John C. Calhoun

John Calhoun helps advise a wide range of clients, with particular emphases on patent/trade secret, securities, insurance, and general commercial litigation. In addition to representing clients at trial and throughout the litigation process, he also advises clients about how to avoid or resolve litigation risk in a cost-effective way.

Some of John’s notable clients include Hewlett Packard, Wells Fargo, Cisco, Swiss Re, Munich Re, Alnylam, and Foundation Medicine.

Prior to law school, John served as a Marshall Scholar at the University of Oxford, and as a Fulbright Scholar. He has also advised presidential, gubernatorial, and congressional administrations and campaigns on a range of legal and policy issues.

Representative Engagements 

  • Prevailed at summary judgment (including for costs) while representing a major private equity firm in a suit filed by the founder of an acquired company.
  • Prevailed in a First Circuit appeal while representing a major private equity firm on an issue related to a purchase agreement’s indemnity provisions.
  • Won at trial while representing an international insurer in successful action to rescind $25 million product contamination insurance policy based upon policyholder’s material misrepresentation of facts.
  • Prevailed on a motion to dismiss while representing the founder of a leading software firm in a board dispute.
  • Reached favorable settlement for law firm in a legal malpractice suit filed by a former client.
  • Reached favorable settlement for automotive parts manufacturer seeking indemnification from Chinese suppliers.
  • Reached favorable settlement for large U.S. bank in an OSHA-proceeding brought by an internal company whistleblower.
  • Extensive representation of private independent schools in investigating and remediating allegations of sexual misconduct.
  • Investigated internal company whistleblower complaint for international insurer.
  • Momenta Pharm., Inc. v. Amphastar Pharm., Inc. et al., D. Mass., Fed. Cir.: Trial counsel for Momenta Pharmaceuticals in patent infringement litigation relating to innovative methods of processing therapeutic polysaccharides.
  • Guardant Health, Inc. v. Foundation Medicine, Inc., D. Del.: Counsel for Foundation Medicine in patent infringement litigation relating to next generation sequencing analysis.
  • Alnylam Pharmaceuticals, Inc. v. Dicerna Pharmaceuticals, Inc., D. Mass.: Counsel in trade secret misappropriation lawsuit brought against Dicerna Pharmaceuticals.

Publications and Presentations

Professional and Community Involvement

  • Member of the Boston Bar Association
  • Member of the American Bar Association
  • Member of multiple business and charitable boards, including the Connecticut Policy Institute, Give a Summer, the Match Charter School Network, and Firoz Academy
  • Through Choate’s pro bono program, John represents special needs children to help them secure appropriate educational services


  • The Legal 500 (2024)

Education & Credentials

Yale Law School
JD, 2015

Editor, Yale Law Journal

Managing Editor, Yale Journal of International Law

Oriel College, University of Oxford
MSc, 2012, with honors

University of York
MA, 2011, with honors

University of Richmond
BA, 2009, summa cum laude, Phi Beta Kappa 


U.S. Court of Appeals, First Circuit

District of Massachusetts


John's Insights