The first judge in a decade to join the Supreme Court of Canada without any parliamentary scrutiny takes his seat Monday, just in time for a fall session featuring important cases on assisted suicide, religion in the public sphere and an Ottawa-Quebec dispute over gun-registry data.

Justice Clément Gascon of Quebec is a commercial law expert with little background in criminal law. No selection panel of parliamentarians put his name on a shortlist. No public hearing was held in Parliament about his appointment. And Prime Minister Stephen Harper did not cite any of his rulings when he named the 54-year-old Montrealer to the court.

Justice Gascon, who has declined to give interviews since his appointment in June, fills a spot that has been empty for a year, the longest vacancy in the court's 139-year history. Mr. Harper had chosen Justice Marc Nadon for that spot last September, but the Supreme Court ruled him ineligible.

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After the Nadon rejection, the federal government chose not to use a panel made up of government MPs and opposition members in winnowing down candidates to a short list of three, or to hold a public hearing in Parliament at which the judge could be questioned.

"One of the byproducts of the Nadon fiasco is 'we're going to blame the process, instead of looking at ways to fix it. We're just going to appoint whoever we want.' There's no sense of the considerations that fed into the government's ultimate pick," University of Ottawa law professor Carissima Mathen said.

Asked about the criticism, Clarissa Lamb, a spokesperson for Justice Minister Peter MacKay, said "these appointments have always been a matter for the executive and continue to be."

Where Justice Nadon was described as a "vocal arch-conservative" by author Rosemary Sexton – whose husband Edgar was a colleague of his on the Federal Court of Appeal – Justice Gascon is more comfortable in applying precedent than in striking out in new directions, a Quebec observer said. "He is not going to be pushed by his own thoughts about what the Constitution should be; he will be trying to decipher what it is, and how to apply it to the detailed facts at hand," lawyer Simon Potter of Montreal says. He describes him as a judge of "absolute intellectual rigour."

In his first two weeks, he will almost certainly be asked to take part in three intensely watched cases. The biggest of the three is a test of when judges should defer to Parliament and when they should make policy. The Criminal Code prohibits helping a person to die by suicide. The question for Justice Gascon and the rest of the court is whether that prohibition is so shockingly unfair to sick people in extreme pain that the government must scrap it.

The other two are Quebec cases. One asks whether the Saguenay municipal council's use of Christian prayer before its meetings and its display of Christian symbols violate a duty of neutrality and the constitutional rights of non-believers. In the other, Quebec will try to persuade the Supreme Court that it should support "co-operative federalism," and not allow the Conservative government to destroy the data from its defunct long-gun registry. Quebec wishes to use the data for its own registry.

And next month, a central feature of Mr. Harper's crime agenda, mandatory minimum jail sentences for illegal gun possession, will be challenged as a form of cruel and unusual punishment.

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Justice Gascon is Mr. Harper's sixth appointee to a nine-member court that has handed the Conservative government a series of stinging defeats, softening its crime laws. He was not on the secret list of six candidates drawn up by the Prime Minister's Office and the Justice Department a year ago, a list obtained by The Globe.

Justice Gascon spent two years on the Quebec Court of Appeal, and 10 years on the Superior Court. He did not sit on the Superior Court division that deals with criminal cases. He wrote a 2009 ruling giving bank customers the right to sue in a class action. A former labour lawyer with Heenan Blaikie in Montreal who worked for the employer side, he ruled against the unions in a major 2003 challenge to federal employment insurance. Had he been vetted by a parliamentary selection panel, he would have had to choose five of his rulings to submit, and the public would have been able to read them after he was chosen.

The son of a doctor, Justice Gascon is a father of three married to a Quebec judge. He could spend two decades on the court; mandatory retirement age is 75. He has led seminars for judges in how to write judgments.

Liberal MP Irwin Cotler, a former justice minister who developed the country's first process for involving Parliament in the selection of Supreme Court judges in 2004, said "secrecy" harms the integrity of the Supreme Court, and is unfair to Parliament, to Quebec and to the judge himself.

"There's nothing here to hide, and everything to be gained by a public, inclusive process," he said in an interview.