Sean Tonolli Returns to Cahill as Litigation Partner

January 5, 2026

Cahill today announced that Sean Tonolli has returned to the firm as a litigation partner in our growing Washington, D.C. office. Sean advises companies, boards, and executives in white collar defense and investigations, securities and business litigation, and congressional investigations.

Sean rejoins Cahill after more than four years of service in the federal government, including most recently as the second-in-command (Acting Principal Deputy Chief) of the DOJ Criminal Division’s Fraud Section.

“We could not be more pleased that Sean is returning to Cahill, after his years of leadership within the Department of Justice’s Criminal Division,” said Herb Washer, Chair of Cahill’s Executive Committee. “Clients greatly valued Sean’s exceptional guidance during his original tenure with Cahill. Now he returns to us with deep insight, perspective, and relationships that will benefit our clients immeasurably.”

During his Fraud Section tenure, Sean supervised over 200 prosecutors handling the department’s most sophisticated white-collar matters, including securities and cryptocurrency fraud; health care fraud; money laundering; government program, procurement, and trade fraud; and violations of the Foreign Corrupt Practices Act and the Food, Drug, and Cosmetic Act. He also helped to oversee corporate resolutions collectively involving billions of dollars; develop the Criminal Division’s corporate enforcement and whistleblower policies; and guide the integration of the Consumer Protection Branch and its health and safety portfolio into the Section. He previously served as Chief of the Section’s Litigation Unit, overseeing dozens of trials across the country and personally handling some of the Section’s most significant and sensitive matters.

Sean first joined Cahill in 2014, rising to partner before departing in 2021 for his second stint in government service. From 2006 to 2014, Sean served as a decorated federal prosecutor in the Eastern District of Virginia and the District of Columbia.