A court has heard how a couple who murdered a young woman and burned her body were afflicted by 'folie a deux' - here's what it means

A court has heard how a couple who murdered a young woman and burned her body were afflicted by 'folie a deux' - here's what it means

  • A London couple have been convicted of killing and burning the body of a woman called Sophie Lionnet.
  • The court heard they had been afflicted with folie À deux, or "madness of two."
  • One of the pair became paranoid that Lionnet had run off with her ex, whom she was obsessed with.
  • It is a rare psychological phenomenon but there have been several cases of shared delusions.
  • Sometimes it can involve more than two people.

On Thursday May 24, a couple were found guilty of murdering their French nanny and burning her body on a bonfire in their London backyard.

After six days of jury deliberation, 35-year-old Sabrina Kouider and 40-year-old Ouissem Medouni were found guilty of killing Sophie Lionnet, a 21-year-old French nanny, after beating, starving, and torturing her over a bizarre paranoid delusions about Mark Walton - Kouider's ex-boyfriend and a founding member of the pop group Boyzone.

The court heard that the couple had been afflicted with a psychosis known as folie À deux, or "madness of two," which is where delusions are shared between people.

Kouider lived in a warped reality, allegedly due to her bipolar disorder and depression, and Medouni was a willing party in it. Kouider was apparently obsessed with her ex-boyfriend, reported him to police over 30 times, and falsely accused him of paedophilia on Facebook.


Other strange accusations included him hiring a helicopter to spy on her, and sexually abusing a cat.

Kouider also reported to the police that Lionnet had run off with Walton, which was the primary reason the couple locked her up. In the final days before she died, Lionnet was subjected to horrific abuse including being hit with an electric cable and being beaten so badly she had five broken ribs and a cracked breast bone.

In court, Kouider and Medouni blamed each other for Lionnet's death, still making accusations against her, which the judge concluded had "no truth whatsoever."

Folie À deux, or Shared Psychotic Disorder, can occasionally involve more people with close bonds known as folie À trois, folie À quatre, or folie en famille (family madness). It was first conceptualised in the 19th century by Charles Lasègue and Jean-Pierre Falret.

It is not listed as a separate disorder in the most recent Diagnostic and Statistical Manual of Mental Disorders, DSM-5, but is included under the schizophrenic spectrum and other psychotic disorders.


The first known case study appears in Enoch and Ball's "Uncommon Psychiatric Syndromes," which involved a woman called Margaret and her husband Michael in the 19th century. Both were 24 years old, and were found to be sharing paranoid delusions about an invader. They believed someone was coming into their house, spreading dust, and wearing down their shoes.

Essentially, Margaret and Michael got themselves into a feedback loop where they reinforced each other's delusions.

Folie À deux is most common between romantic couples, but it can also occur with siblings. For example, in one case involving three sisters, two moved into a house near the third to help her care for her children. Over time they all became closer and more heavily involved with religion.

The youngest sister then started thinking the Bible was full of inconsistencies and became determined to correct them. The sisters ended up praying nonstop for three days without sleeping, then became convinced God wanted them to have a particular house in the town that didn't belong to them.

They went round demanding to be let in, breaking down windows and attacking the owner until they police arrived. They were arrested, and put in the same holding cell where they continued to pray and sing while naked, and occasionally attacked the guards.


In 2016, there was a case of a family of five who disappeared on a road trip. Mark and Jacoba Tromp took their three adult children and fled their home, travelling over 1,600 km in a week across the US state of Victoria. They had been suffering from increasing signs of stress and paranoia, and were convinced someone was going to rob and kill them.

One of the sons, Mitchell, was apparently the only one not succumbing to the psychosis. He was the only one to keep ahold of his phone, but as his parents became more delusional, they made him throw it out the window because they thought they were being tracked.

In the case of the sisters, all they needed was separation. Once they had some time away from each other, their psychosis vanished without any need for medication. But in some cases, like that of Kouider and Medouni, delusion can be more heavily imposed by one partner.

According to The Telegraph, Kouider was "the star of her own fantasy film noir - and she cast Sophie Lionnet as the enemy." She was described by ex-partners as manipulative, fickle, and a "lunatic," while Medouni was "weak" and "easily led."

In cases where separation isn't enough, doctors usually treat extreme cases of psychosis with anti-psychotic medications. It is unclear whether Kouider is being given treatment, but she was being held at a medium secure mental hospital before the trial.