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Sean P. Tonolli

Sean P. Tonolli


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Cahill Gordon & Reindel LLP
1990 K Street, N.W.
Suite 950
Washington, D.C. 20006

32 Old Slip
New York, NY 10005



  • Stanford Law School, J.D., 2005, with Distinction
  • The College of William and Mary, B.A., 2002, magna cum laude, James Monroe Scholar

Clerkships/Government Service

  • Hon. J. Frederick Motz, U.S. District Court, District of Maryland, 2005-2006
  • Assistant U.S. Attorney for the District of Columbia, 2006-2010
  • Assistant U.S. Attorney for the Eastern District of Virginia, 2010-2014


  • District of Columbia
  • New York
  • Virginia

A partner in Cahill’s litigation practice group, Sean is a former federal prosecutor with extensive investigative and first-chair trial experience. His practice focuses on white-collar criminal defense, government enforcement, internal investigations, compliance assessments and diligence, and securities and commercial litigation. Companies, boards and individuals rely on him to handle their most sensitive and high-stakes matters, whether internal, government-facing or in the courtroom.

Sean represents clients in a variety of industries, from banking and financial services to biotech to transportation to non-profit. Their footprints are global and the legal issues he handles for them are varied, including the Foreign Corrupt Practices Act, the Bank Secrecy Act and anti-money laundering laws, economic sanctions, insider trading, accounting and securities fraud, environmental- and safety-related laws, and the First Amendment, defamation and libel. Sean also counsels clients on mission-critical diligence, be it vetting of potential acquisition targets and new business partners, or assessing and enhancing compliance programs and the policies, procedures and training modules necessary to ensure effective implementation.

In 2019, Sean was named a Rising Star by both the National Law Journal and Law360 for his white collar defense and securities litigation work. Sean was also named to Benchmark Litigation’s 40 & Under Hot List in 2020.

While many of Sean’s matters are not public, some of his recent representations include:

  • A former KPMG audit partner in a criminal prosecution in the Southern District of New York;
  • An individual in the investigation by Special Counsel Robert Mueller;
  • An executive of an automobile manufacturer in investigations by U.S. and German authorities concerning diesel emissions;
  • An executive of an international energy corporation in a Congressional investigation;
  • Credit Suisse in various securities-related regulatory matters, to include FCPA enforcement actions by the DOJ and SEC;
  • Princess Cruise Lines in a cross-border environmental enforcement action by DOJ;
  • A leading automobile manufacturer in an SEC enforcement action;
  • The CEO and Chairman of Manning Broadcasting in a shareholder derivative suit;
  • An activist hedge fund and its Chief Investment Officer in a defamation suit;
  • The DOJ-appointed monitor of Toyota throughout a three-year monitorship focusing on vehicle safety and the accuracy of Toyota’s public statements; and
  • A national homebuilder in DOJ and SEC enforcement actions for accounting fraud.

Prior to joining Cahill, Sean served for eight years as an Assistant U.S. Attorney in the Eastern District of Virginia and the District of Columbia. He led complex prosecutions of domestic and international criminal activity involving a wide array of offenses, including money laundering, wire fraud, obstruction of justice, homicide and conspiracy. He first-chaired over 40 trials and conducted over 100 grand jury investigations. For his skill in the courtroom handling a multi-month trial centered on the murder of a government witness, Sean received the John Marshall Award – Outstanding Legal Achievement for Trial of Litigation, the highest award given to DOJ attorneys. He also received four Special Achievement Awards.

Sean graduated magna cum laude from the College of William & Mary and with distinction from Stanford Law School, where he served as editor of the Stanford Law Review and the Stanford Journal of International Law. He clerked for the Honorable J. Frederick Motz of the U.S. District Court for the District of Maryland. He is a member of the bars of D.C., New York, and Virginia.