Mark H. M. Sosnowsky

Phone: (202) 354-1327
Fax: (202) 842-8465


Mark H. M. Sosnowsky concentrates his practice on complex litigation in federal and state courts, with a focus on white collar criminal defense, corporate investigations, health care fraud and compliance, antitrust, civil fraud and securities litigation.

Mark has extensive experience representing health care clients in compliance investigations and civil litigation, particularly False Claims Act litigation. He defends hospitals and other providers accused of violating the Anti-Kickback Statute and Stark Law, upcoding Evaluation and Management (E&M) services, overbilling Medicare for patients who did not satisfy inpatient criteria and other alleged fraud. He regularly represents clients in state and federal investigations and internal compliance audits and assists clients in developing effective compliance programs.

Mark defends companies and individuals against allegations of federal criminal violations and civil fraud offenses, and represents targets of corporate investigations, governmental inquiries and Congressional investigations. He handles matters involving alleged antitrust violations, environmental offenses, securities fraud, mail and wire fraud, government contracting fraud and regulatory violations, and has experience in multi-agency and cross-border investigations.

Mark routinely represents corporations and other entities facing False Claims Act investigations and lawsuits. His litigation experience extends to a variety of complex commercial matters, including products liability suits, trademark infringement and unfair competition claims, contract disputes, class actions and corporate governance matters. Drawing on his experience as a clerk for the Third Circuit, Mark has represented parties and amici curiae in appeals before the United States Court of Appeals for the District of Columbia, the United States Court of Appeals for the Federal Circuit, and the United States Supreme Court.


Bar Admissions

  • District of Columbia
  • Massachusetts
  • New Jersey
  • Pennsylvania
  • Virginia


  • Boston University School of Law, J.D., 2004, cum laude, Boston University Law Review
  • Pennsylvania State University, B.A., 1997

Court Admissions

  • U.S. Supreme Court
  • U.S. Court of Appeals, Federal Circuit
  • U.S. Court of Appeals, District of Columbia Circuit
  • U.S. District Court, District of Columbia
  • U.S. District Court, District of New Jersey
  • U.S. District Court, Eastern District of Pennsylvania
  • U.S. District Court, Eastern District of Virginia