Mary M. Thomson

One of Canada's pre-eminent litigators, Mary Thomson serves as head of Gowling WLG's national Litigation & Dispute Resolution Group and is past leader of its Product Liability Group. Over the past three decades, she has represented clients in many of the country's highest-profile legal matters in her field of expertise, including class actions and mass tort litigation, public inquiries, and before administrative tribunals.

Mary has appeared in courts across Canada on matters involving product liability, particularly involving pharma and medical devices as well as consumer products generally. She is a recognized expert in health law, consent law, privacy law and related matters.

Mary has been repeatedly singled out as a top legal practitioner by Chambers Canada, Canadian Legal Lexpert Directory, The Best Lawyers in Canada and other leading directories. In 2013, she was awarded the prestigious Lexpert Zenith Award for her extraordinary leadership in the legal profession.

In addition to her legal practice, Mary has taught trial advocacy and negotiation theory throughout her career. For more than a decade, she was an adjunct professor in the graduate department of the Faculty of Medicine at the University of Toronto, instructing in ethical and legal issues related to health law.

Mary is past chair of Outward Bound International (2011-2017), and was previously chair of Outward Bound Canada. She has chaired the Selection Committee (ON) for Pearson College, a United World College, for many years.

Career & Recognition

Filter timeline:


  • American Society of Law, Medicine & Ethics
  • Canadian Bar Association
  • Canadian Institute for the Administration of Justice
  • Defense Research Institute
  • The Advocates' Society

Mary has authored a number of articles and papers on a variety of topics, including contributing a chapter to Law and Ethics in Biomedical Research: Regulation, Conflict of Interest, and Liability, published by University of Toronto Press, 2006, and Lies, Damned Lies and Statistics: The Use of Statistical Evidence in Criminal and Civil Law, published in the proceedings of the Canadian Institute for the Administration of Justice, 2000.

Mary is a sought-after speaker in her areas of legal expertise.

Representative Work

Class Actions

  • Lead counsel for a major pharmaceutical client with respect to a diabetes medication.
  • Lead counsel for the manufacturer of a leading dental adhesive.
  • Lead counsel for major standards organization with respect to modular home claims.
  • From 2004 to 2009, lead counsel for a major pharmaceutical client with respect a leading coxib medication.
  • Lead counsel and national coordinating counsel for a major pharmaceutical client with respect to bisphosphonate litigation based in Saskatchewan.
  • Lead counsel for a leading energy drink manufacturer.
  • Lead counsel in a tuberculosis notification case including successfully defeating plaintiffs' claims for mental distress.
  • Lead counsel on a major privacy breach class action for a public entity.
  • Senior counsel to local litigation teams on diagnostic-related class actions, responsible for strategy and outcomes on class certification matters.

Mass Torts

  • Counsel to all physicians in Canada with respect to Krever Inquiry and "blood litigation" throughout the 1990s.
  • Trial counsel on Canadian litigation involving transfusion associated AIDS and related HBV, HCV claims.
  • Responsible for product recall and patient notification regarding surgical instrumentation and possible transmission of infectious diseases.
  • Act for a number of manufacturers of medical devices and pharmaceutical products with respect to threatened litigation.