The Frenchwoman who shot dead Edouard Stern, the billionaire banker, was a venomous manipulator driven by hatred and greed and not by passion, as she claimed, a jury in Geneva was told yesterday.

Near the end of the trial of Cécile Brossard, 40, the prosecutors and lawyers for Mr Stern’s family sought to demolish her claim that her 50-year-old lover had tormented her into an uncontrollable passionate rage in his flat in Geneva in February 2005. She has described how, dressed as a dominatrix, she fired four pistol shots into him during a sex game in which he wore a latex suit and mask.

The pair, who had been in a tempestuous relationship for four years, were obviously tied by sex and mutual love, Daniel Zappelli, the prosecutor, said. “But it is not love that killed him. It was hate and money,” he said.

Ms Brossard’s mental state at the instant she pulled the trigger is the crux of the case, which has riveted the French and Swiss media and appalled members of the Continent’s old-money upper class.

She is charged with unpremeditated murder, which carries a maximum 20-year sentence. She and her lawyers are arguing that the act should be qualified as a crime of passion, which carries a minimum sentence of one year and maximum of ten.

Ms Brossard, a former shop assistant and escort girl, has told the court of her undying love for Mr Stern, explaining that he had goaded her into despairing rage by calling her a whore over $1 million that he had given her but threatened to take back.

“Of course I am 100 per cent guilty because I did it,” Ms Brossard told the 15-member jury on Monday. She described a relationship in which Mr Stern had tried to control every aspect of her life and used her to arrange sex for him with other women. “He put me under much pressure to find girls for him . . . He made me understand that I had nothing to do in his life, that I was too mediocre for him,” she said.

Pascal Maurer, Ms Brossard’s lawyer, told the court that she had been pushed to the limits by the way her lover toyed with her as his prey. “Edouard Stern was a hunter. What he liked was tracking his prey. Cecile Brossard was pretty game for him. Human game.”

The banker was a sexually perverse manipulator who forced Ms Brossard to round up male and female sex partners for him, the lawyer added. The prosecution sought to undermine Ms Brossard’s version by playing to the court telephone conversations, recorded by police after the killing, in which she was heard insisting on her innocence and scheming to throw investigators off her trail. She confessed after two weeks to killing the banker, whose powerful friends included Nicolas Sarkozy, the French Interior Minister at the time.

Marc Bonnant, summing up for the victim’s family, said that her story was a smokescreen. “This woman is venomous. She is not a liar. She is the lie,” he said. Ms Brossard had shown “incredible duplicity” when, ten days after killing the banker, she had asked his children to release to her the million dollars in her bank account that he had frozen before his death, Mr Bonnant said.

The prosecutor said that Ms Brossard had come within an inch of being tried for premeditated murder. His statement reflected what the Swiss media and commentators say is the odd handling of the case. Ms Brossard was originally charged with the more serious offence but it was dropped in February in what was widely seen as a compromise to limit the scandal that would emerge from that trial. Ms Brossard had been expected, in that event, to drag the reputations of French public figures into the proceedings.

The jury is expected to return a verdict late today.

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