Attorneys Peter S. Cowan

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shareholder | Manchester, NH

Peter is a partner in Sheehan Phinney’s Litigation Department and also chairs the firm’s Construction Litigation Practice Group. He regularly represents clients in civil litigation cases focusing on business and construction litigation. Peter has substantial experience in trade secret, restrictive covenant, fiduciary duty, consumer protection act, contract, misrepresentation, shareholder disputes and various business torts. In construction related litigation, he primarily represents design professionals but he also represents general contractors and owners. Peter has substantial trial and appellate experience in both state and federal court, and also has experience in arbitration and other forms of alternative dispute resolution.


Key Cases

  • Successfully defended former owner/high-level executive of a for-profit hospital group against a $2.4 million dollar contribution claim, limiting liability award to ten percent, later substantially reduced in settlement.
  • Successfully resolved $12 million federal lawsuit asserting claims of negligent design of renovated clean rooms.
  • Won $1.2 million arbitration award and attorney's fees in dispute involving the breach of a severance agreement with the founder of a Boston-based venture capital firm.
  • Achieved multi-million dollar settlement for several plaintiff investors against primary beneficiary of roughly $32 million Ponzi scheme.
  • Successfully resolved defense of misappropriation of trade secrets claim against founders of company engaged in the manufacture of speciality furnaces used to grow artificial sapphire crystals.
  • Obtained plaintiff’s jury verdict for a large, national environmental remediation contractor (while defeating $1 million counterclaim) in breach of contract case involving complex design issues associated with the installation of an impermeable membrane in a slurry trench.
  • Achieved over $5 million confidential settlement for minority shareholder in Massachusetts breach of fiduciary duty case.
  • Obtained defendant’s jury verdict for a civil engineering firm in a negligent design claim involving New Hampshire's first private wastewater treatment facility, defeating an over $2 million damages claims by an adjoining commercial landowner.
  • Successfully defended founders, key employees and a publicly-traded distance learning software company in the defense of $1 billion trade secret, breach of fiduciary duty and contract claims in Chicago.
  • In bifurcated trial, won liability finding for plasma torch manufacturer on misappropriation of trade secrets claim against competitor and former employees.
  • Successfully represented a geotechnical engineer in a wrongful death action coupled with multiple property damage actions arising from the catastrophic collapse of an earthen dam.
  • Successfully represented a publicly traded HMO in the defense of a Sherman Act claim, alleging a small market attempt to monopolize through the use of exclusive physician contracts.
  • Defeated injunction request by disappointed buyer designed to prevent the sale of multi-million dollar publicly traded kitchen-ware company.
  • Defeated a preliminary injunction request and obtained positive resolution for the founders of a start-up electronic components firm in the defense of claims asserting the misappropriation of trade secrets, breach of fiduciary duty and breach of non-competition agreements.
  • Secured no damages ruling on over 99% of damages asserted in $1 million dollar fiduciary duty claim for shareholder of closely held corporation.


  • Admitted to practice in New Hampshire state and federal courts and before the First Circuit Court of Appeals. He is a member of the New Hampshire and American Bar Associations (ABA) and of the ABA’s Forum on the Construction Industry.
  • American Arbitration Association’s Panel of Construction Arbitrators.
  • Previously served on both the Advisory Committee to the United States District Court for the District of New Hampshire and the New Hampshire Bar Association’s Committee on Cooperation with the Courts.


  • Martindale Hubbell, “AV” rated
  • Chambers USA, Litigation: General Commercial
  • Best Lawyers in America®, Commercial Litigation
  • New England Super Lawyers®, Business Litigation