Acclaimed movie director Jim Sheridan has stirred up a hornet’s nest with his claim that Abdelbaset al-Megrahi, the Libyan spy held responsible for blowing Pan Am Flight 103 out of the sky over the Scottish town of Lockerbie and killing 270 people in December 1988, was innocent.

The FBI officials in charge of the U.S. investigation as well as families and friends of the victims, 190 of whom were Americans, are especially troubled that the 65-year-old Sheridan is planning a feature film that will portray Megrahi—who died of cancer in May 2012 after being sprung from a Scottish prison on a controversial “compassionate release”—as blameless and wrongfully convicted of the crime.

“It kills me to think that they would go off and just tell some completely wrong story just because they like the way it sounds or there’s got to be another twist to it,” said Pan Am 103 widow Kathy Tedeschi, whose husband, Bill Daniels, was a passenger on the doomed flight. “There are too many people, like the FBI and Scotland Yard, who investigated this case, and I firmly believe they knew what they were doing and they got the right man.”

The Irish-born Sheridan, whose Oscar-nominated movies include In the Name of the Father and My Left Foot (for which Daniel Day-Lewis received the Best Actor award), told The Hollywood Reporter that he’s writing a screenplay with fellow Irish writer Audrey O’Reilly that will dramatize the experience of English physician Jim Swire, whose 23-year-old daughter Flora died on Pan Am 103. Swire treated the ailing Megrahi in jail, became convinced of his innocence and launched a still-ongoing campaign to clear the Libyan’s name.

“It was this weird thing where you think you’ve found the person who killed your daughter, and then Jim ended up in the cell looking after him—because he’s a doctor and the guy wasn’t well—and it’s obvious as the nose on your face that Megrahi didn’t do it,” Sheridan told The Hollywood Reporter, adding that Swire will be among his guests at the inaugural Dublin Arabic Film Festival, which Sheridan is staging in Ireland on May 8. The director’s Hollywood publicist said Monday he was traveling and unavailable for comment.

“Somebody should reach out to Mr. Sheridan and tell him he’s betting on the wrong horse,” said Frank Duggan, president of the nonprofit group, Victims of Pan Am 103 Inc., which represents relatives of the Americans killed in the Boeing 747’s explosion. “It would do a lot of damage,” added Duggan, who served as the family liaison for the President’s Commission on Aviation Security and Terrorism, which was established in response to the Lockerbie tragedy. “It keeps stirring the pot for all the crazies and deniers to say, ‘Aha! See, we were right!’”

Retired FBI agent Richard Marquise, who led the U.S. task force during the Lockerbie investigation and has written extensively about the case, said Sheridan seems to be aligning himself with “10,000 conspiracy theories, none of which has ever been tested in court. It’s a bunch of speculation and hypotheses and I feel bad that somebody is going to stake his reputation on it…Maybe that would sell a movie, but it wouldn’t be the truth.”

Retired FBI official Oliver “Buck” Revell, the bureau’s associate deputy director who rode herd on the American end of the Lockerbie investigation, told The Daily Beast: “As with our Hollywood filmmakers, truth has little or nothing to do with filmmaking and most documentaries. I am well satisfied to let the verdict and evidence that supported it stand. I do favor the investigation continuing, for I am certain that many of Megrahi’s superiors were complicit in this terrible crime.”

Megrahi, who when Flight 103 exploded was head of security for Libya’s national airline and allegedly a Libyan intelligence agent, was convicted of 270 counts of murder, and sentenced to life in prison, by a three-judge Scottish panel in January 2001. The evidence against him was circumstantial; a shopkeeper in Malta, where the bomb was allegedly put aboard the 747, identified Megrahi as the man who purchased the clothes that were found in the suitcase where the device had been concealed. Megrahi also had a business relationship with a Swiss company that manufactured the device’s timer, and he had traveled to Malta from Tripoli on a false passport—all damning pieces of evidence.

Megrahi consistently asserted his innocence. He appealed the verdict and lost, and a second appeal was abandoned after his defense team decided it might hamper legal efforts for an early release. Over bitter protests from the Obama administration, Scottish officials ultimately released him in August 2009, on the grounds that he was suffering from advanced prostate cancer and had only an estimated three months to live.

He was flown back to Libya on Muammar Qaddafi’s personal jet, accompanied by Qaddafi’s son Saif, and greeted by a triumphal celebration at the airport—a spectacle that enraged U.S. government officials and American relatives of the Lockerbie dead. He survived another three years, living out his last days in a posh villa in Tripoli. Ironically, he outlasted Qaddafi, who was killed in a popular uprising in October 2011, after being toppled from power and dragged bruised and bleeding through the streets.

Dr. Swire is among the more conspicuous supporters of Megrahi’s innocence and alternative theories of the Flight 103 disaster, which include claims that the explosion was the result of a drug deal gone bad, the work of Palestinian terrorists, or even retaliation by the Iranians, whose civilian airliner, Iran Air Flight 655, was shot down without justification by a U.S. Navy missile cruiser, killing all 290 people aboard, just 5 1/2 months before the Lockerbie disaster.

“Dr. Swire is not a credible figure,” Duggan said, adding that U.S. investigators initially liked the Iranian theory but were unable to find any evidence to corroborate it. “I’d like to say to Sheridan that you need to learn the facts before you assume that Megrahi was innocent. You need to look at other family members besides Dr. Swire. I don’t know any American family members who agree with him.”