Amir Belkacemi stood in a Quebec City courtroom on Wednesday and called Alexandre Bissonnette a ”monster,” urging a judge not to ever let his father’s murderer walk the streets again.

Mr. Bissonnette, who pleaded guilty to six counts of first-degree murder in the Quebec City mosque attack last year, faces the possibility of a sentence unprecedented in Canadian history: 150 years before he is eligible for parole.

That possibility, and other multiple-murder cases in the past five years that would leave convicted killers in prison for their entire lives, has touched off a debate about the law that allows for it.