Ann Marie Duffy is an accomplished trial lawyer who has broad experience in the defense of complex civil litigation. With nearly 20 years of experience, Ann Marie has represented companies in some of their most significant cases on a variety of claims including commercial disputes, construction claims, products liability, environmental tort, fraud, and intellectual property claims. In one of the largest cases she has tried, Ann Marie served as second chair in a patent infringement trial in the United States District Court for the District of Delaware in a case where total damages exceeded $2 billion.

Ann Marie’s broad range of litigation experience includes working on highly complex cases with significant discovery and procedural issues. Her cases have routinely involved multi-national discovery efforts and extensive, in-depth investigations. Ann Marie also has extensive experience conducting comprehensive due diligence investigations for corporate transactions and negotiating and preparing complex agreements to protect commercial interests and facilitate compliance with private corporate obligations and governmental requirements.

In addition to her trial experience, Ann Marie has briefed and argued appeals to the United States Court of Appeals for the District of Columbia Circuit, the United States Court of Appeals for the Tenth Circuit, and the State of New York Supreme Court, Appellate Division Third Judicial Department.

Currently, Ann Marie is lead counsel for a producer of PTFE and silicone coated fabrics, tapes, and belts, defending against claims of negligence, trespass, and nuisance for its use and handling of materials containing trace amounts of PFOA. Ann Marie is also a trial team partner defending a major engineering, procurement, and construction (EPC) contractor against alleged breach of contract, professional negligence, and fraud claims arising from the design, engineering, and construction of a nearly $1 billion agrochemical plant in Arkansas Circuit Court.


George Washington University Law School (J.D., 2002) James Madison University (B.A., cum laude, 1999)


  • District of Columbia
  • Virginia
  • United States Supreme Court
  • United States Courts of Appeals for the Tenth, District of Columbia, and Federal Circuits
  • United States District Courts for the District of Maryland, Western District of Tennessee, Eastern District of Texas, and Eastern and Western Districts of Virginia


  • 2023 Annual M&A Advisor Awards Winner “Professional Services Deal of the Year”, Deal Team Member
  • Super Lawyers, Business Litigation, 2023


  • National Catholic Forensic League
    • President
    • Washington Dioceses Director
  • Washington Arlington Catholic Forensic League, Member
  • Washington, D.C. Chapter of Chief, Founding Member


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