Two Supreme Court of Canada judges have announced they will step down at the end of August, giving Prime Minister Stephen Harper an immediate opening to shape the court.

Justice Ian Binnie, 72, and Justice Louise Charron, 60, have written to Federal Justice Minister Robert Nicholson, to inform him of their plans, both effective Aug. 30, Chief Justice Beverley McLachlin said Friday in a release. Binnie has indicated a willingness to stay longer if needed during the judge-selection process.

Four of the court's nine judges were expected to retire by 2015, including Binnie. But Charron is a surprise.

Including Justices Marshall Rothstein and Thomas Cromwell, appointed in 2006 and 2008, it means Harper will have appointed more than half the court by the end of the current majority government's term.

Emmett Macfarlane, a Canadian visiting researcher at Harvard law school whose work looks at how the court makes decisions, says Harper has the chance to shape the court by appointing people who lean toward a conservative approach, but he cautions against concluding that's what will happen.

Macfarlane says Canada doesn't tend to have judges as conservative as Americans like Antonin Scalia or Clarence Thomas.

"I wouldn't overstate the extent to which ideological leanings are going to matter," Macfarlane said. "But these appointments can make a big difference. Who you appoint matters on the court. The issues they decide are heavily political, social and moral issues often, especially when dealing with cases pertaining to the Charter of Rights."

Ontario bench 'deep'

At least one vacancy is expected to be filled from Ontario, and "the Ontario Court of Appeals bench is very deep," Macfarlane said.

Appeal court judges Gloria Epstein, Robert Sharpe and Marc Rosenberg are considered strong candidates, as well as lawyer Guy Pratte.

Macfarlane says he's watching to see whether Harper has the next justices questioned by a House of Commons committee, a process he used in 2006 but skipped in 2008 as he tried to get Cromwell in place before the court's fall session started.

He says he likes that method because it gives Canadians a look at who sits on the court and how they're chosen.

"Not a lot of Canadians are all that aware of who the individuals are who actually sit on the Supreme Court," he said. "And that type of a process ... allows us to know a little bit about the thought process of these appointees who will potentially go onto make extremely important decisions."

Rod Snow, president of the Canadian Bar Association, which is traditionally consulted prior to an appointment, says the group wants a transparent process to fill the vacancies. He urged Harper to form an advisory committee including MPs from all parties, as well as judges, lawyers and citizens.

'It has been an honour'

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Justice Louise Charron

"It has been an honour and a privilege to serve on the Supreme Court of Canada since January 1998," Binnie wrote. "Much as I will miss the work and my colleagues, I am now well into my 14th year on the court, and the time has come to return to Toronto to pick up some of the threads of an earlier existence."

Charron said her reasons for retiring are quite simple: she recently turned 60.

"As promised when I took the oath of office, I have brought to this task my best, every day, whatever that could be at the time," she said. "I hope that I have lived up to the trust and honour that was bestowed upon me."

Binnie has been on the Supreme Court since 1998 and was due to retire within the next three years.

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Justice Ian Binnie

Charron joined the bench in 2004, but is stepping down well before the mandatory retirement age of 75.

Charron's resignation is surprising, judicial experts say, because she has only been with the court since 2004 and because she is so young.

McLachlin says she hopes the government makes the selection of new justices a priority and uses the care and deliberation that is required.

Binnie was born in Montreal and graduated in law from the University of Toronto in 1965. He also has two law degrees from Cambridge University. He was a litigator with Wright & McTaggart and its successor firms until 1982, then became an associate deputy minister of justice with the federal government. Binnie was a senior partner at McCarthy Tétrault from 1986 to 1998, when he was appointed to the Supreme Court.

Charron was born in Sturgeon Falls, Ont., and graduated in law from the University of Ottawa in 1975. She practised with the firm Lalonde, Chartrand & Gouin in civil litigation, then began a career as an assistant Crown attorney and district court judge. She was promoted to the Ontario Court of Appeal in 1995, and to the Supreme Court of Canada in 2004.

With files from The Canadian Press