Sean F. O'Shea 

Partner – New York
T.+1 212 504 5700
200 Liberty Street
New York, NY 10281 V-CARD

Sean F. O’Shea, Chair of the Firm's Trial Practice Group, is a highly experienced, aggressive trial lawyer who focuses on complex business and white collar litigation. Sean has represented clients ranging from large corporations, to prominent private equity and hedge funds, to senior executives at major corporations. He has tried more than 87 cases to verdict, including federal and state jury and bench trials, arbitrations and administrative proceedings. He is particularly known as an expert cross-examiner whose cross-examinations have altered the course of trials. Sean has extensive experience with the RICO statute in civil cases having both successfully brought RICO actions and defended them on behalf of numerous corporate entities. 

Recently, Sean won a resounding trial victory in the Southern District of Texas. Faced with the total decimation of its direct case through witness cross-examination, McKinsey & Co, Inc was forced to withdraw its case before Sean offered any affirmative witnesses. Listen to the presiding judge after accepting McKinsey’s withdrawal and calling Sean O’Shea “one of the best trial lawyers I have ever seen.”

Fortune magazine profile of one of Sean’s many notable cases described him as "a top draw ... one of the toughest, most resourceful [of lawyers] ..." Sean was profiled in Lawdragon as one of the 500 top lawyers in the United States, as one of the 500 top litigators in the United States, and named a 2024 ‘Lawdragon Legend’. Conde Nast Portfolio has ranked him as one of the top 10 white collar criminal defense lawyers in New York City, noting his particular skill at avoiding indictment for his clients.

Sean is a former chief of the Business/Securities Fraud section of the United States Attorney's Office for the Eastern District of New York. During his decade-long tenure as a federal prosecutor, Sean tried more than 35 jury trials to verdict and appeared as lead appellate counsel for the Department of Justice in dozens of appeals to the United States Court of Appeals for the Second Circuit.

Sean has received numerous awards and commendations from the Department of Justice, the Federal Bureau of Investigation and other law enforcement agencies for his work in significant white collar crime matters. He has been a featured speaker on many occasions before federal law enforcement groups, including the Federal Bureau of Investigation and United States Postal Inspection Service.

Sean also served as an instructor in trial tactics and courtroom procedures classes at the Federal Bureau of Investigation Academy at Quantico, Virginia. Upon his departure from the United States Attorney's Office to return to private practice, FBI Director Louis Freeh wrote that Sean's "efforts as a prosecutor, as well as an investigator, were keys to the success of our White Collar Crime Program." He was also commended by Assistant Director of the FBI James Kallstrom for his work in a case against United States Aviation Underwriters. Mr. Kallstrom described Sean as being the "architect of the investigation and the prosecution presenting unique legal issues and facts [flowing out of the Pan Am 103 Lockerbie bombing investigation]."

Sean is committed to pro bono work and community service. He serves on the board of trustees of Cristo Rey School in Harlem and is past chair of the board of trustees of the Mashomack Nature Preserve, which is a Nature Conservancy property. He currently serves as an Advisor to the Indian River Land Trust in Vero Beach Florida. Sean is also an active supporter of the Red Cloud Indian School in Pine Ridge, South Dakota.

Sean received his J.D. from Northwestern University School of Law, where he was Notes and Comments Editor of the Northwestern University Law Review and a recipient of the Adlai Stevenson Award for writing the best appellate brief in the Julius Miner Moot Court Competition. He received his B.A. from the University of Illinois.

  • Winning a trial victory on behalf of Mar-Bow Value Partners (Jay Alix) against worldwide consulting giant McKinsey & Co, Inc. McKinsey was forced to withdraw their case after relentless, withering cross-examination of all of its witnesses in its direct case. Mar-Bow won its trial victory without presenting a single affirmative witness. The victory was the culmination of a multi-pronged, multi-jurisdictional effort to bring McKinsey into compliance with bankruptcy disclosure laws which it had been flouting for decades. Listen to Chief Judge David R. Jones' comments on Sean's trial and advocacy skills.
  • Winning a 2022 reversal in the Second Circuit Court of Appeals in Alix v. McKinsey Co., Inc., et al., a seminal RICO victory.
  • Obtaining a judgment in favor of client Kingsland Holdings Limited, which is serving as Independent Third Party in exercising remedies of United Airlines, Inc. associated with contracts effectuating loan obligations in excess of $500 million (loan secured by shares of Colombia-based Avianca Holdings SA). The judgment allows Kingsland to move toward a foreclosure sale on the Avianca Holdings SA shares securing the loan obligations.
  • Winning a total victory in the district court and on appeal to the Second Circuit in defense of a client charged in a civil RICO action with smuggling alcohol to avoid tens of millions of dollars in New York State excise taxes. He conducted a separate investigation of the plaintiff’s own business practices and uncovered actual smuggling by the plaintiff itself. He also filed a separate litigation against the plaintiff and recovered attorney’s fees against the plaintiff.
  • Winning a judgment exceeding $100 million for a private equity firm in a 10b-5 securities fraud and breach of contract litigation against Cendant Corporation in parallel actions in state and federal court flowing out of Cendant’s criminal accounting fraud.
  • In NML Capital v. Argentina, Sean was engaged on an emergency basis, and helped assemble a consortium of financial firms (including Brevan Howard, AllianceBernstein and MFS BlackRock) holding over $1 billion in exchange bonds issued by the Republic of Argentina. Acting under severe time constraints, he won a stay from the United States Court of Appeals for the Second Circuit preventing the enforcement of an injunction entered by a federal district court that would have interfered with the Republic's payments on over $24 billion in exchange bonds. The stay enabled the Republic's exchange bondholders to receive $3 billion in payments.
  • Persuading the Antitrust Division of the U.S. Department of Justice not to indict a senior executive at a multinational corporation, who had been identified as a target of the investigation of the optical disk drive industry.
  • Representing the founder and former president of AIG Global Real Estate in a successful action against AIG for in excess of $250 million in carried interest on all AIG real estate investments around the world.
  • Representing the co-founder of a large internet gaming company targeted for prosecution for violation of various state and federal gaming statutes and money laundering. Several years into the investigation, after replacing prior counsel who had recommended a guilty plea, Sean designed and implemented a defense strategy that resulted in the government ultimately declining to indict his client. The client's co-founder, represented by other counsel, pled guilty and agreed to pay a $300 million criminal forfeiture.
  • Prevailing at trial in seeking return of funds seized by the IRS, which claimed the client company had structured its bank deposits to evade taxes. After waiving jury trial, Sean employed a technical tax defense, aggressively cross-examining government witnesses and agents. After trial, the court ordered the forfeited funds returned and the client's legal fees reimbursed.
  • Obtaining a multimillion dollar award for an executive who conceived and introduced the Refco/Thomas H. Lee leveraged buyout. The trial was conducted almost entirely by cross-examination of adverse witnesses who denied the involvement of his client. Each successive witness was discredited by relentless cross-examination.
  • Representing a prominent private equity firm as the plaintiff in a securities fraud case venued in the United States District Court for the Southern District of New York. After the original complaint was dismissed, Sean replaced the client's existing counsel, formulated new causes of action, and filed an amended action. The revamped complaint survived the defendants' motions to dismiss, and Sean thereafter engineered a favorable eight-figure settlement prior to any deposition discovery.
  • Successfully representing an insurance industry executive threatened with indictment in a high profile investigation conducted by the New York Attorney General. Sean replaced prior counsel and persuaded the AG's office not to indict.


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Sean F. O'Shea 


  • U.S. Supreme Court
  • U.S. Court of Appeals, 2nd Circuit
  • U.S. Court of Appeals, 6th Circuit
  • U.S. Court of Appeals, 7th Circuit
  • U.S. Court of Appeals, 9th Circuit
  • U.S. District Court, Southern District of New York
  • U.S. District Court, Eastern District of New York
  • U.S. District Court, Western District of Michigan
  • U.S. District Court, Northern District of Illinois
  • U.S. Tax Court
  • New York
  • Illinois


  • Northwestern Pritzker School of Law
  • University of Illinois