A painting titled19,000 in
A Paris laboratory has claimed that a print from an index or middle finger on the canvas is almost certainly da Vinci's.
The print closely matches one from da Vinci's painting of St Jerome, currently held in the Vatican. The artist worked alone at the time, so the print is unlikely to be anyone else's.
It only becomes clear using infra-red scanning, but the print is in the blemish on the left edge of the work, level with the subject's brow line.
The CSI-style evidence was collected by Peter Paul Biro, who is credited with pioneering various techniques for authenticating artworks.
He also notes a partial palm print in the painting's neck, a painting technique which Leonardo used.
The work is thought to bear some resemblance to da Vinci's ink and chalk drawing, Portrait of a Woman in Profile, currently held in Windsor Castle.
The mystery artist seems to have been left-handed, as was da Vinci.
Carbon dating also suggests the right age (1440-1650) for the work, rather than it being 19th century. The girl's clothes and hair are consistent with this.
Martin Kemp, Oxford University's Professor of the History of Art, feels sure that the portrait was by the great artist. He has even written a_200_page book on the subject, yet to be published.
"All the bits fell into place like a well-made piece of furniture. All the drawers slotted in" Kemp told the Gazette.
The Paris laboratory's findings will also vindicate Pete Silverman, the painting's current owner.
Silverman has long suspected that the painting was in the style of a Florentine artist, and that the artist may have been Da Vinci.
Estimates for the piece now vary, but London dealer Simon Dickinson has suggested it could be worth £100m.