Cathie Gauthier is sentenced to life in prison with no possibility of parole for 25 years. She was convicted by a jury on Oct. 24, 2009, for the murders of Joëlle, 12, Marc-Ange, 7 and Louis-Philippe, 4, her children with Marc Laliberté.
They died at their home in Chicoutimi, a suburb of Saguenay, after ingesting a mix of Gravol and a tranquillizer prescribed to Laliberté.
The Crown prosecutor successfully argued at the original trial that Gauthier and Laliberté had a murder-suicide pact that they carried out on New Year's Eve 2008.
Gauthier's husband died after his left wrist was slit, the bleeding worsened by a heart condition.
Her lawyer argued in front of Canada's top court that Gauthier had backed out of the pact at the last minute.
In the days leading up to New Year's Eve, she and her husband wrote letters to friends, family and members of the French-language media explaining that they wanted to die along with their children, and that they would all be dead by the time the letters were read by their intended recipients.
Gaétan Ringuette, a provincial police officer who worked on the case, previously testified he had found some of those letters on the kitchen counter.
The couple had filed for bankruptcy in October 2008 after experiencing months of financial hardship.