André Marin graduated a Magna Cum Laude with First Class Honours from the National Program at the University of Ottawa Faculty of Law. He obtained his LL.L. in 1988 and his J.D. in 1989. Prior to studying law, he completed his Bachelor of Arts degree at Carleton University in Ottawa in 1985. He served as the Canadian military's first Ombudsman, as well as the director of the province's Special Investigations Unit. André was named Ontario's sixth Ombudsman in 2005.

Since his appointment, he has reorganized the office and refocused its resources on high-profile, systemic investigations into issues affecting millions of Ontarians, from newborn babies to property taxpayers to lottery players, through the creation of the Special Ombudsman Response Team (SORT).

Along with responding to some 27,000 individual complaints a year, and acting as closed meeting investigator in many municipalities, the office conducts systemic investigations using SORT, resulting in dramatic government reforms. André's pioneering work in conducting systemic administrative investigations has drawn the interest of the global ombudsman community. Through the “Sharpening Your Teeth” training course he developed in 2007, he has also shared his expertise in conducting systemic investigations with ombudsmen and administrative watchdogs around the world pioneering work in conducting systemic administrative investigations has drawn the interest of the global ombudsman community.

In 2014, Mr. Marin was recognized for the second year in a row as one of Canadian Lawyer magazine's "Top 25 Most Influential" lawyers in Canada. In 2013, in addition to the Canadian Lawyer magazine recognition, Mr. Marin was named as one of Toronto Life magazine's 50 most influential Torontonians. In 2012, he received the Canadian Bar Association's John Tait Award of Excellence, a national award which recognized that his “unwavering commitment to public service, his advocacy skills and legal acumen distinguish him as an outstanding legal professional,” according to CBA President Trinda L. Ernst. He was a 2012 inductee into the 2012 class of the University of Ottawa Faculty of Law’s Common Law Honour Society. As well, in 2012, Mr. Marin was honoured with the Ontario Bar Association’s Distinguished Service Award, recognizing his exceptional career achievements and contributions to the practice of law in Ontario.