Sued Artist Insists He Didn't Make Multi-Million Dollar Painting

Peter Doig is a world-renowned artist in high demand by art collectors. His paintings have sold for as high as $25 million. Does his body of work include this desert scene? Doig, as quoted in the Seattle Times, says no:

“I said, ‘Nice painting,’ ” he recalled in an interview. “ ‘Not by me.’ ”

That's the problem. Robert Fletcher says that 40 years ago, while still a teenager, Doig was incarcerated for LSD possession at a juvenile prison in Canada. At the time, Fletcher worked as a guard there. He says that Doig painted the scene and sold it to him for $100.
As a Doig painting, it's potentially worth millions of dollars--but only if it's an authentic Doig painting. And Doig says that it's not his work. So Fletcher is suing Doig for $5 million and asking a US federal court to declare the painting authentic:

Art-law experts say they can’t recall anything like it, certainly not for a major artist like Doig.
“To have to disprove that you created a work seems somehow wrong and not fair,” said Amy Adler, a professor at New York University Law School.

Fletcher's case has great challenges. For one, there are no records indicating that Doig was ever imprisoned at the facility where Fletcher worked.