The Quebec Court of Appeal in 2011 ordered a new trial in the case, saying the judge should have allowed Suganthini Mayuran to present a defence of provocation.
Mayuran immigrated to Canada from Sri Lanka in 2004 after an arranged marriage earlier that year.
She moved into an apartment in Montreal with her husband, his father, his mother, his younger sister, his brother Manchutan and Manchutan’s wife Dayani.
In December 2004, Dayani was found stabbed to death and Mayuran was arrested.
It was later alleged the sister-in-law ridiculed Mayuran over her learning ability and a majority of the appeal court judges ordered a new trial, saying that should have gone to a jury.
In a 7-0 decision, the Supreme Court overturned the appeal court and restored the conviction.
In writing for the majority, Justice Rosalie Abella said a defence of provocation requires more than a scolding over someone's learning ability.
She wrote that such a defence requires a wrongful act or insult that must be sufficient to deprive an ordinary person of the power of self-control.
The justice said there was no air of reality to the accused's claim of provocation.
"In order for the defence of provocation to have an air of reality in this case, the evidence must be capable of giving rise to a reasonable doubt that an ordinary person in Suganthini’s circumstances would be deprived of the power of self-control when hearing insults about his or her level of education," Abella continued.
"In my respectful opinion, that conclusion is simply untenable."