Colleen M. Hennessey

Colleen is an experienced trial lawyer with over 30 years of experience defending clients in high stakes litigation including: product liability, class actions, mass torts and health care litigation. She regularly serves as national counsel, regional counsel and science counsel defending clients in coordinated state court proceedings, multi-district litigation (MDLs) and single plaintiff cases involving complex scientific, medical and regulatory issues.  She has represented numerous pharmaceutical and medical device manufacturers as well as healthcare organizations and healthcare providers.

Colleen has extensive experience defending healthcare providers against claims of negligence, personal injury, wrongful death and defamation.  She has advised healthcare providers facing claims of negligence and professional misconduct before various administrative licensing boards.

Colleen defends retailers in products liability matters involving a vast array of products as well as claims investigations that require immediate investigation and expert evaluation.

Colleen utilizes her litigation experience and knowledge of the healthcare industry to conduct litigation risk assessments and counsel clients on risk mitigation strategies to avoid litigation.

• American Bar Association
• Boston Bar Association
• Defense Research Institute
• Women’s Bar Association
• International Association of Defense Counsel

• American Conference Institute, GLP-1 Law & Policy Summit, Mass Torts, Pharmacovigilance, and the Litigation Outlook for GLP-1 Drugs (July 24, 2025).
• Lawyers for Civil Justice, Annual Meeting, The Accutane Decision and the Daubert Factors (December 2018)
• American Conference Institute, Drug and Medical Litigation Conference, Training the Next Generation of Life Sciences Attorneys to Become an Asset – Deposition Practice (December 2017)
• American Conference Institute, Women Leaders in Life Sciences Law, Year in Review: 2016-2017 Legal Updates by Practice Area (July 2017)
• American Conference Institute, Women Leaders in Life Sciences Law, What Women Leaders in the Life Sciences Law Must Know about Products Liability, Mass Torts, and “Bet-the-Company” Litigation (July 2016)
• Boston Bar Association, Multidistrict Litigation from the Plaintiff, Defense, and Judicial Perspectives (April 2016)
• American Conference Institute, Drug and Medical Litigation Conference, Preparing the Next Generation of Leaders of the Defense Bar- Strategy and Trial Advocacy Deep-Dive (December 2015)

• Secured case-ending rulings for pharmaceutical manufacturer in mass tort proceeding of over 8,000 cases alleging permanent gastrointestinal injuries.
• Coordinated the successful defense of national litigation in state and federal courts on behalf of pharmaceutical manufacturer whose product was alleged to have caused suicide and psychiatric injury.
• Defended pharmaceutical manufacturer in the defense of individual and class action proceedings asserting claims for permanent neurological injuries and medical monitoring.
• Defense of global retailer in multi-plaintiff product liability litigation alleging that plaintiffs developed cancer from consumer talcum powder products.
• Obtaining summary judgment, affirmed by  Nebraska’s Supreme Court, on behalf of pharmaceutical manufacturer after successful exclusion of experts at Daubert hearing.
• Trial counsel for pharmaceutical manufacturer in state consolidated proceedings obtaining first defense verdict in multi- plaintiff litigation.
• Represented pharmaceutical manufacturers in claims brought under the False Claims Act and state consumer protection statutes  seeking damages relating to reimbursement for pharmaceuticals under Medicare and Medicaid.

• Senior Fellow, Litigation Counsel of America
• Best Lawyers, Product Liability Litigation – Defendants, since 2022