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Sean P. McDonnell

Sean P. McDonnell

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Guide to Anti-Corruption Laws in Major Jurisdictions


Securities Investigations: Internal, Civil and Criminal

Securities Investigations: Internal, Civil and Criminal

Sean P. McDonnell is an associate in Mayer Brown’s Washington DC office and a member of the Litigation & Dispute Resolution practice. He has experience in a wide variety of civil and criminal matters, ranging from contractual disputes to complex regulatory enforcement actions. He has handled both jury and bench trials in state and federal court, including a high-profile civil fraud case in which Sean represented a large financial institution seeking to recover over $40 million in fraudulently-borrowed funds.  Sean has also handled criminal sentencing hearings in both state and federal court, and has represented testifying witnesses in federal grand jury proceedings. 

Sean also has significant investigation experience, having assisted in the conduct of internal investigations related to SEC and Department of Justice activity on behalf of corporate clients. He regularly advises clients regarding regulatory and policy matters, including compliance with the Foreign Corrupt Practices Act (FCPA) and other facets of the securities laws.  He has written about the FCPA and the extraterritorial application of US law more generally.

Sean was also a member of the litigation team that successfully represented then-candidate Rahm Emanuel against challenges to his candidacy for Mayor of the City of Chicago, culminating in a unanimous favorable decision in the Illinois Supreme Court.  He has advised other political campaigns and interest groups on regulatory issues related to election law and voting rights. 

Prior to joining Mayer Brown, Sean served as law clerk to the Honorable Rebecca Pallmeyer of the United States District Court for the Northern District of Illinois. He graduated magna cum laude from Harvard Law School in 2009, where he was the Senior Policy Editor of the Harvard Law and Policy Review. Sean has been a guest lecturer at Northwestern University School of Law on topics relating to the nexus between law and politics. He is a former board member of his local township committee of the Democratic Party, and he is active in the American Constitution Society and the Harvard Club of Washington.

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