Mark Harris is a partner at Proskauer Rose LLP and co-head of its Appellate Practice Group, which was honored in 2011 by Law360 as one of five Appellate Practices of the Year nationally, and by the National Law Journal with a spot on its annual “Appellate Hot List.”  Most recently, the American Lawyer named Mark its “Litigator of the Week” for his representation of Biosig Instruments before the Federal Circuit and the U.S. Supreme Court.  Mark is also a member of Proskauer’s White-Collar Defense & Investigations and Securities Litigation Groups, concentrating his practice in the areas of white-collar criminal defense and related litigation, and representing both institutional and individual clients in government investigations and prosecutions.

Mark is a former clerk to U.S. Supreme Court Justices John Paul Stevens and Lewis Powell, Jr., and to Judge Joel Flaum of the U.S. Court of Appeals for the Seventh Circuit. Mark served as an Assistant U.S. Attorney for the Southern District of New York, during which he prosecuted a broad spectrum of federal crimes, including health-care fraud, financial fraud, and corporate embezzlement, and tried a number of jury trials and argued before the Second Circuit.

Mark has handled dozens of cases in the U.S. Supreme Court and other appellate courts in areas spanning criminal law, sentencing, copyright, labor relations, employment law, and administrative law.  In 2015, he successfully represented Nextel Communications before the Second Circuit, which vacated the certification of a class of hundreds of former employees who had brought fiduciary and other claims against the company.  In some of his other major cases, he served as co-counsel to the petitioner in Hill v. United States, in which the Supreme Court applied the Fair Sentencing Act of 2010 to benefit defendants retroactively; he helped persuade the Second Circuit to reverse the conviction of a former Gen Re executive; he successfully represented electronic publishers before the Supreme Court in Reed Elsevier Inc. v. Muchnick, named the 2010 “U.S. Copyright Case of the Year” by Managing Intellectual Property Magazine; and he briefed and argued the American Bar Association’s successful challenge to the Federal Trade Commission’s “Red Flags Rule.”

Since 1996, Mark has been a member of the Board of Editors of the Federal Sentencing Reporter and a frequent contributor. His work on behalf of non-U.S. clients was featured in the American Lawyer’s 2006 Litigation supplement. He has lectured on both appellate practice and criminal law before the International Bar Association, the National Association of Criminal Defense Lawyers, PLI, and the ABA Sections of Litigation, Criminal Law, and Employment and Labor Law.  He has appeared on WCBS-TV , NY1, Bloomberg Radio, FM News 101.9, and WINS AM-1010, and has been featured in the National Law Journal, New York Law Journal, Law360, Legal Times, and other publications.

Related Practices


White Collar Defense & Investigations

Securities Litigation

Non-Compete & Trade Secrets


Harvard Law School, J.D., 1992
magna cum laude

Supervising Editor, Harvard Law Review

Harvard College, A.B., 1989
magna cum laude
Phi Beta Kappa

Bar Admissions

New York


District of Columbia

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