A former French anaesthetist has gone on trial accused of deliberately poisoning 30 patients, 12 of whom died.

Frédéric Péchier, aged 53, is alleged to have tampered with intravenous medicines at two clinics in the eastern city of Besançon between 2008 and 2017.

Prosecutors say he caused cardiac arrests as a way of seeking revenge against colleagues, making him the “common denominator” in the unexplained medical emergencies.

The case first came to light in 2017 when an otherwise healthy 36-year-old woman suffered a cardiac arrest after spinal surgery. Tests later revealed abnormal concentrations of potassium in her treatment, raising suspicions of poisoning. Investigators eventually linked Péchier to dozens of adverse events over nearly a decade, including fatal cases involving patients as young as four and as old as 89.

Despite the charges, Péchier has remained free under judicial supervision and denies all wrongdoing, insisting there is “no proof of any poisoning.”