Sorella showed no emotion as the jury delivered its verdict. She faces an automatic life sentence with no possibility of parole for 25 years.
The jury deliberated for four days in what the Crown prosecutor called a difficult case.
They had four verdicts to consider:
- First-degree murder
- Second-degree murder
The sisters were first discovered by their grandmother, who found the bodies lying side by side in the family's Laval home.
The bodies showed no signs of violence and the cause of their deaths remains unknown.
The Crown had suggested the girls could have been killed inside a hyperbaric chamber, which the family had on-hand to treat the youngest daughter's juvenile arthritis.
The defence argued that no traces of clothing fibres were found inside the chamber.