The last known photo of American outlaw Jesse James is the real deal, according to the forensic expert who authenticated it.

Lois Gibson says the photo's owner, Sandy Mills, spent 12 years trying to convince people the man in the photo really was the infamous icon of the West who robbed banks, stagecoaches and trains. The forensic artist says the photo is in remarkably good condition. She estimates it could fetch $2 million to $4 million at auction.

"Ìt just seems so earthy, like they'd just stepped off the street," Gibson told As It Happens' Carol Off of the sepia-toned picture. And even more remarkably, she says the man sitting next to James is Robert Ford, a member of James's gang who eventually shot and killed him in 1882 to collect a bounty.

Gibson, who is in the Guinness World Book of Records for identifying more than 1,260 people through her forensic work, says she started the identification process by looking at all known photos of Jesse James. Initially, she tried to prove it wasn't him.

"But every single thing that I examined, I could not eliminate him." The man in the photograph shared all the same characteristics as Jesse James: the same different-sized eyes, the same distinctive eyebrows, everything. "It got down to every single detail that told me, oh my gosh, this is Jesse James."

Gibson says one of Mills' distant relatives may have had a relationship with James. "They probably harboured members of this gang at various times, and that's how they came to own this."