The infamous photograph of Lee Harvey Oswald holding a rifle in his backyard would have been nearly impossible to fake, according to a new analysis by a Dartmouth College professor.

Oswald, who was shot to death days after being charged with the 1963 assassination of President John F. Kennedy, claimed the photo of him holding a rifle in one hand and Marxist newspapers in the other had been doctored. Over the years, many others have pointed out what appear to be inconsistent lighting and shadows.

But Hany Farid, director of the Neukom Institute for Computational Science at Dartmouth, said the shadows are exactly where they should be.

"You can never really prove an image is real, but the evidence that people have pointed to that the photo is fake is incorrect," Farid said Thursday. "As an academic and a scientist, I don't like to say it's absolutely authentic ... but it's extremely unlikely to have been a fake."

Farid, whose work using digital forensic tools to analyze images often has been used by law enforcement, said he has been getting requests from conspiracy theorists to analyze the photo for years. He said he held off until he had the appropriate software to create three-dimensional models of Oswald's head and surroundings.

With the modeling software, he was able to show that a single light source could create both a shadow falling behind Oswald and to his right and one directly under his nose. Farid admits even he was skeptical before starting his research.

"When I looked at the photo, I didn't understand it. I didn't understand the shadows, and I do this for a living," he said.

But Farid's latest finding, which will be published in the journal Perception, is in keeping with his earlier research that showed the human visual system does a poor job at judging whether cast shadows are correct, he said.

"It turns out we're really bad at it. Even though our visual system is very, very good ... we are really bad at judging shadows," he said. "I'm bad at it and this is what I do for a living."

He spent about two months off and on analyzing the Oswald photo.

"I felt because it's the Kennedy assassination and because there's so much history about this, you really want to answer this correctly," he said. "You don't want to make a mistake on something of this magnitude."