William O’Brien represents corporations and individuals in complex litigation involving corporate, commercial and securities-related matters. His practice focuses on pre-trial, trial and appellate work in federal and state courts.


Mr. O’Brien has participated in commercial arbitrations before the AAA and regulatory proceedings before the SEC and FINRA.

Mr. O’Brien has represented clients, both as plaintiffs and defendants, in actions involving a variety of federal and state statutes, including the Securities Exchange Act of 1934, the Securities Act of 1933, the Racketeering Influenced and Corrupt Organizations Act (RICO), the Delaware General Corporation Law and New York’s Business Corporation Law. He also has litigated a wide range of common law claims, including alleged breaches of contract, breaches of fiduciary duties, fraud, negligence and tortious interference.

Among others, Mr. O’Brien has represented:

  • Citigroup Global Markets, Inc., Goldman, Sachs & Co. and other financial institutions in opposing Securities Act claims arising from certain bond and equity offerings by Cobalt International Energy, Inc.;
  • Compuware Corporation and its board of directors in defending against breach of fiduciary duty claims arising from the company’s acquisition by Thoma Bravo, LLC;
  • The Royal Bank of Scotland Group plc and certain of its affiliates in defending against CDO-related lawsuits filed in both state and federal court;
  • Citigroup Inc., Discover Financial Services and Student Loan Corp. in defeating federal securities fraud claims arising from accounting-related disclosures;
  • UBS in defending against RMBS-related claims brought under the Securities Act of 1933 and the Blue Sky Laws of Virginia and the District of Columbia;
  • UniCredit S.p.A. in its defense of Madoff-related litigation, which was named among the top matters in the Litigation & Dispute Resolution category in the Financial Times’ 2013 “US Innovative Lawyers” report;
  • former officers and directors of Fremont General Corporation, a subprime lender, in defeating federal securities fraud claims stemming from the decline of the company’s residential mortgage lending business;
  • Citigroup Global Markets Inc., Goldman Sachs Credit Partners L.P., Deutsche Bank Trust Company Americas and Deutsche Bank Securities Inc. in a trial arising from a $2 billion financing facility for Solutia, Inc.;
  • an underwriting syndicate of financial institutions in multiple shareholder actions arising from the collapse of WorldCom, Inc., the global telecommunications provider; and
  • American Funds Distributors, Inc. in a seven-day enforcement hearing before the NASD (now FINRA).

Mr. O’Brien received his law degree from the University of Virginia School of Law, where he was a member of the editorial board and articles review board of the Virginia Law Review.



  • J.D., University of Virginia School of Law, 1996
  • B.A., Amherst College, 1993


  • New York

William J. O'Brien

Counsel, Complex Litigation and Trials