995, Fulford’s wife said his execution would bring “some closure and justice,” but added: “It’ll never be over for me, even after he’s executed.”

Kirwin, now the state’s deputy chief financial officer for law enforcement, initially prosecuted Howell and other members of the drug ring known as the “posse” on federal charges as an assistant U.S. attorney.

Howell was convicted of drug trafficking in a Tallahassee federal court, where he received a life sentence. He was among 28 people who eventually were convicted or pleaded guilty to federal drug crimes as a result of the investigation triggered by Fulford’s death.

Kirwin then was in effect loaned to the state to help Assistant State Attorney Michael Schneider with Howell’s murder trial, which was moved to Pensacola because of extensive news media coverage about the case in Jefferson County. Howell was convicted of first-degree murder and making, possessing, placing, or discharging a destructive device or bomb. The jury voted 10-2 to recommend a death sentence.

“The thing that amazed me in the federal case is how broad this conspiracy was,” Kirwin recalled. “Death and guns really meant nothing to the folks we had charged.”

Prosecutors said Howell paid Watson $200 to deliver the bobby-trapped package to two women in the Panhandle town of Marianna with the intent of killing them because they knew too much about a drug-related murder in South Florida involving Howell’s brother, Patrick, and a cousin, Michael Morgan.

Howell and other Jamaican immigrants who formed the drug ring distributed crack from their Fort Lauderdale area base across Florida and into Alabama, Georgia and the Carolinas.

The booby-trapped microwave was intended for Yolanda McAlister, who had formed a relationship with Patrick Howell when he visited Marianna to deliver drugs, and Tammie Bailey, Morgan’s girlfriend, who also had a child with him.

Patrick Howell also was charged with Fulford’s slaying, but he pleaded no contest to first-degree murder and was sentenced to life in prison without parole for at least 25 years. That term, though, is consecutive to a life sentence he’s serving in federal prison for drug trafficking. Morgan also was sentenced to life on a federal drug conviction.

Watson pleaded guilty to second-degree murder and is serving a 40-year prison sentence.

Paul Howell’s court-appointed lawyer was Frank Sheffield, now a circuit judge in Tallahassee. He argued at trial that the state failed to prove Howell, a former Army electronics technician, made the bomb or was involved in drug dealing.

Prosecutors, though, showed jurors labels and pieces of a microwave oven found in Howell’s Lauderhill home, which experts testified were missing from the microwave that exploded. Other evidence found in his home included tools and bomb-making materials and an Army field manual on making explosives.

In a phone call, Paul Howell had asked Bailey what she and the baby needed, Kirwin said.

“She needed a microwave to heat the baby’s food,” Kirwin said. “He said ‘I’ll send you one.”’

Bailey and her baby certainly would have been killed and probably many others if the bomb had gone off in her apartment, Kirwin said. He said it was so powerful that bits of the bomb were found in the eastbound lanes of I-10 on the opposite side of a westbound exit ramp where it exploded.

“I don’t think Paul Howell gave two cents for how many people died,” Kirwin said. “He was just interested in saving his own bacon.”