MONCTON, N.B. -- Justin Bourque's killing of three Mounties has been described in court as one of the worst crimes in Canadian history, prompting recommendations from Crown and defence lawyers for the harshest sentence in more than 50 years.

Judge David Smith, chief justice of the Court of Queen's Bench in New Brunswick, is scheduled to sentence the 24-year-old Friday, four months after Bourque used a semi-automatic rifle to fatally shoot three officers and wound two others in Moncton's north end.

Bourque pleaded guilty in August to three counts of first-degree murder and two counts of attempted murder.

The Crown is seeking the maximum sentence -- 75 years without eligibility to apply for parole -- under a section of the Criminal Code that was amended in 2011.

Prior to that, Bourque would have been handed an automatic life sentence with no chance at parole for 25 years, the mandatory penalty for one or more convictions of first-degree murder.

However, the amended legislation gives the judge the option of extending Bourque's parole ineligibility because he is a multiple murderer. The legislation is called the Protecting Canadians by Ending Sentence Discounts for Multiple Murders Act.

Smith could decide that the 25-year ineligibility period for each of the three murder convictions should be imposed consecutively for a total of 75 years, which means Bourque wouldn't be allowed to apply for parole until he was 99 years old.

Earlier this week, defence lawyer David Lutz said his client, having admitted to the crimes in a detailed, three-hour statement to police, has argued that a 50-year parole ineligibility period would be fair. Lutz had little else to say on his client's behalf, except that Bourque has a defective thought process and inadequate social skills.

If Smith accepts either the Crown or defence recommendations, the sentence would be the harshest since Canada's last executions in 1962.

In September 2013, a judge in Edmonton sentenced an armoured-car guard to life in prison with no chance at parole for 40 years for shooting four of his colleagues during a robbery in June 2012.

Travis Baumgartner had pleaded guilty to one count of first-degree murder, two counts of second-degree murder and a charge of attempted murder.

The judge in Bourque's case is not bound by the recommendations from the Crown and defence, said Carissima Mathen, a law professor at the University of Ottawa.

However, Mathen said the judge doesn't have much room to move, given that the penalty for first-degree murder is fixed at 25 years. It would appear the judge's only choices are 25, 50 or 75 years of parole ineligibility.

"The only flexibility the judge has is if he were to conclude that imposing that level of parole ineligibility would violate Justin Bourque's rights under the Charter of Rights," Mathen said, adding there could be an argument that a 50- or 75-year sentence could be seen as cruel and unusual punishment.

"There's been a belief for many years that very long sentences don't necessarily serve social interests. ... The federal government clearly views that as being soft on crime and perhaps not fully recognizing the gravity of multiple convictions for offences that are similar."

Mathen said the Conservative government has been consistent in making criminal law more punitive to express greater denunciation of horrendous crimes and reflect greater respect for victims.

The problem, she said, is that rehabilitation is at the heart of the parole and correctional systems.

"It's not solely about denouncing the crime," she said.

"If someone is not ever going to re-enter society because their sentence is so long, then I think it's fair to ask: Is there any point in offering programs within prisons to develop skills ... and deal with emotional and mental trauma? If not, that will lead to conditions in prisons that are probably inhumane."

Law professor Archie Kaiser said the judge cannot be influenced by the public mood, despite the horrific nature of the crimes.

Kaiser also said he was surprised by the approach taken by Bourque's lawyer.

"I don't mean to second-guess anyone in the circumstances, but I might have expected a constitutional challenge to the amendment or the submission of expert reports on the mental state of the accused," said Kaiser, who teaches at Dalhousie University in Halifax.

"I think that both might have assisted the court in appreciating both the gravity of the changes in the legislation and also the kinds of factors that might help mitigate his sentence."

Bourque has undergone a psychiatric assessment, but its contents have been sealed by the court.