On the evening of June 1st, 1999, in the quiet Burgundian city of Mâcon, France, seventeen-year-old Vanessa Thiellon left her family home on boulevard Henri-Dunant after a heated argument. Vanessa, an apprentice chef who was described as lively and determined, reportedly left to meet her boyfriend, known in reports as Seyit, following the dispute that played out partly over the phone.
She never returned home. Her family reported her missing almost immediately. The teenager simply vanished from the streets of Mâcon.
Four days later, on June 5th, 1999, a grim discovery ended the desperate search. Vanessa’s body was found on the banks of the Saône River in central Mâcon, not far from the A6 motorway corridor. She was discovered nude and showed visible signs of severe violence: her body was covered in bruises, indicating she had been badly beaten.
The location along the Saône in Mâcon placed the case geographically close to several other unsolved disappearances and suspicious deaths of young women along the A6 motorway axis in the region during the 1980s–2000s (a series sometimes referred to as the A6 disappearances). However, investigators ultimately treated Vanessa’s death as a distinct case rather than definitively linking it to a serial pattern.
The initial autopsy proved inconclusive on the exact cause of death. No evidence of sexual assault was found, which set the case apart from several other regional crimes. Bruises and signs of beating were clear, yet the medical examiner could not establish a definitive mechanism of death.
Early speculation included overdose (though toxicology results did not confirm this), accidental drowning, suicide (though no supporting evidence emerged), or homicide. The absence of a clear cause of death created lasting uncertainty and hampered the investigation from the beginning. Eventually, the case was classified in the direction of homicide involontaire (involuntary manslaughter / unintentional killing), a qualification that has remained.
Almost immediately, attention focused on Vanessa’s boyfriend, Seyit. In January 2000, he was placed under formal investigation for involuntary manslaughter. Notably, he was not remanded in custody.
More than a quarter century later, that status has not fundamentally changed: no trial has taken place, no conviction has been secured, and the case has never been officially closed or definitively solved.
The case saw periodic revivals, such as in 2010, when forensic advances prompted a brief relaunch. Further, in 2016, authorities decided to exhume Vanessa’s body in hopes that modern techniques (toxicology, DNA, etc.) could reveal new evidence. The exhumation was carried out that year, but no public breakthrough followed.
In 2023, nearly twenty-four years after the events, the dossier was transferred to the national pôle cold cases unit in Nanterre, created to handle long-unsolved violent crimes with renewed resources, specialized investigators, and advanced forensic capabilities.
As of 2026, the file sits with France’s cold-case specialists. Whether new forensic methods, re-interviews, or re-examination of existing evidence will finally provide answers for Vanessa’s family remains unknown.
Crime Immemorial 