The investigation began in November 2001, after schoolteachers and social workers noticed unusual sexual behavior in four children of the Delay-Badaoui family in Outreau, a town in the Pas-de-Calais region next to Boulogne-sur-Mer, France. Psychologists judged the children's accounts credible. More than fifty people were investigated, and seventeen adults — mostly parents — were prosecuted for child sexual abuse and incest. Their children were separated from them for much of the case, and the accused spent one to three years in pre-trial detention.
Two of the accused drew particular national attention. François Mourmand, accused of murdering a child, died after seventeen months in pre-trial detention, before his case was tried. Daniel Legrand, described as the youngest of the accused, told a judge and the broadcaster France 3 that he had witnessed the murder of a young girl; the child's body was never found.
The first trial opened in May 2004 before the Cour d'assises in Saint-Omer, with three professional judges and nine jurors. The case rested chiefly on Myriam Badaoui's testimony, statements from some of the children — heard behind closed doors, standard practice in France for minors in sexual-abuse cases — and psychiatric evidence. Twelve children were recognised at trial as victims of rape, sexual assault, corruption of minors, and pimping. Of the seventeen defendants, ten were convicted, including four who had confessed, and seven were acquitted.
Six of the ten convicted defendants denied the charges and appealed. At the Paris appeal trial, Badaoui testified on 18 November 2005 that the six "had not done anything" and that she had lied; her former husband, Thierry Delay, corroborated her statement, and two children who had implicated defendants said they, too, had lied. The prosecutor asked the court to acquit all remaining defendants, and on 1 December 2005 all six were acquitted, ending the trials. Paris's general prosecutor, Yves Bot, apologised to the defendants on the trial's final day, before the verdict was delivered.
Four convictions became final because those defendants had not appealed: Thierry Delay, sentenced to twenty years; Myriam Badaoui, sentenced to fifteen years and released in 2015; and a neighbouring couple. Delay, Badaoui, and one of the neighbours later acknowledged wrongly accusing other people, when only the four of them had taken part. President Jacques Chirac and other officials apologised to the acquitted, who were compensated for their detention. A parliamentary inquiry opened in January 2006, broadcast live on television, to examine the roles of expert witnesses, the investigating magistrate, and media coverage. In 2009, France's judicial oversight body reprimanded the investigating magistrate, Fabrice Burgaud — the lowest disciplinary sanction available; he again denied wrongdoing at a further hearing in 2015.
The case's legacy remains contested. In 2007, Le Point revealed a confidential government report finding signs suggestive of sexual abuse in five children whose parents had been acquitted; the report was never published or independently proven. Two of the acquitted, Franck and Sandrine Lavier, were convicted in 2012 of habitual non-sexual violence against two of their children, and in 2023 Franck Lavier was separately sentenced to six months in prison for sexually assaulting his daughter. Saint-Omer's prosecutor at the time, Éric Maurel, later told a judicial inquiry that child witnesses had been harassed by defense questioning. One of the Delay-Badaoui children, Jonathan Delay, publicly objected to a 2023 television dramatization of the case. Convictions for child sexual assault in France fell 40 percent in the decade following the 2005 acquittals.