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Ad. E.

Marie Cossette, Ad. E.

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Direct line:
418 266-3073

418 688-3458



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

A significant component of her practice is devoted to public law, administrative law and disciplinary law. She acts regularly in matters raising issues of State relations with various parties and in different forms. She advises public bodies and government corporations in proceedings before various courts and tribunals. In particular, she has developed strong expertise relating to commissions of inquiry, having acted as senior counsel to the Gomery Commission, assistant chief counsel to the Johnson Commission, and counsel to the Quebec provincial police officers during the Poitras Commission. She currently represents a major public contracting authority before the Charbonneau Commission. She was recently prosecutor for the coroner’s office during the public inquiry regarding the fire at the Résidence du Hâvre in L’Isle Verte. She also acts for various professional orders and professionals in disciplinary and penal investigations and with respect to administrative governance issues.

A second component of Ms. Cossette’s practice is focused on construction law litigation. She advises both private and public sector clients in procurement, tendering and contracting matters on claims, calls for tenders, defects and poor workmanship, the professional liability of industry participants, and other related subjects. These matters raise a wide variety of technical issues and often require the administration of complex expert evidence.

Through her work in these two areas of practice, Ms. Cossette has acquired extensive experience on ethical questions, professional conduct and integrity issues, particularly in construction. She is also the head of the firm's Corporate and Business Integrity Practice Group, which she set up in concert 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, misappropriation of business opportunities, etc.).

Concurrently with these more traditional practice areas, Ms. Cossette has also developed an expertise in managing media relations in litigious matters. She has worked closely with public relations firms, teaming with her clients to ensure their rights are respected, while providing them with an understanding of public relations imperatives. Hand in hand with this experience, she has practical knowledge of the workings of the print media, television and radio. She acts regularly as a legal analyst for the Réseau de l’Information (RDI) and la Société Radio-Canada — the French wing of the CBC.

Ms Cossette has contributed, as panelist, author or co-author, to various conferences and publications dealing with the functioning of commissions of inquiry, the role of commission counsel, communications issues, crisis management, disciplinary law and integrity issues.

She is coordinator of the Administrative Law Group at the firm's Quebec City office. She is also a member of the firm’s Professional Development Committee and heads the United Way campaign in the Quebec City offices.

Ms. Cossette was awarded the title of Emeritus Lawyer (Ad.E.) by the Quebec Bar in 2014.


Representative mandates

  • Analyst for Radio-Canada and the Réseau de l'information (RDI) on legal matters generally, commissions of inquiry and integrity issues.
  • Client support on ethical, governance and integrity issues;
  • Client support for crisis management and media relations;
  • Legal counsel to the coroner’s office in the context of the public inquiry into the burning of the Résidence du Hâvre at L’Isle Verte.
  • Counsel to four highly publicized commissions of inquiry (Charbonneau Commission, Gomery Commission, Johnson Commission and Poitras Commission);
  • Independent counsel to the Judicial Council in the context of the public inquiry respecting Mr. Justice Michel Girouard.
  • One of the lawyers representing Commissioner Gomery, in his capacity as commissioner, before the Federal Court concerning the judicial review of certain conclusions in his report;
  • One of the lawyers acting for the Honourable Chief Justice François Rolland before the Supreme Court of Canada concerning a constitutional challenge of the rules of practice governing media activities in courthouses;
  • One of the lawyers representing a large law firm in a proceeding involving several million dollars arising from a financing that was found to be fraudulent;
  • Representation in relation to commercial arbitrations (shareholder agreements, termination of commercial lease, intellectual property in connection with research projects);
  • Representation in matters involving the duty of loyalty and the misappropriation of business opportunities by former corporate directors;
  • Representation of engineers in professional liability proceedings;
  • Representation in construction law and procurement and tendering matters on behalf of major public and private sector clients (claims, defects and poor workmanship, performance bonds, contestation of contract award decisions);
  • Representation in civil liability class-action suits;
  • Representation before disciplinary boards and in penal matters on behalf of several professional orders and professionals.

Some recent interviews

  • Participation in various television and radio interviews with Radio-Canada (the French wing of the CBC) as a commentator on the trial of the former Lieutenant-Governor of Quebec, Lise Thibault (2014-2015);
  • Participation in various television interviews with Radio-Canada to discuss the status of the proceedings of the Special Commission investigating the events of the spring of 2012 in Quebec (2013);
  • Participation in various television interviews with Radio-Canada and in the election night coverage as a commentator on the municipal elections (2013);
  • Participation in the program Champ Libre (Radio-Canada) to discuss the class action being organized against a Hamilton company (2013);
  • Participation in various television and radio interviews with Radio-Canada to discuss the stakes involved in setting up a public commission of inquiry on the construction industry and on the issues the Charbonneau Commission will be facing (2011);
  • Main analyst for RDI concerning the work of the Oliphant Commission (2009)
  • Speaker at the conference on investigative bodies organized by the CBA: "The Role and Challenges of Commission Counsel" (2009)
  • "The Role and Challenges of Commission Counsel", CBA conference on investigative bodies, Éditions Yvon Blais, Actes de la formation juridique permanente 2009, volume 6 (2009)
  • Participation in the drafting of the Summary of Professional Law, Éditions Yvon Blais (2007).

Presentations and conferences

  • Honorary President at the 4th International Congress of Fire Investigators (2015)
  • Speaker for the disciplinary law theme day at the Conference on Advanced Training in Administrative Law, Canadian Institute: “Top ten cases in disciplinary law – 2014” (2015)
  • Panelist at the opening workshop of the 71st Association des constructeurs de routes et grands travaux du Québec annual conference: “Let’s Build the Present” – discussing the legal, ethical and media issues facing the construction industry (2015)
  • Panelist at two Ordre des ingénieurs du Québec breakfast conferences: “The engineer’s responsibility: as a professional, how can an engineer take action in a regulated context?” (2015)
  • Lecturer at the annual congress of the CNNAR on the subject of investigative techniques in disciplinary matters (2014)
  • Lecturer at the training session entitled “La lutte contre la corruption au Québec, au Canada, aux États-Unis et à l’étranger” [Fighting corruption in Quebec, Canada and abroad], The Canadian Institute: “What is in your file? How to conduct a risk assessment?”(2014)
  • Speaker and chairperson for the disciplinary law theme day at the Conference on Advanced Training in Administrative Law, Canadian Institute, : "General Principles of Regulatory Investigations and Application to Disciplinary Investigations" and a presentation on: “Updates and changes to disciplinary sanctions”  (June 2014)
  • Speaker for the Quebec Bar: "Status report on the anti-corruption provisions introduced by Bill 1: was the objective achieved?" (2014)
  • Moderator for a debate on the subject of integrity organized by the Quebec Order of Engineers in connection with the election campaign (2014)
  • 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 at a symposium on commissions of inquiry organized by the CBA: “The Role and Challenges of Counsel to the Commission" (2009);
  • 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," TheLaw 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

  • Ambassador for the Cultural Council for the Cultural Participation of Young People (2014 - )
  • 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)
  • Chair of the United Way Committee 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)

Professional affiliations

  • 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)