Mr. Coo was called to the Bar in both British Columbia and Ontario in 1953, after attending Upper Canada College and obtaining an LL.B. with Honours from the University of Toronto Law School.

His practice in Toronto and throughout Ontario was confined to court work, with emphasis on all aspects of civil litigation. He was appointed Queen's Counsel in 1964.

Mr. Coo was appointed a judge of the County Court in Toronto in 1973, Senior Judge of the District Court in 1979 and a judge of what is now the Ontario Superior Court in 1990. He had experience as a judge in all phases of the litigation process and was experienced for over 32 years in all matters which come before the court.

In the mid-1970's, before he became the Senior Judge in Toronto and after he attained that office, Mr. Coo introduced into the court system under his direction the concept of settlement conferences, applicable to all aspects of civil law and criminal law. Almost all the courts of the country have followed that lead.

Mr. Coo was a member of the Ontario Civil Rules Committee for almost 20 years, chair of certain of its sub-committees, a member of the Committee that wrote the new Ontario Civil Rules and Chair of the Sub-Committee that wrote the Simplified Procedure Rule and system for the Court.

Mr. Coo was an active member of the Ontario Joint Committee on Court Reform throughout that Committee's life in its efforts over a number of years to speed up the litigation process, to make it less expensive and more efficient and effective.

Mr. Coo has been active for well over 30 years in speaking to and appearing before seminars and meetings throughout Canada, the United States and the Caribbean organized by the National Judicial Institute, the Canadian Bar Association the Advocates Society, the Criminal Lawyers Association, the University of Toronto and the United States Government (with the aid of the National Center for State Courts).

Mr. Coo is a member of the Ontario Review Board and the Ontario Consent and Capacity Board. He is also on the roster for the International Cooperation Group National Judicial Institute, a government-sponsored consulting group to foreign governments on developing and improving judicial systems.

He was a prime mover in the introduction of computers into the Ontario justice system and was a member for some years of the Judges Computer Advisory Committee of the Canadian Judicial Council, which serves the national interests of all superior and appellate court judges. He was also a member of the Toronto Judges Technical Committee.

Mr. Coo was, from the beginning, a member of the Judicial Committee of the Integrated Justice Project and was a member of the Executive Steering Committee of that project.

Mr. Coo was one of the founding members and a first director in Ontario and is a continuing member and past Director of the Canadian Judges Conference, a national organization of superior court judges.