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William F. Sinnott

Partner at Hinckley Allen

William F. Sinnott's profile photo
LocationBostonMassachusetts, United States
Current rolePartnerHinckley Allen · since Jan 2021
Government service35yrsCity of Boston · U.S. Attorney’s Office · Norfolk District Attorney · U.S. Marine Corps

About

William F. Sinnott is a Partner in Hinckley Allen’s Litigation group. He brings to his current practice more than 39 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 biomedical 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, gangs, 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 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.

Roles

Jan 2021–Present
Current role

Partner

Hinckley Allen

Boston, Massachusetts

InvestigationsWhite Collar CrimeGovernmentLegal

Litigator focused on Government Investigations and White Collar Criminal Practice.

Jul 2014–Jan 2021
Former role

Partner

Barrett & Singal

Boston, Massachusetts

Civil LitigationInvestigationsWhite Collar CrimeGovernmentLegal
Jan 2014–Jul 2014
Former role

Associate Lecturer

Curry College

Milton, Massachusetts

ProfessorEducationEducation and Training

Instruct masters cohorts in Change Management in Criminal Justice Organizations and undergraduate students in Terrorism introductory course.

Jan 2006–Jan 2014
Former role

Corporation Counsel

City of Boston

(appointed)Boston, Massachusetts

AttorneyAttorney AdvisorLegal InvestigatorLegal

My staff and I represented the City, the Mayor, the City Council, and all City Departments in all litigation and other legal matters.

Sep 2001–Jun 2004
Former role

Partner

Sinnott Law Office

Boston, Massachusetts

Legal ServicesLegal InvestigatorLegal
Jun 1990–Jul 2001
Former role

Assistant United States Attorney

U.S. Attorney’s Office

(appointed)Massachusetts, District of

ResearchLegal AssistantInvestigationsLegal
Nov 1985–Nov 1989
Former role

Assistant District Attorney

Norfolk District Attorney

(appointed)Massachusetts

ResearchLegal AssistantLegal
Jul 1979–Jun 2009
Former role

Colonel

U.S. Marine Corps

Massachusetts, District of

National SecurityMilitary and Protective ServicesMilitary / Defense

Representative matters

Experience

August 2025

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.

Recognition

Honors

Best Lawyers in America® (2023-2026)

Best Lawyers

January 2025

- Commercial Litigation - Criminal Defense: White-Collar - Health Care Law

Top Lawyers (2024)

Boston Magazine

January 2024

Criminal Defense/White Collar

Super Lawyers (2023-2024)

Super Lawyers

Massachusetts | January 2023

Criminal Defense: White Collar (2023-2024)

Public Service Award

Rappaport Center

January 2014

Rappaport Center for Law and Public Service at Suffolk University, 2014 Public Service Award.

President’s Award for leadership in municipal law

Massachusetts Municipal Lawyers Association

January 2013

Honorary Degree: Doctor of Public Administration

Massachusetts Maritime Academy

January 2011

Honoris Causa, awarded in 2012 for service as Trustee, 2005-2011.

President’s Award for service in support of Diversity and Inclusion Committee’s Mentoring Program

Boston Bar Association

January 2011

Publications & speeches

What to know about Internal Investigations

Hinckley Allen Publications

November 2021

William F. Sinnott, Partner, shares why internal investigations are a smart business decision. In this media age of instant information, organizations are under constant scrutiny, and engaging in an internal investigation demonstrates transparency and a commitment to righting any wrongs uncovered. A company that does not proactively address allegations of misconduct, discrimination, or fraud appropriately can find itself out of business. Clients should consider the cost of not conducting an investigation and the potential fallout. Ultimately, the goal is for clients to come out of an investigation with a road map of how to do things better in the future, for both the organization and its employees.

Link

Prevent Your Work Site From Becoming a White Collar Crime Scene

Hinckley Allen Publications

August 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 dictate everything from contracts, payroll, hiring, and materials. If these regulations are not followed, the project can turn quickly into a white collar crime scene. “We find that oftentimes companies aren’t very familiar with these regulations, because they’re busy building some of the most sophisticated and complex projects in the Commonwealth and throughout the Northeast. They’re working with owners and designers and subcontractors and vendors, solving problems and getting projects built, efficiently, quickly, and on schedule,” says James J. Barriere, Co-Chair of Hinckley Allen’s Construction & Public Contracts Group. To stave off any potential civil or criminal liability, a robust compliance program is your best bet. Here’s what good programs have in common.

Link

As Boston Sees White Collar ‘Boom,’ Hinckley Allen Bulks Up

Law360

February 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.

Link

Mayor Menino and the Law as an Instrument of Change

Boston Bar Journal

September 2013

Link

Being “Comfortable with Chaos” and Leading by Example

Whitehead

August 2013

Link

Navigating Public Construction Minefields

CIM and UCANE — WEBINAR

May 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, sponsored by CIM and UCANE, will focus on recent legal developments and best practices to avoid and defend against law enforcement actions in the public construction industry.

Link