The Supreme Court of Canada will not hear the case of a man convicted of murdering his three sisters and another woman.

Hamed Shafia had sought leave to appeal to the court, arguing that new evidence showing he was a youth at the time of the deaths should not have been dismissed.

As is its practice, the Supreme Court did not give reasons for its ruling.

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But Nick Bala, a law professor at Queen's University in Kingston, Ont., said the high court was "clearly not concerned with the approach of the Court of Appeal" in assessing the rare and narrow legal issue raised by Shafia.

"The issue of his age was completely lacking in any credibility," given that Shafia came to Canada with his parents, who would have known when he was born, Bala said.

Though there have been cases involving minors who came to Canada unaccompanied from third-world countries whose age was uncertain, to have it come up after trial in circumstances such as Shafia's is "unprecedented in Canada," he said.

Thursday's ruling means Shafia has exhausted his options to fight his sentence, the professor said.

"This tragic saga is, from a legal perspective, over," he said.

Shafia's lawyer did not immediately respond to a request for comment.

Shafia and his parents were found guilty in January 2012 of four counts of first-degree murder in the deaths of his teenage sisters and his father's first wife in a polygamous marriage.

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The four bodies were found in a car at the bottom of the Rideau Canal in Kingston, Ont., in June 2009.

At trial, the judge described the killings as being motivated by the Shafia family's "twisted concept of honour."

The Ontario Court of Appeal earlier rejected Shafia's argument that he was too young to be tried as an adult and should have been tried separately.

The appeal court found no reason to allow Shafia's new evidence, which it said was not compelling.

The Shafia family was originally from Afghanistan but fled at the outbreak of war in the country and eventually immigrated to Canada.

The new documents regarding Shafia's age were found when his father sought to transfer property in Afghanistan and asked someone in that country to prepare the paperwork, court documents show.

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That person discovered Shafia's original Afghan identity document that recorded his birth date as Dec. 31, 1991, making him a year younger than initially thought, the documents said.

Other records were later obtained from the Afghan government to confirm the date, the court documents said.

But instead of applying the usual test for introducing new evidence — called the Palmer test — the appeal court devised a new test in which Shafia was required to show that the documents were "compelling" evidence of age, his lawyers said at the time.

The appeal court ruled the evidence did not meet that test.

An adult convicted of first-degree murder faces life without parole for 25 years, while a young offender, when sentenced as an adult, faces a maximum of life without parole for 10 years.