According to a Gallup poll conducted for today's 50th anniversary of the assassination of U.S. President John F. Kennedy, 61 per cent of Americans believe other people besides Lee Harvey Oswald were behind the shooting.

The skepticism is understandable. The first investigation into JFK’s death, the Warren Commission, found that Oswald, a Marxist loner, acted alone. But a second investigation by the House Select Committee on Assassinations and commissioned by the U.S. House of Representatives, found Kennedy was killed as a result of a conspiracy and there was a high probability more than one assassin fired at him.

But while conspiracy theories abound, conclusive evidence to prove them is scarce. That's why the claims of a Toronto man have been studied and scrutinized by conspiracy theorists for the past 50 years.

Eyewitness to history

Norman Similas lived in Toronto and worked as a reporter and photographer for the Canadian Beverage Review. He was on assignment for the magazine in Dallas when Kennedy was shot.

He maintained that his brush with history began the day before the assassination. Similas told Liberty Magazine in 1964 that he met Jack Ruby at his Dallas nightclub. Two days after the assassination, Ruby murdered Oswald. In the same article, Similas also claimed that he met Vice President Lyndon Johnson. Hours after the assassination, aboard Air Force One with Jackie Kennedy at his side, Johnson was sworn in as the 36th president of the United States.

Similas claimed he was close to the presidential motorcade on the day Kennedy was shot. In the following day’s Globe and Mail, he’s quoted as hearing a “sharp crack” and seeing Kennedy’s head and hair "bathed in blood."

He was apparently an eyewitness to what many call the crime of the century. But Similas returned to Toronto with more than a story.

The mysterious photo

Like most people who were alive that fateful day, Norman Similas’s son Kirk remembers exactly where he was on Nov. 22, 1963.

"I was at public school at the time and my teacher announced that Kennedy had been assassinated in Dallas, Texas. And I piped up, 'Well my father's in Dallas, Texas!'”

When his dad returned, he talked about a photo he'd taken at Dealey Plaza that showed, in the background, the Texas School Book Depository where Oswald shot from. But in the sixth floor window – the sniper’s nest – Similas claims that his photo showed that there was not one, but two figures.

It was very convincing proof of a conspiracy, or at least it would have been if the photo had ever seen the light of day.

Kirk Similas says his father tried to get the photo published in the Toronto Telegram newspaper. But after leaving his negatives with a photo editor, they vanished. “It just went missing. And ever since, everyone's been looking for that photo,” he told CBC News.

Even the FBI looked for it. Similas says his father was interviewed by the RCMP at the request of the FBI after the photo was mentioned in the 1964 Liberty article. The photo never materialized.

Cloud of doubt

John McAdams, a political science professor at Marquette University in Milwaukee, Wis., runs a website dedicated to JFK conspiracy theories, and says there are holes in Similas’s story.

Before the photo vanished, McAdams says it was viewed by an Associated Press photo editor in Chicago. McAdams says the editor did not see two figures in the sniper’s nest and Similas, in trying to get his photo published, “was maybe projecting what he wanted to see in the photo."

Many of the researchers and conspiracy buffs who have heard Similas’s story want to believe it. They’re looking for something, anything, that could prove a conspiracy. McAdams says, for the most part, they don’t believe the story.

Norman Similas died in 2009. Kirk Similas says his father received phone calls and visits from conspiracy buffs right up until the end of his life. Despite the mounting doubt, and lack of proof, his father's story never changed.

"I'm sure that picture existed," Similas says. "It's gone missing."

Like so much surrounding the JFK assassination, the truth about what Norman Similas saw and photographed on that historic day remains a mystery.