Marie CossetteAd. E.

Partner / Québec
Telephone 418 266-3073
Fax 418 688-3458



Marie Cossette was called to the Quebec Bar in 1991 and joined Lavery in 2011.

She is a partner and heads Lavery’s business integrity group, and the Administrative law group of Lavery’s Québec City office. She has several years of experience in major litigation cases. A significant component of her practice is devoted to public law, administrative law, and disciplinary law. She is regularly called to work on cases involving  government relations in various forms. 

She has developed expertise relating to public inquiries (Charbonneau Commission, Johnson Commission, Gomery Commission, Poitras Commission and Chamberland Commission.) She recently served as counsel for the coroner’s office during the public inquiry into the fire at the Résidence du Hâvre in L’Isle Verte. In addition, she recently acted as independent counsel for the Canadian Judicial Council during the public inquiry into the conduct of the Honourable Michel Girouard. She also acts for various professional orders and professionals during disciplinary and penal investigations and with respect to questions of administrative governance.

A second component of Ms. Cossette’s practice involves business and construction law. These cases raise a wide variety of technical issues and require the taking of often complex expert evidence. Through her work in these two areas of practice, Ms. Cossette has acquired extensive experience with issues involving ethical questions, professional conduct, and integrity, particularly in the field of construction.

Concurrently with these more traditional practice areas, Ms. Cossette has developed expertise in managing media relations during media crisis management and court cases. She has worked closely with public relations firms to ensure that her clients’ rights are respected while ensuring that they understand public relations imperatives. She also has practical knowledge of the workings of the print, television, and radio media and regularly serves as a legal analyst for the Réseau de l’Information (RDI) and Société Radio-Canada.

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

In 2017, The Canadian Legal Lexpert® Directory listed her in the fields of Litigation and Public Law.

In 2014, Ms. Cossette was awarded the title of Advocatus Emeritus (Ad. E.) by the Quebec Bar.

Representative mandates

  • Analyst for Radio-Canada and the Réseau de l'information (RDI) on legal matters  in general, commissions of inquiry, and integrity issues
  • Client support regarding ethical, governance and integrity issues
  • Client support in matters of crisis management and media relations
  • Counsel to five highly publicized commissions of inquiry (Chamberland, Charbonneau, Gomery, Johnson and Poitras)
  • Independent counsel for the Canadian Judicial Council during the public inquiry into the conduct of the Honourable Michel Girouard
  • Legal counsel to the coroner’s office during the public inquiry into the fire at the Résidence du Hâvre in L’Isle Verte
  • One of the lawyers acting for the Honourable Chief Justice François Rolland before the Supreme Court of Canada during a constitutional challenge of the rules of practice governing media activities in courthouses
  • Representations in cases involving construction law and tendering matters on behalf of major public and private sector contractors (claims, faults and defects, performance bonds, contracting disputes, termination)
  • Representations on commercial arbitration (shareholder agreements, termination of commercial lease, intellectual property in connection with research projects)
  • Representations on the duty of loyalty and the misappropriation of business opportunities by former corporate directors
  • Representations in civil liability class-action suits
  • Representations before disciplinary boards and in penal matters on behalf of several professional orders and professionals


  • “Understanding the organization and functioning of commissions of public inquiry to better influence them,” Annual Convention of the Barreau du Québec, 2010
  • "Status and Role of Commission Counsel," co-authored with Simon Ruel, The Law of Public Inquiries in Canada, Carswell, 2010
  • Revision of manuscript of The Law of Public Inquiries in Canada by Simon Ruel, Carswell, 2010
  • "The Role and Challenges of Commission Counsel", Proceedings of the 2009 CBA continuing education symposium on Commissions of Inquiry, volume 6, 2009
  • "Appropriation of a Business Opportunity: Liability of Senior Management", co-authored with Marc-André Sansregret, National Magazine of the Canadian Bar Association and CBA PracticeLink, 2009
  • Helped draft the Précis de droit professionnel (Summary of Professional Law), Editions Yvon Blais, 2007


  • Moderated a conference on construction law organized by Lavery (2017)
  • Co speaker for the Association des estimateurs et des économistes de la construction du Québec (AEÉCQ) : Présentation de la Loi favorisant la surveillance des contrats des organismes publics et instituant l’Autorité des marchés publics (Bill 108) (2017)
  • Speaker and President of the day in disciplinary law, Open Forum : Le rôle du conseil d’administration d’un ordre professionnel à la lumière du Projet de loi 98 (2017)
  • Panelist for the regroupement des jeunes chambres de commerce (RCCQ) : La force du réseau en gouvernance (2017)
  • Speaker at the Congrès de la CEGQ :  La résiliation unilatérale d’un contrat de construction par le client: les enjeux pour chaque partie (2017)
  • Speaker at Lavery’s  construction law conference: “Bill 108: What You Should Know About the Autorité des marchés publics” (2016)
  • Moderated a debate on “Limits to Professionals’ Freedom of Expression, ABC Québec” (2016)
  • Speaker at the Femmes en finances, femmes en action seminar on women and ambition (2016)
  • Organizer and speaker during the conference on Corporate and business integrity organized by Lavery, Comment gérer la crise à l’externe, 2016
  • Speaker and President of the day in disciplinary law, Open Forum: “The Top ten decisions in disciplinary law”, 2016
  • Speaker at four workshops of the Colloque des dirigeants des ordres professionnels: Votre Ordre vit une crise médiatique : sauriez-vous y faire face? [Your Order is going through a crisis: would you know how to tackle it?], 2015
  • Honorary chair of the 4th International Congress of Fire Investigators, 2015
  • Speaker during the disciplinary law day of 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 annual conference of the Association des constructeurs de routes et grands travaux du Québec : “Let’s Build the Present” – identifying the legal, ethical, and media issues facing the construction industry, 2015
  • Panelist at a breakfast meeting of the Ordre des ingénieurs du Québec:  “The engineer’s responsibility: as a professional, how can an engineer act in a regulated environment?”, 2015
  • Participation in various Radio-Canada television and radio interviews as commentator on the trial of Lise Thibault, the former Lieutenant-Governor of Quebec, 2014 to 2015
  • Lecturer at the annual conference of the CNNAR on the subject of investigative techniques in disciplinary matters, 2014
  • Lecturer at the training session “Fighting corruption in Quebec, Canada, and abroad,” The Canadian Institute: “What is in your file? How to conduct a risk assessment”, 2014
  • Speaker and chair during the disciplinary law day of the Conference on Advanced Training in Administrative Law, Canadian Institute. Presentation: "General Principles of Regulatory Investigations and Application to Disciplinary Investigations" and speech: “Updates and changes to disciplinary sanctions”, June 2014
  • Speaker for the Barreau du Québec: "Status report on the anti-corruption provisions introduced by Bill 1: was the objective achieved?", 2014
  • Moderator of a debate on the subject of integrity organized by the Ordre des ingénieurs du Québec in connection with the election campaign, 2014
  • Speaker for the Fédération Québécoise des Municipalités:  “Is your municipality prepared to manage a media crisis?”, 2013
  • Participation in various Radio-Canada television interviews on the proceedings of the Special Commission investigating the events of spring 2012, 2013
  • Participation in various Radio-Canada television interviews and during election night coverage as commentator on the municipal elections, 2013
  • Participation in the Radio-Canada program Champ Libre discussing the class action suit against a Hamilton company, 2013
  • Workshop presenter at the plenary meeting of the annual convention of the Barreau du Québec: “Politics in the post-corruption era: utopia or hope?”  2013
  • Speaker at the annual convention of the Barreau du Québec: “When a “No-comment!” answer is not enough: The lawyer’s role in crisis management”, 2013
  • Organizer, honorary co-chair, and speaker at the Insight symposium “Crisis Management: The legal advisor’s survival guide”: “The lawyer and public relations officer team – Respective roles and the importance of complementarity”, 2012
  • Co-speaker at a risk management symposium organized by Lavery: "Precautions to take with regard to lobbying and relations with public authorities", 2012
  • Speaker at the annual convention of the Barreau du Québec: "Media management in times of crisis and litigation", 2012
  • Speaker at a symposium on managing litigation risks organized by Lavery: “Communicating with the media: challenges and benchmarks”, 2011
  • Participation in various Radio-Canada television and radio interviews on the launching of a public commission of inquiry into the construction industry and the issues facing the Charbonneau Commission, 2011
  • Main RDI analyst conderning the work of the Oliphant Commission, 2009
  • Speaker at a symposium on commissions of inquiry organized by the CBA: “The Role and Challenges of Commission Counsel", 2009
  • Speaker for the Ordre des ingénieurs du Québec (Québec City and Chaudière-Appalaches division) and the Science & Engineering Faculty of Université Laval: “Lessons to be Learned from the Johnson Commission”, 2008

Professional and community activities

  • Interviewed about journalistic leaks at the UPAC (24h60) (2017)
  • Interviewed about police investigations and the duplication issue of a public inquiry (Sous la loupe) (2017)
  • Interviewed about the new public inquiry on protecting the confidentiality of journalistic sources (Sous la loupe) (2016)
  • Interview with RDI to discuss political immunities (2016)
  • Leader for the Québec cohort of Effect A Women and Ambitions, 2016
  • Honorary Chair of the fundraising campaign of the contemporary music group ECM+ Montréal, 2016
  • Member of the board of directors of the Fondation du Musée National des Beaux-Arts (2016 - )
  • Chair of the Fundraising Committee for scholarships at Externat St-Jean Berchmans and Honorary Chair for the 2016 campaign, since 2016
  • Ambassador for the Cultural Council for the Cultural Participation of Young People since 2014
  • Member of the board of directors of the Chambre de commerce et d’industrie de Québec, since 2013
  • Member of the Organizing Committee for the 2013 convention of the Barreau du Québec, 2012 to 2013
  • Chair of the United Way committee at Lavery’s Québec City office, 2012 to 2015
  • Member of the Comité Affaires-Culture for the Chambre de commerce de Québec, since 2012
  • Member of the Canadian Bar Association's Communications committee, since 2009
  • Member of the Executive Council of the Québec branch of the Canadian Bar Association, 2011 to 2012
  • Member of the Bar of Montréal's Women in the legal profession committee, 2009 to 2010
  • Honourary chair of the fundraising campaign for Théâtre Le Périscope, 2011
  • Member of the Honourary committee for Théâtre La Veillée’s fundraising campaign, 2009 to 2010
  • Member of the Honour Roll of École Marie-Rivier (Drummondville Deschênes School Board) to encourage young people to pursue their studies, 2008


Legal 500 Canada 2017


  • LL.B. Civil Law, Université de Sherbrooke (Winner of the university’s Prix du Barreau award for the highest overall average among graduating students planning to join the Barreau du Québec)
  • Member of the Barreau du Québec since 1991 (Prix du Barreau, award given to some emeritus students)

Professional affiliations

  • Member of the Canadian Bar Association


  • Arbitrator
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