Couple who murdered nanny had 'folie a deux' psychosis, court hears

The murder of a French nanny bears all the hallmarks of a psychosis known as folie a deux, where a delusion is shared from one individual to another, a court heard. 

Sabrina Kouider, 35, and Ouissem Medouni, 40, were found guilty of killing Sophie Lionnet, 21, and burning her body in their garden. 

Folie a deux, or "madness of two", was apparent in the case, according to the judge, with depressive and borderline personality Kouider the driving force and weak Medouni the willing party.

Kouider collapsed in tears as the jury foreman returned the verdicts, while Medouni hung his head.

Miss Lionnet's mother Catherine Devallonne also wept as Judge Nicholas Hilliard QC said he was sure the allegations made against her daughter by her killers had "no truth whatsoever".

In the weeks leading up to her death in September last year, the couple beat, starved and tortured the shy 21-year-old au pair by dunking her head into water until she confessed to the supposed link to Mark Walton - a founding member of pop group Boyzone and Kouider's ex-boyfriend.

Having killed Miss Lionnet in the bath, the pair threw her on a bonfire in the garden of their home near Wimbledon, south-west London, as they barbecued chicken nearby.

When firefighters were alerted by neighbours to pungent-smelling smoke, Medouni tried to pass off the charred remains as a sheep.

And Kouider claimed to police that Miss Lionnet had run off with Mr Walton. The defendants later admitted disposing of her body but denied Miss Lionnet's murder, blaming each other for her death.

An Old Bailey jury found both of them guilty of the murder following a two-month trial that was described as stranger than fiction.

Miss Lionnet's parents travelled from France to see the disturbing evidence as it unfolded.

The court heard how fashion designer Kouider was fixated with her ex-boyfriend Mr Walton.

After splitting up after two years, Kouider reported him to police more than 30 times and received a caution for falsely branding him a paedophile on a fake Facebook profile.

She also accused him of sexually abusing a cat, using black magic and hiring a helicopter to spy on her.

Giving evidence, Los Angeles-based Mr Walton said he had been "in love" with Kouider but she would "flip" and go "crazy" for no reason.

Another ex-boyfriend Anthony Francois described her as a "lunatic, fickle and unstable".

The mother-of-two created a fantasy world casting Mr Walton as an evil villain who seduced Miss Lionnet with sex and promises of Hollywood stardom.

Banker Medouni became an ardent believer in Kouider's twisted reality and they interrogated Miss Lionnet for hours to get to "the truth".

Jurors heard more than eight hours of recordings in which Miss Lionnet was slapped, likened to a Nazi collaborator and called "worse than a murderer" by her tormentors.

Kouider, who claimed to know influential people including US President Donald Trump, threatened to have her locked up and even marched her to a police station.

The victim's distraught mother Catherine Devallonne had begged Kouider to send her daughter home but she refused.

In her final days, Miss Lionnet was hit with an electrical cable and beaten so badly she had five broken ribs and a cracked breast bone.

In a filmed "confession", the emaciated and broken young woman admitted she had drugged Medouni so Mr Walton could sexually assault him. Within hours, she was dead.

According to Kouider, Medouni tortured her in the bath, then demanded they have sex as her dead body lay nearby.

She told jurors: "He was putting her head under the water and sometimes he would put water on the towel in her mouth. It was getting really mad."

Before the trial, Medouni claimed Miss Lionnet died by accident after he punched her during an interrogation in the bath.

He offered to admit manslaughter but later retracted his confession, saying he made it to protect his wife, who has been diagnosed with a borderline personality disorder.

In his evidence, Medouni claimed his wife had woken him up in a state saying "what have I done, what have I done".

He was shocked to find Miss Lionnet unconscious in the bath and tried to revive her, he claimed.

He said Kouider refused to call 999 and told him they would "burn her" instead.

A witness in the house, who cannot be identified for legal reasons, placed both defendants in the bathroom with Miss Lionnet on the night of her death.

He described hearing Miss Lionnet screaming and splashing in the bath as they said to "breathe".

Prosecutor Richard Horwell QC told jurors that neither were prepared to admit the truth - that they killed her out of "revenge and punishment".

He said their "unhealthy, myopic, all-consuming and groundless" obsession with Mr Walton had deprived them of reason and turned their nanny into "something less than human".

The judge is expected to sentence the pair on June 26 at the Old Bailey.

Miss Lionnet's mother Mrs Devallonne described her daughter's killers as "monsters".

She said: "These self-obsessed individuals who murdered Sophie did not believe Sophie had a value.

"These monsters repeatedly beat Sophie. 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."

The victim's father Patrick Lionnet said: "Sabrina and Ouissem have not only stolen the life of my daughter so brutally and without remorse, they have also stolen mine."

He said what the couple did to his shy and reserved daughter was "beyond comprehension" and "unforgivable".

Aisling Hosein, a Senior Crown Prosecutor from the CPS London homicide team, 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.

“We thank the witnesses in the case along with our colleagues in France for their assistance which has led to these convictions. Our thoughts are with Sophie’s family at this time.”

Folie a deux - madness of two

The murder of Sophie Lionnet bears all the hallmarks of a psychosis known as folie a deux.

Folie a deux, or "madness of two", is defined as a delusion shared from one individual to another.

Depressive and borderline personality Sabrina Kouider was the driving force and weak Ouissem Medouni the willing party.

Even as the true facts were laid bare in court, the pair refused to accept what they had done was the product of their warped fantasy.

Judge Nicholas Hilliard QC said that even though there was evidence about their mental state, in particular Kouider, who was held at a medium secure mental hospital, none of it was a defence for murder.

Other high-profile and extreme examples of folie a deux include serial killers Fred and Rosemary West.

The case of New Zealand teenagers Pauline Parker and Juliet Hulme was made into the film Heavenly Creatures, starring Kate Winslett.

Perhaps the most strikingly similar case to be heard at the Old Bailey involved lesbian child killers Polly Chowdhury and Kiki Muddar in 2015.

The pair were convicted of the manslaughter of Chowdhury's eight-year-old daughter, Ayesha Ali, who died at their home in Chadwell Heath, east London, in August 2013.

Muddar, who like Kouider has a borderline personality disorder, convinced Chowdury her daughter was evil and together they punished and terrorised her with scary masks before she died in the bath.

Unlike Kouider and Medouni, Chowdhury accepted in the trial that she had been swept up Muddar's fantasy world of alter-egos.

Sabrina Koudier

Beautiful but deadly, Sabrina Kouider was the ultimate femme fatale.

The petite Frenchwoman was the star of her own fantasy film noir - and she cast Sophie Lionnet as the enemy.

The glamorous mother-of-two was born in Algeria but grew up with her mother in Paris, where she met her first love in the unlikely form of Ouissem Medouni.

At the age of 18, she had a summer job on a sweet stall at a funfair where she caught the eye of fellow French Algerian Medouni, who was five years her senior.

His ardent pursuit paid off, setting them up for a 17-year on-off relationship which ended acrimoniously in the dock of the Old Bailey.

In common with her other liaisons with men, it was dysfunctional, turbulent and unconventional, and marred by Kouider's bouts of irrational jealousy and violence.

Prosecutor Richard Horwell QC tried to unravel their strange bond, suggesting it was a marriage of convenience which suited Kouider only until someone better came along.

Medouni was said to be weak and easily led, a perfect foil for Kouider's domineering personality.

They both appeared keen to keep their relationship ambiguous, with Kouider regularly relegating Medouni to a relative or friend in public, rather than her life partner with an Islamic marriage certificate to prove it.

At first, Medouni provided some stability and security amid Kouider's emotional turmoil, which, it was claimed, led to more than one failed suicide attempt.

When Kouider went to London to work as a nanny, Medouni followed.

She had turned her hand to pyramid selling for a telecommunications company when Mark Walton, of Boyzone fame, came into the picture.

In 2011, they had a chance meeting in a bank in Notting Hill and he fell head over heels in love.

Once the "love goggles" wore off, Mr Walton discovered a calculating and manipulative woman who could flip and go "crazy" in a moment.

Kouider claimed to know many celebrities and influential people from the party scene, and had been introduced to Blue pop star Duncan James through Mr Walton.

When she split from the music mogul, she went back to Medouni, who would come and go from their Wimbledon flat at will.

She helped with his French pancake stall and, at the time of her arrest, was hoping to get a fashion business off the ground with a show in central London hosted by a major charity.

Despite her grand plans, Kouider kept afloat by claiming benefits and accepting significant financial support from Mr Walton long after they split up.

When the handouts dried up, she racked up £20,000 in unpaid rent on her two-bedroom garden flat in the upmarket area in south-west London.

At the heart of her problems lay depression and a borderline personality disorder, creating a distorted view of the world, her trial heard.

Another ex-boyfriend, Anthony Francois, described her as "fickle" and a "lunatic" who would lie, manipulate and target the weak.

He said she could lash out at complete strangers, grabbing women's hair just for looking at her.

Her character flaws fuelled an irrational obsession with Mr Walton entirely based on an alternative truth created in her mind.

She was so convinced that her ex-boyfriend was colluding with her nanny that she swept Medouni up into the fantasy too.

Frustrated and thwarted in her attempts to get to LA-based Mr Walton, she latched on to her naive young nanny as a soft target.

She was the driving force of the violent interrogations of Miss Lionnet, but claimed Medouni was responsible for her death in September last year.

Oiussem Medouni

Banker Oiussem Medouni "punched above his weight" when it came to the love of his life, according to the prosecution.

The balding 40-year-old French Algerian, known as Sam, was weak, submissive and insular compared with his domineering wife Sabrina Kouider.

When she went off with other men, he proved his unswerving loyalty and waited in the wings for her return, the court heard.

As a young man, Medouni, from Paris, had pursued Kouider relentlessly after seeing her at a French fun fair when she was 18.

He got a degree in economics and went to work for French bank Societe Generale in London as a financial analyst.

Kouider resented him working at weekends and he was made redundant in 2012.

While working, he had invested in two flats in Paris, and survived on the rent while looking to branch out with his own business.

In 2016, he tried to set up a French pancake stall in Wimbledon, but after a trial period elapsed, he failed to produce the funds to hire permanent premises.

Kouider accused him of being lazy, not supporting the family and flitting off to France whenever he felt like it.

But Medouni insisted he did contribute towards the household bills and up-keep.

He showed no signs of mental health problems yet became a fully fledged "believer" in Kouider's obsession with Mark Walton.

Having bought into the fantasy, he took it to new lows, likening Sophie Lionnet to a Nazi collaborator and quizzing her on her sex life.

When Kouider turned violent towards the nanny, he simply went for a walk in the park to get away.

It was suggested that flat-cap wearing Medouni, who was said to be a black belt in Taekwondo, was not as meek as he appeared in the witness box.

Local mother Sadie Nathanson Regan told jurors: "He was not aggressive towards me but he is quite a bit bigger than me. I found him forceful and I found that quite intimidating."

On the day of the au pair's death, Medouni was heard in recorded interrogations to have assumed control for the first time.

He became enraged at the belief Miss Lionnet had colluded to drug him so that Mr Walton could molest him in his own home.

Kouider's defence claimed he was at heart a self-centred man who tortured the au pair to death because the allegations affected him personally.

And after the killing, Kouider alleged that he insisted on having sex with her one last time.

Whether or not Medouni was responsible for killing Miss Lionnet, he admitted that he failed to protect her from his volatile partner.

And in the face of all the evidence to the contrary, he still refused to accept that the obsession with Mr Walton was built on a fantasy.

Mark Walton

Irish-born music mogul Mark Walton suffered the indignity of being wrongly accused of a host of heinous crimes.

Sabrina Kouider branded him a cat abuser, paedophile, and accidental killer of her unborn child, the Old Bailey heard.

She even claimed he had hired a helicopter to hover above her south-west London flat to spy on her.

What tipped Kouider and her partner over the edge was the outrageous allegation that he had conspired with their nanny, Sophie Lionnet, to drug and molest the family.

Softly spoken Mr Walton, 40, shouldered the ludicrous slurs and responded with "integrity and honesty", prosecutor Richard Horwell QC said.

Because he lives in Los Angeles, Mr Walton could not be compelled to give evidence but willingly agreed to bare his soul in front of a packed Old Bailey courtroom.

Dublin-born Mr Walton launched his successful music career in 1993 when he founded Boyzone with a group of friends.

He was with the boyband for a year before he set up Fifth Avenue and has more recently found TV stardom in Asia as a judge on Vietnam's Pop Idol.

The millionaire songwriter, who has worked with the likes of Jennifer Lopez, Shaggy and Enrique Iglesias, described his relationship with Kouider as the most turbulent of his life.

He met Kouider in 2011 at a bank in Notting Hill and it was love at first sight.

Mr Walton, who described himself as a friendly kind of guy, told jurors: "I was in love. She was my life then so..."

They lived together for two years in Queensway, London, before she disappeared without warning.

During their relationship, Kouider would "flip" and became jealous if he spoke to her nannies, he said.

Mr Walton said: "Sabrina shared some stories from her past. I guess knowing that I felt it brought us closer together at times but it was turbulent, probably the most turbulent relationship I had ever been in.

"She would go from softly spoken French accent then she would flip, get very angry, very loud and just not care where we were. She would just go crazy over something trivial."

In 2013, he paid £12,800 in rent on Kouider's Wimbledon flat but stopped the financial support in February 2014, the court heard.

In retaliation, she rang his mother in Dublin, contacted his business partners and created a fake Facebook page on which she called him a paedophile.

He dismissed Kouider's claims against him, saying he had never heard of or met Miss Lionnet and had not been in the UK since October 2015.

In his closing speech, Mr Horwell told jurors: "Walton is a wealthy man - and good luck to him for that - but it is of course a truth universally acknowledged that a single man in possession of a good fortune will often be parted from it."

It was perhaps his generosity towards Kouider that proved his undoing, as the vicious vendetta against him took off after the handouts stopped.