Marie Cossette has many years of experience with complex litigation files. A major component of Ms. Cossette's practice involves commercial and construction litigation. These cases raise a wide variety of technical issues and often involve managing complex expert evidence. Through her work in these areas of practice, Ms. Cossette has acquired extensive experience with issues relating to integrity, governance as well as ethical and professional conduct, particularly in the construction sector.

A second area of her practice covers public law, administrative law, professional liability and disciplinary law. She is regularly called to work on cases involving government relations in various forms. She has extensive experience relating to public inquiries (Chamberland Commission, Charbonneau Commission, Johnson Commission, Gomery Commission, and Poitras Commission). She served as counsel for the coroner's office during the public inquiry into a fire at the Résidence du Havre in L'Isle-Verte, Quebec. In addition, she acted as independent counsel for the Canadian Judicial Council during the public inquiry into Justice Michel Girouard. She also acts for various professional orders and professionals during disciplinary, professional liability (including for lawyers and engineers) and penal investigations as well as in matters concerning governance.

Concurrently with these more traditional practice areas, Ms. Cossette has experience managing media relations during media crisis and court cases. She has worked closely with public relations firms to ensure her clients' rights are respected while ensuring public relations imperatives are understood. 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 (Canadian broadcasters).