One is art, one is vandalism - but which is which?

But to the art collector whose painting she modified, Sam's act was nothing more than vandalism.

Yesterday the argument came to court, where Sam is being sued for more than 2 million by the owner of the painting - part of a tryptich entitled Phaedrus by the contemporary American artist Cy Twombly.

A Cambodian-born Frenchwoman, Sam, 30, was arrested in July after smearing lipstick over the painting during an exhibition dedicated to Twombly's work in Avignon in southern France.

Her trial, which opened in Avignon yesterday, came three days after a drunken gang broke into the Muse d'Orsay in Paris and punched a hole in a painting by the French Impressionist Claude Monet, sparking a debate about security in French museums.

Sam, who claims to be an artist herself, is being sued by the owner of the painting, art collector Yvon Lambert, who organised the exhibition of Twombly's work.

The young artist said she was overcome by the power of Twombly's work and issued a statement before the court case, distancing herself from the attack on the Monet painting.

"On the one hand you have a revoltingly bestial act of cruelty, on the other a pure, intense act of love. Rindy's gesture was an artistic act provoked by the power of art," her statement said.

"I take responsibility for my act. This white canvas inspired me. I am told it is forbidden to do such things, but it was totally spontaneous," it continued. "I just gave a kiss. It was a gesture of love; when I kissed it, I did not think it out carefully, I just thought the artist would understand."

Her lawyers, Patrick Gontard and Jean-Michel Ambrosino, asked for her to be acquitted, arguing that her gesture was not one of intended violence.

However, Eric Mezil, the director of the Lambert Collection, described her action as "rape" of a work of art.

"She speaks of love, but it is rape. She must understand the concept of an artist's intellectual ownership," he said.

Agnes Tricoire, the lawyer for the plaintiffs, argued that the kiss was "as aggressive as a punch", causing damage that was just as difficult to restore. She said: "I do not share [Ms Sam's] vision of love. For me love requires the consent of both sides. I expect compensation for my clients, the artist Cy Twombly, whose work has been altered, the Lambert collection, whose exhibition was ruined by this business, and Mr Lambert, owner of the work vandalised by Miss Rindy Sam."

The court will give its verdict next month.

HISTORY OF ART ATTACKS

ART vandalism, mindless or otherwise, is nothing new. Monet's painting, Le Pont d'Argenteuil, was damaged this week when a drunken gang broke into a Paris museum and punched a hole in it.

Marcel Duchamp's 2 million urinal, on display in Paris, was smashed by Pierre Pinoncelli, 77, in his second attack. In 1993 he urinated in it while it was on display.

The painting of Christ of St John of The Cross, by Salvador Dali, has twice been attacked by vandals in Glasgow. In 1961 it was slashed with a knife and later an air rifle was fired at it.

Copenhagen's Little Mermaid statue has been attacked at least ten times in the past 50 years, having its head cut off twice and been repeatedly covered in paint.

In 1991, Michelangelo's statue of David was hit with a hammer, damaging the toes.

And somebody fired a sawn-off shotgun at his painting of The Virgin and Child with St Anne and St John the Baptist in London in 1987.

Britain's biggest single art loss probably came when fire hit a London warehouse and destroyed more than 100 works owned by advertising guru Charles Saatchi in 2004.