Defense attorneys argued Tuesday that a former FBI agent's conviction in the 1982 mob-related killing of a gambling executive should be tossed out because the agent never touched the murder weapon.

There was a four-year statute of limitations on prosecuting someone for second-degree murder at the time of the killing, though that time limit can be voided by the involvement of a gun. Because John Connolly had no direct connection to the gun in the case, his 2008 conviction cannot stand, the former agent's attorney Manuel Alvarez told a state appeals court

"You have to allege physical possession of the firearm during commission of the felony," Alvarez told a three-judge panel of the Third District Court of Appeal. "We don't have that in this case. We all know John Connolly did not shoot anybody."

Connolly was 1,500 miles away when a hit man gunned down 45-year-old John Callahan in South Florida, but prosecutors successfully argued at trial that information he provided to mobsters led to Callahan's death.

Connolly, 70, was convicted of second-degree murder in the killing of Callahan by a hit man linked to Boston's Winter Hill Gang. Its chieftains include James "Whitey" Bulger — a 16-year fugitive on the FBI's most-wanted list — and Stephen "The Rifleman" Flemmi, who is imprisoned and testified against Connolly. Flemmi said Connolly tipped the mobsters in a phone call weeks before the slaying that Callahan was likely to become an FBI informant against the gang.

Prosecutor Joel Rosenblatt said that Connolly, as an FBI agent, was almost certainly armed when he made that phone call and that the crime culminating in Callahan's shooting began at that moment. They contend that possession of any gun by Connolly, including his FBI service weapons, overcomes the statute of limitations.

Citing trial testimony, Rosenblatt quoted Connolly as telling the gangsters that if Callahan "spills the beans, we are all going to prison for the rest of our lives." They were concerned that Callahan would tell investigators about their involvement in the 1981 killing of an Oklahoma businessman.

Two of the appeals judges appeared sympathetic to the prosecutors. Judge Leslie Rothenberg said the jury in Connolly's trial found that he was a "principal" in the slaying and therefore just as guilty as the admitted hit man, John Martorano, and the two Winter Hill leaders who ordered the killing.

"The jury found that he was a part of that homicide," Rothenberg said. "The state says that this was an ongoing offense until the trigger was pulled."

The body of Callahan, president of World Jai-Alai, was found stuffed in the trunk of his Cadillac at Miami International Airport in August 1982. Trial testimony showed that Connolly was in Massachusetts when Callahan was slain; Connolly wasn't indicted in the case until 2005.

Connolly, once a highly decorated Boston FBI agent, is serving time in a North Carolina federal prison for a corruption conviction stemming from his dealings with the Winter Hill Gang. He is scheduled for release on June 28, 2011, but would immediately begin serving a 40-year sentence in the Florida murder case if his conviction stands.

The judges did not indicate when they would rule, but such cases typically take months after oral arguments. Whichever side loses also could appeal to the Florida Supreme Court for a final decision.

Martin Scorsese's 2006 film "The Departed" was loosely based on the Winter Hill Gang, with Matt Damon playing a crooked cop and Jack Nicholson as an Irish-American gangster similar to Bulger.