The family of a teen fatally beaten with a baseball bat three years ago is frustrated by the sentencing process for the victim's young killer.

Karim Meskine was brutally attacked at a SkyTrain station in New Westminster in December 2013, and spent the following days – including his 19th birthday – in a coma in hospital. He then succumbed to his injuries.

Police said his attack was random, and the 16-year-old killer's intent was to steal Meskine's cellphone.

The teenage killer, who cannot be named because of his age, was found guilty of second-degree murder in June 2016, and the Crown is arguing that he should be sentenced as an adult. The defence wants him to be sentenced under the youth system, meaning he could only serve four years behind bars.

The Crown and defence began legal arguments Monday, and the court heard arguments for both sides that included what kinds of supports and programs may be available. In the federal correctional system, he would have access to job training and therapy.

Meskine's family said hearing the testimony has been incredibly difficult for them. His mother said she's not sure if she can handle a full week of the arguments.

"How long is he going to be in jail for? That's all we want to know," Julie L'Heureux told CTV News.

She previously submitted a letter to the judge calling for the maximum allowable sentence, saying she doesn't care if he's unhappy. 

The Crown said Meskine's killer has been involved in six violent incidents while in custody, including last month when he allegedly punched another inmate in the head.

Arguments and witness testimony are expected to continue over the next few days.

With a report from CTV Vancouver's Maria Weisgarber