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Sinnott, Bill

William F. Sinnott


William F. Sinnott is a Partner in Hinckley Allen’s Litigation group. He brings to his current practice more than thirty-five years of legal experience as a successful civil and white collar criminal practitioner, as a line and supervisory municipal, state, and federal government attorney, 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, attorneys, judicial and government officers and litigates on their behalf in numerous courts, including United States District Court, the Court of Federal Claims, and the District and Superior Courts of Massachusetts.

Bill previously served for 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.


  • Served as Lead Counsel to a major Massachusetts carrier in an action against the federal government and secured recovery of almost $30 million.
  • Defended a Boston heath care institution against discrimination claims and obtained near-complete vindication by a Superior Court jury following a two week trial.
  • Served as lead counsel to a Boston construction company in a partnership dispute and tried the case to a successful conclusion following an eight-day bench trial in the Business Litigation Session.
  • Litigated to dismissal an action against a Massachusetts municipal official alleging defamation and civil rights violations.
  • Assigned by the United States District Court as Counsel to a Special Master charged with conducting a three-year investigation of an MDL fee award resulting in a 400-page Report & Recommendations.
  • 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.
  • 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.


Work Experience

  • Hinckley Allen
    • Partner
  • Barrett & Singal
    • Partner
  • City of Boston, Massachusetts
    • Corporation Counsel (2006-2014)
  • United States Attorney's Office (Boston)
    • Assistant United States Attorney (1990-2001)
  • Norfolk County, Massachusetts
    • Assistant District Attorney (1985-1989)

Honors & Awards

  • 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

Charitable & Civic Involvement

  • Trustee, Boston Latin School Association (2019-Present)
  • Member, appointed by the Governor, of the Veterans Long Term Care Commission, tasked with recommending legislation to improve health care and housing options for veterans (2014-2017)
  • Appointed by Governor as Trustee, Massachusetts Maritime Academy and served as Chairman of Governance Committee (2005-2011)
  • Life Member, Marine Corps Reserve Association

Professional Affiliations

  • Boston Bar Association
    • Original member of the Diversity Task Force (2009)
    • Elected Council Member (2009-2012)
    • Founding Co-Chair of BBA's Committee on Legal Services for Veterans, Military Personnel and Families (2009-2010)
  • Executive Council Member, Boston Lawyers Group (2006-2014)
    • An organization committed to diversifying the legal profession in Massachusetts
  • Keynote Speaker, Massachusetts Bar Association's In House Counsel Conference (2011) and Massachusetts Continuing Legal Education In House Training Seminar (2014)

Bar Memberships

  • Commonwealth of Massachusetts
  • United States District Court for the District of Massachusetts
  • United States Court of Appeals for the First Circuit
  • United States Court of Federal Claims

Speaking Engagements

  • 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

News & Insight


Prevent Your Work Site From Becoming a White Collar Crime Scene

August 17, 2021

Public construction projects are the backbone of any community, paid for and overseen by the state or local government.  They provide infrastructure and jobs, boosting local economies. These kinds of projects are also subject to a slew of regulations that…


As Boston Sees White Collar 'Boom,' Hinckley Allen Bulks Up

February 16, 2021

High-profile cases in Boston are growing and Hinckley Allen is expanding the white collar practice to meet client need. Partners Michelle Peirce, Bruce Singal and Laura Angelini sat with Law360 to discuss.

Firm News

Hinckley Allen Expands Litigation Group with Eight Lateral Hires from Barrett & Singal

January 5, 2021

Hinckley Allen today announced that eight trial lawyers from Barrett & Singal have joined the Firm, including Co-Chairs of Barrett & Singal’s Litigation group, Co-Chairs of its Research Misconduct group, and its General Counsel. All eight new hir…


Past Event

WEBINAR: Navigating Public Construction Minefields

May 13, 2021

Hinckley Allen construction, environmental and government enforcement & white collar defense attorneys have teamed up to address important developments and legal issues relating to government investigations of public contractors.  This webinar, sponso…