In her judgment delivered Monday, Judge Hélène Fabi said she did not believe the defendants’ defence and that the sweating experience made for extremely dangerous conditions.
Lavigne died after undergoing a detoxification process that involved intense sweating at a farmhouse in Durham, a small town near Drummondville.
The detox therapy session was part of a seminar called "Dying in Consciousness," led by a self-styled Quebec therapist.
The three on trial were also found guilty of criminal negligence causing bodily harm for a second woman, Julie Théberge, who recovered.
Wrapped in plastic, encased in cardboard
Lavigne and another woman were rendered unconscious by the excess sweating and were transported to hospital.
"The treatments consisted of a process of sweating by being all wrapped in plastic with mud, and also with blankets," said Sgt. Éloise Cossette of Quebec provincial police at the time. Both women were also encased in cardboard boxes.
Lavigne, a 35-year-old mother of two, died hours later of hyperthermia — a medical emergency caused by failed thermoregulation, when the body produces or absorbs more heat than it can dissipate. Lavigne’s coroner’s report said she literally cooked to death.
Her body temperature at the time paramedics found her was at 40.5 C. Normal human body temperature is 37 C.