Lepofsky graduated in 1979 with honours from Osgoode Hall Law School with a Bachelor of Laws. He obtained a Masters of Law from the Harvard Law School in 1982. He was admitted to the Ontario Bar in 1981. From 1982 to the end of 2015, he practised law in Toronto with the Ontario Ministry of the Attorney General, in the areas of constitutional, civil, administrative and most recently, criminal law. In 2004, he was appointed to the position of General Counsel. This is the highest promotion in the Ontario Public Service. Reserved for only a handful of the 2,000 lawyers in the Ontario Public Service, it is reserved for the most senior counsel, to recognize career achievement in handling the most complex work, demonstrated diversity of expertise, creativity, professional leadership, judgement, and mentoring/role modelling. From 1982 to 1988, he served as counsel in the Crown Law Office Civil, conducting civil, administrative and constitutional litigation on behalf of the Ontario Government. From 1989 to 1993, he served as counsel in the Constitutional Law and Policy Division, conducting constitutional litigation on the Government’s behalf. From 1993 to the end of 2015, he served as counsel in the Crown Law Office Criminal, conducting criminal appeals in the Ontario Court of Appeal and the Supreme Court of Canada. He has appeared on at least 30 cases in the Supreme Court of Canada in his career, as counsel or co-counsel, and in some 200 cases in the Ontario Court of Appeal. He retired from his position with the Ontario Public Service at the end of 2015. Since 1991, he has served as a part-time member of the University of Toronto, Faculty of Law, where he teaches an advanced constitutional law seminar on freedom of expression and press. From 1987 to 2005, he served as Associate Head of the Ontario Bar Admission's Course's Public Law Section. Starting in January 2016, he serves as a part-time visiting professor of legal ethics and public interest advocacy on the faculty at the Osgoode Hall Law School. He was a founding member of, and served as co-chair of Barrier-Free Canada, a community coalition that advocates for the enactment of a national Canadians with Disabilities Act. Starting in April 2015, he now serves as a member of the Toronto District School Board's Special Education Advisory Committee. In January 2016 he became its chair. That legally-mandatory committee advises the Toronto District School Board on reforms needed to improve special education services and programs. Canadian Lawyer Magazine listed Lepofsky among Canada's 25 most influential lawyers. He is the author of one law book, and the author or co-author of 30 law journalarticles or book chapters on topics including constitutional law, criminal law, administrative law, human rights, and the rights of persons with disabilities. His publications have been cited with approval in several decisions of the Supreme Court of Canada, as well as by trial and appeal courts across Canada. He has lectured on topics including these across Canada, and in the U.S., Israel, the Republic of Ireland, Denmark and Belgium.