Sean R. O'Brien



Managing Partner
  Location: New York, New York
  Phone: 212-729-9243 |  Fax: 646-205-3071
  Email: sobrien@obrienllp.com


Sean R. O'Brien has successfully represented hedge funds, private equity firms, commercial banks, investment banks, investors, small businesses and individuals in a wide-range of disputes and 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 and trade secret disputes. Mr. O'Brien has significant experience in representing hedge funds and other private investment firms as well as their principals and employees in such matters.

Following law school 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. Prior to 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 levels.

Notable Representations

    • Represented an investment bank in an action to recover a transaction fee, prevailing in all respects after multi-day arbitration. 
    • Represented an individual in an insider trading investigation commenced by the Department of Justice, resolving the matter with no charges being brought. 
    • Represented a private investment firm and obtained the complete dismissal, following an arbitral hearing, of multi-million dollar claims based upon an alleged breach of a capital-raising agreement and related fraud. 
    • Represented a hedge fund in dispute with former employees and obtained dismissal of multi-million dollar claims for performance-based compensation. 
    • Represented publicly-traded commercial bank as defendant in action involving alleged multi-million dollar fraud and fraudulent transfers, obtaining dismissal of all claims. 
    • 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 in an investigation and civil action by the Securities & Exchange Commission involving alleged insider trading, obtaining the dismissal of all claims.
  • 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 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 Microsoft Corporation as member of trial team in United States v. Microsoft Corporation, an antitrust enforcement action brought by the Department of Justice.

Education

  • New York University School of Law, New York, New York
    •   J.D. Magna Cum Laude - 1994
    •   Honors: Order of the Coif
    •   Senior Note and Comment Editor, Law Review
  • Harvard College, Cambridge, Massachusetts
    •   A.B. Cum Laude - 1989

Published Works

    “Defend Trade Secrets Act Provides Hedge Fund Managers With Protections for Proprietary Trading Technology and Other Trade Secrets,” The Hedge Fund Law Report, Vol. 9, No. 25 (June 23, 2016), by Sean R. O’Brien and A.J. Monaco.

    "How Can Hedge Fund Managers Protect Themselves Against Trade Secret Claims?,” The Hedge Fund Law Report, Vol. 7, No. 19 (May 16, 2014), by Sean R. O’Brien, Sara A Welch and A.J. Monaco.

    “Hedge Fund Incentive Compensation Not Subject to Wage Claim Under New York Labor Law,” The Hedge Fund Law Report, Vol. 7, No. 14 (April 11, 2014), by Sean R. O’Brien and Sara A. Welch.

    “Recent Developments Affecting the Protection of Trade Secrets by Hedge Fund Managers,” The Hedge Fund Law Report, Vol. 6, No. 41 (Oct. 24, 2013), by Sean R. O'Brien and Sara A. Welch.

    "Can Hedge Fund Managers Contract Out Of Default Fiduciary Duties When Drafting Delaware Hedge Fund and Management Company Documents?," The Hedge Fund Law Report, Vol. 6, No. 14 (Apr. 4, 2013), by Sean R. O'Brien and Sara A. Welch.

    "Computer Crime in New York Federal and State Courts," The New York Law Journal (Nov. 1, 2012), by Sean R. O'Brien and Sara A. Welch.

    "Protecting Hedge Funds' Trade Secrets: What A Difference A Year Makes," The Hedge Fund Law Report, Vol. 5, No. 16 (Apr. 19, 2012), by Sean R. O'Brien and Sara A. Welch.

    "Portability and Protection of Hedge Fund Investment Track Records," Hedge Fund Law Report, Vol. 4, No. 40 (Nov. 10, 2011), by Sean R. O'Brien, Sara A. Welch and Joel A. Blanchet.

    "Protecting Hedge Funds' Trade Secrets: The Federal Government's Enforcement of Criminal Laws Protecting Proprietary Trading Strategies," The Hedge Fund Law Report, Vol. 3, No. 48 (Dec. 10, 2010), by Sean R. O'Brien and Sara A. Welch.

    "The Computer Fraud and Abuse Act, A New Prosecutorial Weapon?," Business Crime Bulletin July 2010 by Stanley S. Arkin, Sean O'Brien and David Pohl.

    "Effective Use of Private Investigators," New York Law Journal (Dec. 26, 2007), by Stanley S. Arkin and Sean R. O'Brien.


Bar Admissions

  • New York, 1995
  • U.S. District Court Southern District of New York, 1995
  • U.S. District Court Eastern District of New York, 1996
  • U.S. Court of Appeals 2nd Circuit, 2008
  • U.S. Court of Appeals 8th Circuit, 2003
  • U.S. Court of Appeals 9th Circuit, 2003
  • U.S. Court of Appeals 10th Circuit, 2008

Professional Associations and Memberships

  • City Bar Association, Federal Courts Committee, 2010 - 2012
  • Federal Bar Council, Program Committee, 2011 - Present