ITALIAN police are scrutinising two Renaissance paintings in an attempt to find the fingerprints of Leonardo da Vinci, a search that, if successful, could boost the paintings’ value to more than £70m each.

The hunt by a unit of the paramilitary carabinieri police aims to resolve a dispute over attribution of the oil paintings, La Madone de Laroque and Saint Catherine of Alexandria.

Art historians believe the madonna, bought by a collector at a French flea market for £142 a few years ago, is by Giampietrino, an artist known to have painted in Leonardo’s workshop in Florence in 1495-7. But several French experts argue that Leonardo himself, who set up the workshop late in his career, worked on the painting.

The Saint Catherine, which shows her martyrdom under torture, is also believed to be by Giampietrino. Studies have shown the tips of the artist’s fingers were used to create a soft-focus effect in several parts of the painting, a technique for which Leonardo is famous.

Sometimes using his blood, sweat and urine, Leonardo also blended the still malleable paint with his fingers and palms to create an effect in areas such as a face joining hair. The traces of his fingers are visible only from very close up.

In a project headed by the University of Chieti in central Italy and the Museo Ideale in Vinci, Leonardo’s birthplace near Florence, police have taken photographs of fingerprints over the past three nights. They cannot work by day as the paintings are on show at Chieti University.

“I’m used to working on the fingerprints of criminals, but the techniques are the same,” said Colonel Gianfranco de Fulvio of the carabinieri.

His men will compare any traces they find with a database of 200 incomplete fingerprints gathered in the past three years by the Vinci museum and the university’s Luigi Capasso, an anthropology professor. Capasso has reconstructed what he describes as Leonardo’s left thumbprint from Lady with an Ermine, a painting at the Czartoryski museum in the Polish city of Krakow.

The two paintings under study this weekend could be put up for sale if a Leonardo print is found. At stake are not only the millions that could be added to their value but also the reputations of art historians and museum directors.

View a gallery of Leonardo da Vinci's paintings

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