Partner
Hinckley Allen
Boston, Massachusetts
Litigator focused on Government Investigations and White Collar Criminal Practice.
Partner at Hinckley Allen

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.
Hinckley Allen
Boston, Massachusetts
Litigator focused on Government Investigations and White Collar Criminal Practice.
Barrett & Singal
Boston, Massachusetts
Curry College
Milton, Massachusetts
Instruct masters cohorts in Change Management in Criminal Justice Organizations and undergraduate students in Terrorism introductory course.
City of Boston
(appointed)Boston, Massachusetts
My staff and I represented the City, the Mayor, the City Council, and all City Departments in all litigation and other legal matters.
Sinnott Law Office
Boston, Massachusetts
U.S. Attorney’s Office
(appointed)Massachusetts, District of
Norfolk District Attorney
(appointed)Massachusetts
U.S. Marine Corps
Massachusetts, District of
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.
Best Lawyers
January 2025
- Commercial Litigation - Criminal Defense: White-Collar - Health Care Law
Boston Magazine
January 2024
Criminal Defense/White Collar
Super Lawyers
Massachusetts | January 2023
Criminal Defense: White Collar (2023-2024)
Rappaport Center
January 2014
Rappaport Center for Law and Public Service at Suffolk University, 2014 Public Service Award.
Massachusetts Municipal Lawyers Association
January 2013
Massachusetts Maritime Academy
January 2011
Honoris Causa, awarded in 2012 for service as Trustee, 2005-2011.
Boston Bar Association
January 2011
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.
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.
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.
Boston Bar Journal
September 2013
LinkWhitehead
August 2013
LinkCIM 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.