Three people convicted of killing a woman have lost their bid to appeal their conviction.

Gabrielle Frechette, Ginette Duclos, and Gerald Fontaine were sentenced in January 2016 to three years and two years in prison for criminal negligence causing the death of Chantal Lavigne.

In 2011 the three culprits had wrapped Lavigne in mud, a plastic sheet, and placed a cardboard box over her head for nine hours as part of a spa treatment.

A coroner said that Lavigne was cooked alive.

Frechette had organized the "treatment" as part of a personal growth seminar that made several people very ill.