Devontay Hackett has been found guilty of second-degree murder in the prom-night killing of 18-year-old Brandon Volpi.
Volpi was stabbed in the neck and chest during an altercation outside Les Suites Hotel in downtown Ottawa during an after-prom party in June of 2014.
Witnesses said Hackett, who was also 18 at the time, was fighting with another student over a missing cellphone when Volpi was asked to intervene.
The jury took two days to reach its verdict.
The mandatory minimum sentence for second-degree murder is life without parole for at least ten years.