Mark D. Cahill

Mark Cahill, a partner since 1992, focuses on bringing creativity and practical business judgment to his litigation practice, which includes disputes arising from mergers and acquisitions, sophisticated insurance coverage claims and analysis, corporate finance and governance matters, class actions and other complex business litigation.

He was named "Best Lawyer" in Boston for Insurance Law by Best Lawyers 2018. He is listed in Chambers USA, The Legal 500, Best Lawyers in America and is named a Massachusetts Super Lawyer.

Practice Focus

Complex Business Litigation:  represents public and private companies and venture capital and private equity firms, as plaintiffs and defendants, in intellectual property, complex financial, class action and contract litigation.

Insurance & Reinsurance Litigation:  substantial experience in the areas of insurance coverage, bad faith, extra-contractual claims and reinsurance issues.

Lead counsel:  Mr. Cahill has tried numerous jury and bench cases in federal and state courts, and arbitrations in various alternative dispute resolution forums.  He also has argued appeals before the Massachusetts Supreme Judicial Court, Appeals Court and the US Court of Appeals.  Mr. Cahill regularly handles matters in courts throughout the country.

Representative Engagements

  • Obtained defense verdict following two week jury trial in $120 million extracontractual and bad faith suit against major insurer.
  • Prosecuted breach of financial warranty and fraud claims against, and obtained eight figure settlement from, sellers of various private manufacturing companies.
  • Successfully defended international company against self-dealing claims brought by minority shareholder in $150 million business valuation dispute in which, after one week trial, the minority shares were valued at less than ten percent of amount sought.
  • Led appellate team in overturning multimillion dollar bad faith award against major insurer.
  • Following one week trial, obtained defense judgment finding that business plaintiff failed to prove causation of any damages in misappropriation of trade secrets case where default judgment had been entered against defendants when represented by predecessor counsel.
  • Obtained summary judgments in favor of national insurance clients in numerous declaratory judgment actions involving various coverage, insurance policy rescission and extra-contractual issues.
  • Successfully defended against consumer class action cases brought against international manufacturer of computer products.
  • Obtained defense verdict and seven figure jury award of compensatory and punitive damages on counterclaim against party who breached letter of intent in business purchase transaction.

Publications and Presentations

  • “Expert Testimony is Key in RMBS Liability,” co-author, Insurance Law360, March 2013.
  • “The Nuances of D&O Dishonesty Exclusions,” co-author, White Collar Law360, November 2010.
  • “Deals on the Rocks,” author, The Deal, January 2009.
  • “Tort Liability for Insurance Inspections: Case Law and Recent Developments,” co-author, Coverage, September/October 2008.
  • “Litigation In The Digital World: Practical Tips For Corporate Counsel Dealing With The New E-Discovery Rules,” Association of Corporate Counsel Quarterly Newsletter, July 2007.

Professional and Community Involvement

Mr. Cahill is a member of the Firm’s Ethics Committee and has served as a member of the Firm’s Executive Committee, as chairman of the Litigation Department and as the Firm’s Hiring Partner. 

Mr. Cahill is a member of the Boston Bar Association, serves as a mentor for minority law students and has served as a member of the Council of Advisors for Volunteer Lawyers for the Arts.  He is a member of the Board of Overseers of Summer Search Boston.  Mr. Cahill participates in his community as an AFS sponsor, charity fundraiser and as a member of Old Ship Church in Hingham, Massachusetts.  He served as a Trustee of Derby Academy and as Chair of the Board’s Committee on Trustees for twelve years.

Education & Credentials

Drake University Law School
JD, 1984, with highest honors, Order of the Coif
Rutgers University
AB, 1980



U.S. District Court, Massachusetts

U.S. Court of Appeals, First Circuit