Vjeran Tomic, a balding 49-year-old who is a skilled rock climber, arrived in a blue overcoat and sweatshirt for his trial in Paris where he faces up to 20 years in jail if convicted of the robbery.
He admitted to carrying out the heist after being arrested in May 2011 and compared himself to a famed thief from French literature as he spoke to reporters on Monday.
‘What role did I have? Arsene Lupin,’ he told reporters with a smile, referring to the sly but charming character who ransacked rich Parisians' homes in stories first published at the start of the 20th century.
Tomic and two alleged accomplices have been charged over the May 2010 robbery at the Modern Art Museum of five paintings by Henri Matisse, Pablo Picasso, Georges Braque, Ferdinand Leger and Amedeo Modigliani. All the artworks are still missing.
Tomic is suspected of cutting through a padlocked gate and breaking a window to get into the gallery, one of the most-visited museums in Paris on the banks of the Seine.
The museum's alarms had been awaiting repair for several weeks and Tomic is alleged to have somehow knocked out a security camera.
Three guards were on duty that night, but the paintings were only found to be missing from their frames just as the museum prepared to open to the public the next day.
When police arrested the Serb in May 2011, Tomic told them he had initially broken into the museum for Leger's ‘Still Life with Candlestick’ from 1922, not thinking he would also be able to steal another four.
Besides the Leger canvas, the other works stolen were Picasso's cubist ‘Dove with Green Peas’ from 1912 -- alone worth an estimated 25 million euros ($26.8 million) -- French contemporary Matisse's ‘Pastoral’ from 1905, Braque's ‘Olive Tree near Estaque’ from 1906, and Modigliani's ‘Woman with a Fan’ from 1919.
All but the Modigliani were hung in the same room in the museum, located in the well-heeled 16th district of Paris, which is run by the city and is home to more than 8,000 works of 20th-century art.
- 'Liked' paintings -
Tomic, who has a long criminal record of 14 previous offences, said he took them all because he ‘liked’ the paintings.
Authorities put the total value of the haul at 100 million euros ($107 million), but some experts said they were worth twice that, while admitting it would be impossible to sell such artworks on the open market.
The presiding judge at the trial on Monday, Peimane Ghaleh-Marzban, said the value of the masterworks was ‘far higher than their market value.’
They have still not been recovered.
Ghaleh-Marzban also criticised the security ‘failures’ which enabled the heist to be carried out with ‘disconcerting ease.’
The defendants face a 10-year jail term if convicted for the theft or re-sale of the artworks, but Tomic's sentence could be double that given his criminal record.
Athletically built and 1.90 metres (6 foot 2 inches) tall, he earned his nickname for clambering into posh Parisian apartments and museums to steal valuable gems and works of art.
Prosecutors claim he was spotted by a homeless man as he roamed around the museum in the days leading to the theft.
Police arrested him after receiving an anonymous tip and tracking his mobile phone. Surveillance cameras from the night of the heist recorded only one person entering through a window who could not be identified.
An art dealer who admitted to having the paintings for a short time said he dumped them in a garbage can, which authorities do not believe.
International police body Interpol put out an alert to its 188 member countries in the hope of recovering the five paintings, but so far they all remain missing.
There has been a spate of art thefts in Europe in recent years.
The most recent, in 2015, involved the theft of five paintings worth 25 million euros by renowned British artist Francis Bacon in Madrid.
Spanish police arrested seven people last year suspected of being involved in that theft.