Judge Guy Gagnon was born in Amos, Québec in 1953. He attended college in Rouyn-Noranda and then earned his Licentiate in Laws from the University of Ottawa in 1977. Called to the Québec Bar in 1978, he completed the course requirements for a Master's degree in public law in the same year.
From 1978 to 1992, he practised law in a private firm, where two of his partners at the time were appointed judges: the Honourable Jacques Viens became a Superior Court judge and the Honourable François Godbout, a judge of the Court of Québec.
During those years as a lawyer, Judge Gagnon had the opportunity to specialize in civil and commercial law, in particular. In the course of his law practice, he was called upon to sit on various boards of directors of both public and private companies.
In 1992, he was appointed a judge of the Court of Québec, where he served on the bench, indiscriminately, in the civil division, the criminal and penal division as well as the youth division; moreover, he was a member of the itinerant court, where he worked 11 years in all Far North communities in Québec—in James Bay, Hudson Bay and Ungava Bay. On August 29, 2001, he was appointed coordinating judge of the Court of Québec, for the judicial districts of Abitibi, Rouyn-Noranda and Témiscamingue.
In September 2003, the Québec government appointed the Honourable Guy Gagnon Chief Judge of the Court of Québec, for a 7-year term of office, and he thereby also became Chairman of Québec's judicial council. Responsible for managing the Court, he is moreover the representative and spokesperson in dealing with the Government and with the other courts in Québec, in addition to all the other Canadian judicial bodies in Canada. His responsibilities include ensuring compliance with Court policies on judicial affairs as well as with codes of ethics.
As Chief Judge of the Court of Québec, he has written various articles and given a number of speeches on a variety of topics, including: disqualification (récusation), expert, judicial independence, administrative autonomy of the courts, judges and the media, etc.
On September 3, 2008, the University of Ottawa's Faculty of Law awarded him an Order of Merit. As well as on September 3, 2009, the Bar where he was called during his first years presented him with the "Mérite du Barreau de l'Abitibi-Témiscamingue". On October 18, it is the turn of the "Association des avocats de province" to honor him with the Merit of the Association.
On September 9, 2009, the Honourable Guy Gagnon was appointed a Judge of the Quebec Court of Appeal, with effect as of September 27, 2009.
During a speech on Judges' Day, August 19, 2008, at The Canadian Bar Association's conference, attended by a wide range of members of Canada's judiciary, Judge Gagnon stated:
"Gone are the days when judges could base their legitimacy solely on characteristics inherent in judicial power. Our fellow citizens want to understand the system, evaluate it, and indeed, even judge it as well. I would say that just like all public organizations, the courts are no longer free from this unofficial—but so very real—obligation of being more accountable to the public, in general, and the government, in particular."