One Beacon Street
Suite 1320
Boston, MA 02108

T 617.720.5090
F 617.720.5092


One Richmond Sq.
Suite 165W
Providence, RI 02906
T 401.454.0400
F 401.454.0404

William Sinnott

Practice Area:Litigation

William Sinnott is a partner in Barrett & Singal’s Litigation practice. He has almost thirty years of legal experience as a line and supervisory municipal, state, and federal government attorney, as a successful private practitioner, and as a teacher and leader in the legal community. He advises and advocates for a diverse range of individuals and organizations including healthcare and pharmaceutical institutions and employees, contractors, universities, and government officers.

Bill most recently served eight years as the Corporation Counsel of the City of Boston where he was head of the Law Department. In that capacity, he and his staff represented the City, the Mayor, the City Council, and all City Departments in all litigation and other legal matters. His law experience before that was principally as a prosecutor, including eleven years as an Assistant U.S. Attorney in Boston, during a period of which he served as Chief of the New England Organized Crime Drug Enforcement Task Force. As an Assistant U.S. Attorney, Bill tried dozens of cases in federal court involving narcotics, gang, organized crime, weapons, and financial crime violations. While serving as a state prosecutor, Bill represented the Commonwealth in hundreds of matters before appellate and trial courts. As a private practitioner, Bill secured judgments totaling millions of dollars in several Superior Court trials.

Bill has also had a distinguished military career spanning 32 years with the United States Marine Corps, from which he retired as a Colonel. This included active duty tours in Bosnia and Iraq, among other assignments.

Awards & Recognitions

Rappaport Center for Law and Public Service at Suffolk University, 2014 Public Service Award
Massachusetts Municipal Lawyers Association, 2013 President’s Award for leadership in municipal law
Honorary Degree: Massachusetts Maritime Academy, Doctor of Public Administration, Honoris Causa, awarded in 2012 for service as Trustee, 2005-2011
Boston Bar Association, President’s Award for service in support of Diversity and Inclusion Committee’s Mentoring Program

Professional background

Corporation Counsel, City of Boston, Massachusetts, 2006–2014
Assistant United States Attorney, United States Attorney’s Office, Boston, Massachusetts, 1990-2001
Assistant District Attorney, Norfolk County, Massachusetts, 1985-1989


Suffolk University Law School, Boston, Massachusetts, J.D., 1985
College of the Holy Cross, Worcester, Massachusetts, B.A. in Classics, 1979
Boston Latin School, Boston, Massachusetts, High School Degree, 1975

Court / Bar Admissions

United States Court of Appeals for the First Circuit
U.S. District Court for the District of Massachusetts

Service areas

Healthcare litigation; Pharma/Healthcare fraud; Scientific misconduct; Defense procurement fraud; Professional licensing and disciplinary; Public corruption; Export violations; Municipal Law and Elections; National Security Law; Civil Rights Defense


Healthcare providers; Hospitals; Biomedical/Life sciences; Universities; Exporters; Government Officials and Candidates; Government contractors; Law Enforcement; Medical devices; Pharmaceutical; Pharmacies/Pharmacists; Physicians; Professional services; Scientists; Transportation

Presentations & Publications

Keynote Speaker, MCLE Twelfth Annual Municipal Law Conference (2014); Massachusetts Bar Association’s In House Counsel Conference (2011); Boston Municipal Research Bureau Monthly Meeting (2006); and numerous other academic, bar advocacy and community group meetings
Mayor Menino and the Law as an Instrument of Change, September, 2013
Occupy Boston: Lessons Learned Massachusetts Municipal Law Quarterly, Summer 2012 (Sinnott)
Sinnott: Being “Comfortable with Chaos” and Leading by Example, August, 2013

Civic & charitable activities

Founding Co-Chair of Boston Bar Association’s Committee on Legal Services for Veterans, Military Personnel and Families (2009-2010).
Elected Council Member, Boston Bar Association (2009-2012)
Original member of BBA’s Diversity Task Force (2009)
Executive Council Member, Boston Lawyers Group (2006-2014)
Appointed by Governor as Trustee, Massachusetts Maritime Academy and served as Chairman of Governance Committee (2005-2011)
Elected Board Member, Civil Affairs Association of the United States (1998-present)

off the record

An avid runner and member of the legendary L Street Running Club, Bill regularly runs in road races, including three marathons per year. “I love the community of runners and the energy they exude. We compete, not with each other, but with our own expectations.”

representative matters

  • Advised City officials on all legal facets of Occupy Boston and led the City’s successful litigation in superior court resulting in a peaceful and legally-defensible conclusion to the encampment in Dewey Square
  • Advised City officials, including the Mayor and City Councilors, on Voting Rights Act and other legal concerns surrounding the re-configuration of Boston electoral districts, leading to a widely-accepted and commended redistricting plan that was enacted without legal challenge
  • Oversaw and coordinated many months of investigation by federal law enforcement agencies and prosecuted numerous defendants in multiple trials and pleas in federal court resulting in the dismantling of a violent urban drug-trafficking gang
  • Coordinated with United States and European law enforcement and diplomatic offices to investigate, arrest and extradite members of an international heroin-smuggling ring resulting in prosecution in federal court and lengthy prison sentences
  • Prepared and litigated in superior court on behalf of a young man rear-ended by a commercial vehicle and suffering from a debilitating pain syndrome, resulting in a multi-million dollar jury award



bio pdf


This website presents general information about Barrett & Singal and is not intended as legal advice nor should you consider it as such. You should not act upon this information without seeking professional counsel.

Please note that contacting Barrett & Singal by email, telephone or facsimile will not establish an attorney-client relationship, obligate us to act as your attorney or impose an obligation on either the law firm or the receiving lawyer to keep the transmitted information confidential. Completion of Barrett & Singal’s new client intake protocol, including without limitation the firm’s conflicts checking process and an engagement letter, is necessary to establish an attorney-client relationship. Absent a current attorney-client relationship with Barrett & Singal, any information or documents communicated or transmitted by you to Barrett & Singal will not be treated as confidential, secret or protected in any way. If you are not a current client of Barrett & Singal, please do not send any confidential information to us through this web site or otherwise concerning any potential or actual legal matter you have. Before providing any confidential information to us, you must obtain permission to do so from one of the firm’s lawyers. By clicking "Accept," you acknowledge that we have no obligation to maintain the confidentiality of any information you submit to us unless we already represent you or unless we have agreed to receive limited confidential material/information from you as a prospective client.

If you would like to discuss becoming a client, please contact one of our attorneys to arrange for a meeting or telephone conference. If you wish to disclose confidential information to a lawyer in the firm before an attorney-client relationship is established, the protections that the law firm will provide to such information from a prospective client should be discussed with the firm attorney before such information is submitted. Thank you for your interest in Barrett & Singal.