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Gregg Mashberg is co-head of the Securities Litigation Group and a former Chair of the Litigation Department. He has a broad-based practice and experience before numerous judicial and administrative forums.

Gregg has a particular focus on securities litigation, defending public companies and their directors and officers in class actions, SEC investigations and enforcement actions. Gregg also has broad experience in defending directors and officers in shareholder derivative actions and direct breach of fiduciary duty suits under state law. As part of his securities litigation practice, Gregg is outside litigation counsel for The Depository Trust & Clearing Corporation and its subsidiaries, the nation's principal securities settlement and depository institutions. He has litigated in trial and appellate courts around the country, successfully defending against claims challenging the securities clearing and settlement system.

In addition, Gregg has been active in litigation concerning various high-tech industries. He has substantial experience litigating disputes relating to telecommunications services and automated systems for processing securities transactions.

Gregg also has substantial litigation experience involving core aspects of Proskauer’s litigation practice, including general commercial disputes, antitrust, bankruptcy, entertainment, sports, First Amendment and trade secrets. He recently won summary judgment in a commercial dispute on behalf of a major British company, dismissing a complaint seeking $100 million in damages. Gregg is an experienced courtroom lawyer; for example, he won a $3 million federal jury verdict in a stockholders’ derivative action in a case involving the closing of a Wall Street brokerage house.

Following law school, Gregg spent five years in the New York City Corporation Counsel's Office, becoming an Assistant Chief of the General Litigation Division. In that position, Gregg was lead counsel for the City in major institutional change class actions. He also represented the City in litigation concerning significant public policy disputes.

Gregg has maintained his interest in public law, most recently serving as lead counsel to St. Vincent's Catholic Medical Center in defending against an Article 78 proceeding that challenged the NYC Landmarks Preservation Commission's decision to permit St. Vincent's to demolish a building in the Greenwich Village Historic District in order to make way for a new proposed $850 million hospital building. He also represented the NY Metropolitan Transportation Authority in successfully defending against challenges to the MTA’s 2003 decision to raise fares and tolls in the amount of $900 million.