A French woman who confessed to killing banker Edouard Stern after they had sado-masochistic sex and argued over $1 million was found guilty yesterday of murder, rather than the lesser charge of a crime of passion.

Judge Alessandra Cambi read out the verdict reached by the Geneva jury of six women and six men after a one-week trial that revealed sordid details of the relationship between the artist and Mr Stern, one of the richest men in France.

The jury's statement said that Cecile Brossard "acted with a certain determination" in killing her long-time lover and then cleaning up evidence of the crime and fleeing the country, checking her bank balance between flights.

"Her state of despair was not excusable," the jury said, rejecting calls from Brossard's lawyers to consider the death a crime of passion, which carries a shorter prison term.

Earlier yesterday, the 40-year-old defendant apologised to Stern's family in the packed courtroom, where Stern's ex-wife and Brossard's sister Delphine looked on. "I am not a thief," she said. "I am a woman still madly in love."

Stern, 50, was found dead in his Geneva luxury flat in March 2005. Four bullet wounds pierced the head-to-toe flesh-coloured latex outfit he wore from the night before.

Sex toys littered his bedroom full of millions of dollars worth of antiques. Ms Brossard admitted to having cleaned up the crime scene and thrown the murder weapon into Lake Geneva.

The 38th richest man in France, Stern counted President Nicolas Sarkozy and Socialist politician Laurent Fabius among his friends. He was once heir apparent to his father-in-law, Michel David-Weill of the investment bank Lazard Freres.