A mistrial will be declared for Jonathan Mahautiere, accused of killing his ex-girlfriend Gabrielle Dufresne-Elie.
Mahautiere was arrested in June 2014 immediately after the attack and charged with second-degree murder.
His trial began earlier this year, and last week was sent to the jury.
Members had the choice of convicting him of second-degree murder or the lesser charge of manslaughter but after eight days, the jury said it is unable to come to a unanimous verdict.
Testifying in court, Mahautiere, who is now 21, admitted that he was very upset about their breakup and strangled the girl in a hotel, so the jury was not allowed to find him not guilty.
"I think the jury has done everything it can. It's been a very long week for them," said Crown prosecutor Genevieve Dagenais.
Dufresne-Elie was 17-years-old and about to graduate from Marguerite De Lajemmerais high school.
A new trial may take place later this year unless the Crown and the defence lawyer can work out an agreement.
Defence lawyer Clemente Monterosso said his client was worried about what was yet to come.
"He was stressed, evidently. He's a young man who just turned 21, and he was 18 when this act occurred," said Monterosso.
