London couple convicted of murdering nanny, burning her body in their backyard

London: A London couple delusionally obsessed with a boy-band star were found guilty Thursday of murdering their French nanny and burning her body on a bonfire in their backyard.

A jury at the Central Criminal Court convicted 35-year-old Sabrina Kouider and 40-year-old Ouissem Medouni after six days of deliberation.

The French couple denied killing Sophie Lionnet, though they admitted disposing of the body. Each defendant blamed the other for the death of the 21-year-old Frenchwoman.

Prosecutors say the pair killed Lionnet after becoming obsessed with the belief she was in league with Kouider's ex-boyfriend Mark Walton, a founding member of Irish boy band Boyzone.

Kouider was said to be obsessed with Walton and believed Lionnet was having an affair with him and helping him carry out a sex-abuse plot. She and Medouni, a banker, repeatedly beat and interrogated Lionnet in an attempt to make her confess.

Prosecutors said the couple starved the nanny, beat her with an electrical cable and tortured her by dunking her head under water. After killing her in a bathtub in September, they threw her body on a bonfire near Wimbledon in southwest London.

When neighbours called firefighters because of a pungent-smelling smoke, Medouni claimed the charred remains belonged to a sheep. Kouider collapsed in tears as the jury foreman delivered the verdicts, while Medouni hung his head. The pair will be sentenced June 26.

The victim's mother, Catherine Devallone, wept in court, and called her daughter's killers "monsters."

"These monsters repeatedly beat Sophie," she said in a statement. "They starved, tortured and broke her. They took away her dignity and finally her life. Our Sophie will soon be laid to rest. No god will ever forgive you both for what you have done to our daughter."

Aisling Hosein of the Crown Prosecution Service said, "Only Kouider and Medouni know exactly how they killed Sophie but the prosecution was able to prove that she died as a result of purposeful and sustained violence, and not by accident."

"They were both jointly involved and came up with a plan to try and destroy her body and escape responsibility for this horrendous crime for which they have been found guilty," she said.