The trial for a teenage girl charged with first-degree murder in connection to the death of man at a house party last January started in a Calgary courtroom on Monday.

The girl can’t be identified because she was just 17-years old when Brett Wiese was stabbed to death on January 12, 2013 at a home in the 5100 block of Brisebois Dr. N.W.

The teen and her friends were uninvited guests at the party that was also attended by Wiese.

The Crown says that when the teen and her friends were asked to leave, she began fighting with one of the hosts and demanded to know who was kicking her out of the party.

She then allegedly threatened to return with more friends.

The Crown says that the entourage returned two and a half hours later armed with knives.

Two young men were stabbed as a result. 

One man sustained life-altering injuries, including one partially collapsed lung, one fully collapsed lung and a partially damaged aorta.

Brett Wiese was stabbed seven times and was transported to hospital where he died from his injuries.

The Crown says, the teen was the instigator of the attack and that if she is convicted, it will apply to have her sentenced as an adult.

 “It's a very nerve wracking experience. She’s doing as well as she can under the circumstances but we’re all aware of the potentially severe consequences here and it's very serious,” said Defence attorney, Janna Watts.

The teen girl is charged with first-degree murder.

Nearly two dozen friends and family of the victim attended court sporting buttons with Wiese’s photo on it and vow to be in court for as long as it takes to get justice.

Mitchell Harkes, 20, is also charged in connection to Wiese's death.

His trial is scheduled for September and is expected to last a month.

(With files from Elissa Carpenter)