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Mayer Brown has continued the expansion of its regulatory, investigations and enforcement capabilities with the arrival of federal prosecutor Sean McDonnell, who rejoins the firm as a partner in the global Litigation & Dispute Resolution practice in Washington DC. Previously, Mr. McDonnell was an Assistant United States Attorney (AUSA) in the US Attorney’s Office for the Eastern District of Pennsylvania.

“Sean is widely respected as an extremely talented trial lawyer with extensive civil litigation, government enforcement and investigations experience; we are fortunate to welcome him back to Mayer Brown,” said Richard Spehr, the leader of Mayer Brown’s global Litigation & Dispute Resolution practice. “Sean will work closely with our expanding bench of former federal prosecutors and high-ranking government officials to help clients with their most challenging bet-the-company matters. His recent work coordinating investigative agencies and districts on COVID-19-related government fraud cases—where significant government activity is expected—deepens the firm’s capabilities in this space.”

During his tenure as a federal prosecutor, Mr. McDonnell first-chaired several jury trials to verdict and oversaw large-scale investigations, including complex wiretap and forensic financial investigations. He prosecuted a variety of cases involving, among other things, tax fraud, wire fraud, insurance fraud, bank fraud and public corruption. Most recently, he served as the US Attorney’s coordinator for COVID-19-related government fraud cases, including all cases that involved the CARES Act and Paycheck Protection Program and Economic Injury Disaster Loans fraud investigations.

“Coming back to Mayer Brown is like coming home for me,” said Mr. McDonnell. “I am excited to rejoin the firm’s collegial and exceptionally talented litigation team to help clients navigate the impending uptick in federal enforcement and investigative activities.”

Mr. McDonnell is the fifth former federal prosecutor to join Mayer Brown in recent years. Previously, Gina Parlovecchio joined from the Eastern District of New York and Daniel Stein and Glen Kopp joined from the Southern District of New York. The firm also welcomed former prosecutors Michael Levy and Jason Linder to its Washington DC and Los Angeles/DC offices, respectively.

Before his AUSA stint, Mr. McDonnell was a litigator in Mayer Brown’s Chicago and Washington DC offices, where he represented corporate clients in white collar investigations and various civil litigation matters, including antitrust and securities cases. Earlier in his career, Mr. McDonnell clerked for the Honorable Rebecca Pallmeyer of the US District Court for Chicago and served as an appellate law clerk for the Cook County State’s Attorney’s Office. He regularly teaches classes on managing legal risk at the University of Pennsylvania’s Wharton Business School, including a recent “Crash Course on Internal Investigations” seminar for Wharton’s executive education program.

As Raj De, the managing partner of Mayer Brown’s Washington DC office, observes, “Sean has an impressive combination of civil litigation and law enforcement experience. His deep understanding of how to navigate complex government investigations make him a tremendous asset to the firm’s clients and expanding Washington office, which has welcomed several leading former government officials over the past year.”