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Marie Cossette was called to the Quebec Bar in 1991 and joined Lavery in 2011. She has numerous years of experience in handling major cases in various areas of litigation. 


A significant part of her practice is devoted to public law, administrative law and disciplinary law. She his regularly called upon to work in matters involving relations with the State under various forms. She provides advice to public organizations and government corporations before various forums. She acquired a particular expertise in public commissions of inquiry and acted as Senior Counsel for the Gomery Commission, as Assistant Chief Counsel for the Johnson Commission and as Counsel for the Officers of the Sûreté du Québec during the Poitras Commission. She currently represents a major public entity before the Charbonneau Commission. She also acts for various professional corporations and professionals in the context of disciplinary and penal investigations and for the purpose of dealing with administrative governance issues.


A second part of Ms. Cossette’s practice is focused on the area of construction law litigation. She provides advice to clients of both the private and public sectors respecting claims, calls for tenders, defects and faults, issues involving the professional liability of industry participants and other related subjects. These matters raise various technical aspects and require often complex expert evidence.


Through her work in these two areas of practice, Ms. Cossette has acquired extensive experience in issues relating to ethics, professional conduct and integrity, particularly in the field of construction. She is, moreover, the head of Lavery’s Corporate and Business Integrity Practice Group, which she set up in conjunction with the firm’s management.


Lastly, Ms. Cossette represents many clients in various commercial litigation matters (arbitration, commercial leases, shareholder agreements, intellectual property in the context of research projects, unpaid commissions and services, manufacturing defects, commercial fraud, business opportunity appropriations, etc.).


Concurrently with these more traditional practice areas, Ms. Cossette also developed an expertise in managing media relations in litigation cases. She has worked closely with public relations firms, with which she partners to monitor that her clients’ rights are enforced, while ensuring an understanding of public relations requirements. Together with this experience, she has practical knowledge of printed, television and radio media matters. She is regularly called upon to serve as a legal analyst for the Réseau de l’Information and Société Radio-Canada.


Ms Cossette has authored or co-authored several conferences and publications on the operation of public inquiries, the role of counsels in these commissions, the challenges raised by communicating as well as crisis management.


Ms. Cossette is articling principal and Coordinator of the Quebec City office Litigation Group. She is also a member of the firm’s Professional Development Committee and chairs the Centraide campaign in the Quebec City office. 


Representative mandates

  • Analyst for Radio-Canada and Réseau de l'information (RDI) for legal matters and commissions of inquiry;
  • Support of client in crisis management and media relations;
  • Counsel for four commissions of inquiry (Charbonneau Commission, Gomery Commission, Johnson Commission and Poitras Commission) that received a tremendous amount of media coverage;
  • One of the lawyers representing Commissioner Gomery, es qualities, before the Federal Court for the judicial review of certain conclusions in his report;
  • One of the lawyers for the Honourable Chief Justice François Rolland before the Supreme Court in a matter of constitutional challenge of the rules of practice concerning the activities of the media in courts of law;
  • One of the lawyers representing a large-scale law firm in a proceeding of numerous millions of dollars further to a fraudulent financing;
  • Representations in the context of commercial arbitration (shareholder agreement, commercial lease termination, intellectual property in the context of research projects);
  • Representations in matters of the duty of loyalty and the appropriations of businesses opportunities by former directors of companies;
  • Representations for engineers in matters involving professional liability;
  • Representations in the context of construction law and calls for tenders matters for major clients of both the public and private sectors (claims, defects and faults, bonds, contestation of the grant of contracts);
  • Representations with respect to civil liability class actions;
  • Representations before disciplinary councils and in penal matters.


Some interviews


Presentations and conferences

  • Speaker for the Fédération Québécoise des Municipalités: “Is your municipality ready to manage a media crisis?” (2013);
  • Workshop presenter at the plenary meeting of the Annual Congress of the Quebec Bar entitled: “Politics in the post corruption era: utopia or hope?” (2013);
  • Speaker at the Annual Congress of the Quebec Bar: “When a “No-comment!” answer is not enough: The lawyer’s role in crisis management”) (2013);
  • Organizer, honorary co-chairperson and speaker at the symposium entitled “Crisis Management: The legal advisor’s survival guide” by Insight: “The lawyer and media liaison officer duo – Roles and the importance of complementarity” (2012);
  • Co-speaker at a symposium on Risk Management organized by Lavery, de Billy: "Precautions to take with regards to lobbying and relations with public authorities" (2012);
  • Speaker at the Annual Congress of the Quebec Bar: "Media management in times of crisis and litigation" (2012);
  • Speaker at a symposium on “Managing Litigation Risks” organized by Lavery, de Billy: “ Communicating with media : challenges and markers” (2011);
  • Speaker for the Quebec Bar and the Quebec City Bar called "How to identify invisible barriers for women in the legal profession," for International Women's Day (2010);
  • Speaker for the Women in the Legal Profession Committee of the Montreal Bar: "Communicating Effectively Using Your Personality" (2010);
  • Co-chair and speaker at the 4th annual symposium on Women in Law organized by Les femmes de carrière en interaction: "Communicating Effectively" (2009);
  • Speaker at a symposium on commissions of inquiry organized by the CBA: “The Role and Challenges of Counsel to the Commission" (2009);
  • Co-chair and speaker at a symposium on Women and Leadership organized by Les femmes de carrière en interaction: "Identifying and Overcoming Invisible Barriers" (2008);
  • Speaker for the Quebec order of professional engineers (Quebec City and Chaudière-Appalaches division) and the Science & Engineering Faculty of Université Laval: “Lessons to be Learned from the Johnson Commission” (2008).


Other publications

  • “Understanding the Organization and Operation of Public Commissions of Inquiry in Order to Achieve Greater Influence,” Annual Congress of the Quebec Bar (2010);
  • Co-author of the "Status and Role of Commission Counsel," The Law of Public Inquiries in Canada, Carswell (2010);
  • Review of the manuscript of The Law of Public Inquiries in Canada by Simon Ruel, Carswell (2010);
  • "The Role and Challenges of Counsel to the Commission", Proceedings of the 2009 CBA continuing education symposium on Commissions of Inquiry, volume 6 (2009);
  • Co-author of the "Appropriation of a Business Opportunity: Liability of Senior Management", The Canadian Bar Association's National Magazine and CBA PracticeLink (2009);
  • Helped draft the treatise “Précis de droit professionnel” (Summary of Professional Law), Editions Yvon Blais (2007).


Professional and community activities

  •  Member of the Board of Directors of the Chambre de commerce et d’industrie de Québec (2013- )
  • Member of the Réseau des Femmes d’affaires du Québec (2013 - )
  • Member of the Organizing Committee for the 2013 Congress of the Quebec Bar (2012-2013)
  • Centraide President for Lavery in Quebec City (2012- )
  • Member of the Comité Affaires-Culture for the Chambre de commerce de Québec (2012- )
  • Member of the Canadian Bar Association's Communications Committee (2009- )
  • Member of the Executive Council of the Quebec Branch of the Canadian Bar Association (2011-2012)
  • Member of the Bar of Montreal's Women in the Legal Profession Committee (2009-2010)
  • Honorary president of the financing campaign of the Théâtre Le Périscope (2011)
  • Honorary committee member for the Théâtre La Veillée fundraising campaign (2009-2010)
  • Member of the Honour Roll of Marie-Rivier School (Drummondville Deschênes School Board) to encourage young people to pursue their education (2008)



  • Member of the Canadian Bar Association


  • LL. B. Civil Law, University of Sherbrooke (Winner of the university’s Prix du Barreau du Québec prize for the highest overall marks among graduating students planning to join the Quebec Bar)
  • Member of the Quebec Bar since 1991 (Quebec Bar Prize)

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