Attorneys & Professionals

Sean Tonolli is a former senior leader of the DOJ’s Fraud Section and congressional counsel who focuses on government and internal investigations; business and securities litigation; and compliance-advisory matters.

Sean draws on more than twenty years of litigation experience in private practice and public service—including dozens of trials—to guide his clients through high-stakes investigations and disputes. He has represented clients in matters involving, among others, the DOJ, SEC, FinCEN, FINRA, congressional committees, state attorneys general, and foreign regulators like the U.K.’s Serious Frauds Office and Japan’s Financial Services Agency.

Sean returned to Cahill in 2025 having most recently served as the Fraud Section’s second-in-command (Acting Principal Deputy Chief). He supervised over 200 prosecutors handling DOJ’s most sophisticated white-collar matters, including securities and cryptocurrency fraud; health care fraud; money laundering; government program, procurement, and trade fraud; the Foreign Corrupt Practices Act; and the Food, Drug, and Cosmetic Act. He helped develop the Criminal Division’s corporate enforcement and whistleblower policies, and oversaw corporate resolutions totaling billions of dollars. He also previously served as Chief of the Litigation Unit, overseeing dozens of trials across the country and personally handling some of the Section’s most significant and sensitive matters.

Before his Fraud Section tenure, Sean served as a senior investigative counsel to a congressional select committee. He and his team deposed hundreds of witnesses, including former Executive Branch officials, and he led the preparation for nationally televised public hearings.

Sean first joined Cahill in 2014 following eight years serving as a federal prosecutor in the Eastern District of Virginia and the District of Columbia. He received numerous awards for his investigative and trial work, including the Attorney General’s John Marshall Award—the highest award for DOJ attorneys—for a multi-month, six-defendant jury trial.

Representation of an automotive executive in parallel investigations by the DOJ Fraud Section and foreign authorities related to emissions.
Representation of a founder in a wire-fraud prosecution in S.D.N.Y. and parallel SEC enforcement action.
Representation of a Big Four audit partner in a wire fraud prosecution in S.D.N.Y. and parallel SEC enforcement action.
Representation of a senior oil-and-gas executive in a Congressional investigation.
Representation of Credit Suisse in various domestic and cross-border securities- and commodities-related regulatory matters.
Representation of an auto manufacturer in an SEC securities investigation.
Representation of an oil-and-gas company in internal and government-facing accounting investigations.
Representation of an asset manager and its portfolio companies in connection with internal compliance investigations, M&A diligence, and other regulatory matters, including FCPA and trade sanctions compliance.
Member of the monitorship team that oversaw Toyota in connection with a Deferred Prosecution Agreement entered into with S.D.N.Y.

Sean P. Tonolli