Lois Gibson has won awards for her work with the Houston Police Department, recreating the faces of crime victims and analysing historical photos.

Only two images are universally agreed to depict Johnson, who died aged 27 in 1938. In 2008 Gibson stated that a picture of a man holding a guitar and standing with a friend was the blues icon. The guardians of his estate agreed - but many music commentators disputed the claim.

Now Gibson says that a picture discovered in a desk drawer, showing four people drinking in a bar, also features Johnson. It was found by retired lawyer Donald Roark, who purchased an antique desk at auction in 2013 and found the picture inside. He tells Chron.com: "I guess it was the hat - I chuckled and thought, 'That guy kinds of looks like Robert Johnson.'" Later he consulted with Gibson, who says: "99% of them I look at, and I don't laugh in their face, but I shrug it off."