The niece of the Labour MP Quentin Davies told police that she killed a man within hours of meeting him after he dared her to cut his throat during a drunken sex game.

Jessica Davies, 28, is under formal investigation on suspicion of murdering Olivier Mugnier at her Paris flat last weekend. After allegedly stabbing him, she tried to stem the flow of blood from his throat.

Ms Davies, who had consumed large quantities of alcohol, cannot recall the events that led to the 24-year-old Frenchman’s death.

She initially told detectives that they had dared each other to inflict wounds with a letter opener when she stabbed him in the chest and throat, according to a police source.

French police say they are treating her comments with caution because she was drunk and psychologically fragile. Ms Davies was remanded in custody in Versailles women’s prison, west of Paris, this week.

She told a French judge that she wanted to be jailed “to think about what had happened”, according to Le Parisien newspaper. Officers are investigating a theory that the “dare” was part of an extreme sex game. Ms Davies rang the emergency services in the early hours of Sunday as Mr Mugnier lay on the floor.

When officers arrived she was kneeling naked beside him and trying to stem the flow of blood from his neck. Mr Mugnier died about 45 minutes after the emergency services arrived.

Ms Davies has been remanded in custody on suspicion of voluntary homicide without premeditation. The offence carries a maximum sentence of 30 years in prison.

French authorities said Ms Davies had not known Mr Mugnier until they met in a bar last Saturday. She invited him to spend the night at her flat in Saint-Germain-en-Laye, a wealthy Paris suburb. Ms Davies was found to have 2.20g of alcohol in her blood and may have consumed “other substances”, according to police.

French police said that she would have psychiatric tests as part of the inquiry. A police source said: “She told us that she had been in a very bad way.” Ms Davies is reported to have taken to drinking heavily after splitting up with her French boyfriend recently. Neighbours say she began inviting men back to her flat regularly. One said they had complained to her because she held noisy parties with her boyfriends.

A French police source dismissed reports that Ms Davies could have been inspired by Meredith Kercher’s murder in Perugia, Italy. Although there are similarities between the two cases, the source said that there was no evidence of a copycat killing.

Mr Davies, 63, MP for Grantham and Stamford, defected to Labour from the Conservatives in June of this year.

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