Agnès Marin was born to Paola and Frederic Marin. According to a close friend, she was a good student who was interested in becoming a filmmaker. Her parents had enrolled her at the Cévenolles boarding school in 4th grade after being exposed to negative influences including marijuana at her former junior high school. She was buried on her would-be 14th birthday, November 26, 2011.
On November 11, 2011, in Chambon-sur-Lignon, in the département of Haute-Loire, Agnès Marin, a 13-year-old student at Les Cévenoles Boarding School, went with Mathieu Moulinas, another student, who was nearly 18 at the time, to look for hallucinogenic mushrooms in a forest. Once there, Moulinas proceeded to rape and stab Agnès 17 times before finally burning her body with petrol that he had brought to the site previously.
At his trial before the Cour d'assises des mineurs that began on June 18, 2013 and was held in camera for the most part at the request of Salomé F. in spite of the Marins' wishes and during which Mathieu recognized his guilt, the prosecutor criticized the numerous failings of the institutions and asked the jury to not grant the benefit of minority to Moulinas, instead asking for a 30-year sentence and civil commitment, taking into account the fact Moulinas had mental problems.
On June 28, 2013, Moulinas was sentenced to life imprisonment, a sentence which had not been met against a juvenile since Patrick Dils in 1989 (who was subsequently exonerated in 2002.). His lawyers appealed the sentence the next day.
The murder was committed during a time when the French public was debating juvenile criminality and recidivism among offenders.