There were cheers in a Sydney, N.S. courtroom today as a Cape Breton teen was found guilty of second-degree murder in the gruesome stabbing death of his girlfriend.

The judge called the case a “wrenching tragedy” and her decision caused the teen to lash out at the girl’s family, who cried tears of joy as the guilty verdict was read.

The victim and the teen had dated for about three months before the attack, which took place at the former home of his grandfather in Whitney Pier.

The defence had asked that the charge against the teen be reduced to manslaughter, arguing he had acted in an intoxicated fit of rage after hearing his girlfriend had cheated on him.

But Judge Anne Derrick ruled there was plenty of evidence to suggest the teen knew exactly what he was doing when he stabbed her 104 times in December 2010.

One example she used was that after a knife blade broke off inside the victim, the teen found another knife and continued the attack against her.  

Derrick said she believed the teen didn’t remember the stabbing because he was intoxicated with drugs and alcohol at the time of the attack, but also said that doesn’t mean the intent to kill his girlfriend wasn’t there, as argued by the Crown.

“From the very beginning we gave notice that this should be a second-degree murder charge,” said Crown attorney Dan MacRury. “We’re very pleased that the judge agreed with our arguments in relation to that, and from the beginning, we believed that it should be an adult sentence. Obviously that’s the next stage of the proceedings.”

The 18-year-old was 16 at the time of the murder and was tried under the provisions of the Youth Criminal Justice Act which prohibits the publication of his name and that of the victim, a 17-year-old girl from Glace Bay.

The 10-day trial heard testimony from 23 witnesses and included 131 exhibits.

The victim’s family and friends sat through much of the trial, donning T-shirts with a picture of her face and the words ‘remember me.’

Four days have been set aside in November, when the Crown will argue that the teen should be sentenced as an adult.

If the court agrees, the automatic sentence for second-degree murder is life in prison with a possibility of parole after seven years.

If he is sentenced as a youth, the teen is facing a seven-year sentence, with four years spent in custody and three in the community.

With files from CTV Atlantic's Ryan MacDonald