The Ontario judge who brought sweeping changes to safeguard drinking water in Canada following the Walkerton water tragedy and who probed the rendition and torture of Syrian-Canadian Maher Arar is stepping down.

"I thank everybody for such a wonderful 14½ years," Justice Dennis O’Connor told a courtroom packed with family and well-wishers at his final sitting today as a judge. "I have always been proud to be able to say that I was a member of the Court of Appeal for Ontario. And I always will be proud to be able to say that looking back."

O’Connor began his law career law in 1966, becoming a judge in 1973 in Yukon, Northwest Territories and northern British Columbia before returning to Ontario to teach, to practise law and eventually be appointed to Ontario’s Court of Appeal in 1998.

Legacy from work on tainted water

In 2000, he was appointed commissioner of the Walkerton inquiry, which concluded failures by the town’s water manager and provincial cutbacks contributed to a deadly outbreak of E.coli contamination in the town water supply that killed seven and made 2,300 sick.

"Justice O’Connor restored dignity to our town," said Bruce Davidson who represented Concerned Walkerton Citizens at the inquiry, and to this day is involved in promoting vigilance for drinking-water safety across Canada.

"When Walkerton and the community questioned the very future viability of the town itself," Davidson told CBC News, "Justice Dennis O’Connor … embraced our wounded community with unparalleled compassion, wisdom and integrity. Listening to the victims, [O’Connor] restored the dignity of the community and launched Walkerton’s journey from water infamy to its current role as a beacon of water excellence.

"Justice O’Connor pledged to and succeeded in leaving no stone unturned to discover the causes of Walkerton’s water disaster and develop recommendations designed to prevent recurrence."

Led Maher Arar inquiry

Ottawa later appointed O’Connor to lead the inquiry into the information sharing by the RCMP and CSIS that led to the U.S. rendition of Syrian-Canadian Maher Arar to Syria, where he was tortured and held for a year, falsely accused of being a member of al-Qaeda.

The inquiry recommended an overhaul and better oversight for the RCMP and Canada’s spy agencies. Arar himself received an apology in January 2007 from Prime Minister Stephen Harper as well as $10.5 million in compensation.

"Justice Dennis O'Connor has been instrumental in helping the public understand what went wrong with our government system, and most importantly, he made important recommendations with respect to how to avoid future tragedies," Arar told CBC News Friday.

"I have found him to be fair, thorough and a man of an immense integrity. The Canadian public will be indebted to him, forever."

Lawyer Paul Cavaluzzo, who worked directly for O’Connor as commission counsel on both the Walkerton and Arar inquiries, echoed those sentiments speaking at today’s "swearing out" session in Toronto.

"Because of his integrity, compassion and empathy he has had this tremendous ability to gain the confidence of — and instil hope — in vulnerable groups of Canadians who have been marginalized either by government, circumstance or indeed history," Cavaluzzo said.

O’Connor is stepping down as a judge, but intends to continue to practise law.