Sean R. O'Brien has successfully represented hedge funds, private equity firms, corporations, financial institutions, investors, small businesses and individuals in a range of civil, regulatory, and criminal proceedings. Mr. O'Brien's practice principally involves disputes arising out of complex financial transactions, shareholder and partnership disputes, and employment disputes. Mr. O'Brien has significant experience in representing hedge funds, as well as their principals and employees, in such matters.
Mr. O'Brien clerked on the United States Court of Appeals for the Second Circuit, and then began his career at Sullivan & Cromwell LLP, where for one year he litigated his own prisoner civil rights cases as the firm's Pro Bono Fellow. Mr. O'Brien later practiced at Sullivan & Cromwell in the areas of securities and antitrust litigation, and was a member of the trial team in the defense of the Department of Justice's landmark case against Microsoft Corporation. Between 2003 and the founding of O'Brien LLP, Mr. O'Brien was a partner at a litigation boutique headed by Stanley S. Arkin, one of the nation's foremost white-collar criminal defense attorneys. At that firm, Mr. O'Brien successfully resolved complex litigation throughout the country at the trial and appellate level.
Mr. O'Brien is a contributing author to the Hedge Fund Law Report.
Notable representations include:
- Represented a hedge fund in a litigation brought against a former employee who had disclosed confidential information of the firm and violated a non-disparagement agreement, obtaining an arbitral award in favor of the firm and substantial damages.
- Represented a hedge fund manager as co-lead counsel in jury trial pursuing claims of fraud and breach of fiduciary duty against a well-known public REIT, obtaining a verdict of $12.7 million, including punitive damages, and dismissal of all claims asserted against the client.
- Represented a multibillion-dollar hedge fund in a three-week jury trial, obtaining dismissal of all damage claims brought against the fund, and $3 million in damages and attorneys' fees award in favor of the fund.
- Represented a hedge fund in insider trading investigation and related lawsuit brought by SEC, obtaining dismissal of all claims.
- Represented a hedge fund in action commenced by counterparty seeking $350 million based upon alleged misuse of confidential information, obtaining dismissal of all claims prior to commencement of discovery.
- Represented a hedge fund in criminal investigation arising out of misappropriation of trade secrets.
- Represented an individual in United States v. Stein, et al., the largest tax-shelter prosecution ever brought by the Department of Justice, obtaining dismissal of all claims based upon governmental interference with employer's obligation to advance attorneys' fees.
- Represented the sole manager of a $1.3 billion hedge fund in dispute and action brought against him arising out of dissolution of fund, obtaining dismissal of all claims.
- Represented a leading investment bank in action alleging breach of contract and fraud in connection with private securities offering, obtaining dismissal of all claims.
- Represented a top-five law firm and partner defending against multimillion-dollar claims arising out of a merger transaction, obtaining dismissal of all claims.
- Represented Microsoft Corporation as member of trial team in United States v. Microsoft Corporation, an antitrust enforcement action brought by the Department of Justice.
