William P. Ziegelmueller

Bill is a seasoned trial lawyer who represents individual and corporate clients in federal criminal investigations, regulatory enforcement actions, civil litigation, and corporate internal investigations.
Bill Ziegelmueller, Partner at ArentFox Schiff LLP

Bill has experience in federal district and appellate courts across the country, including first-chair trial experience in both civil and criminal cases.

He represents corporations and individuals accused of alleged wrongdoing, such as fraud, political corruption, tax evasion, extortion, bribery, foreign corrupt practices, and antitrust violations. Bill is familiar with the technical coding and billing requirements of federal health care programs, and he frequently advises health care providers in responding to government audits and subpoenas, and, if necessary, in litigating civil or criminal charges. He also counsels providers in defending against claims brought by whistleblowers or qui tam relators.

Bill has experience in defending clients involved in investigations and enforcement actions conducted by the SEC, IRS, EPA, CFTC, OCC, ICE, FDA, USDA, and other federal and state regulatory agencies. He has been involved in several investigations related to the EB-5 visa program, government purchasing rules, anti-dumping duties, and the marketing of pharmaceuticals. Bill also has responded to numerous investigative inquiries by the Illinois Attorney General, the Department of Financial and Professional Regulation, and other state regulators, and he has litigated consumer fraud and professional licensing matters in both administrative and judicial proceedings.

His civil litigation has involved a range of executive employment and compensation disputes, unfair competition and corporate breach of contract cases, and insurance matters.

Client Work

  • Lead trial counsel in winning a not guilty verdict on bank fraud charges for our client, who was charged in the Eastern District of Texas with defrauding lenders through real estate transactions designed to take advantage of a federal tax incentive implemented after Hurricane Katrina.
  • Represented key players in many high-profile criminal investigations, including the General Motors’ ignition switch and Takata airbag recalls, and the federal inquiry into United Airlines’ ties to the Port Authority of New York and New Jersey.
  • Represented Antoin Rezko, an advisor to former Illinois Governor Rod Blagojevich, in a three-month trial in Chicago.
  • Represented the lead defendant in the TAP Pharmaceuticals case, which culminated in the acquittal of all individual defendants after a three-month jury trial in Boston.
  • Led discovery and was second chair in the trial defense of a Blue Cross/Blue Shield of Illinois executive, which ended in an acquittal after a lengthy trial in the Southern District of Illinois.
  • Represented a former attorney who was charged with developing complex tax shelters promoted by major law firms, banks, and brokerage houses during a four-month trial in New York.
  • Led the trial defense of the owner of a California pharmacy charged with criminal health care fraud offenses.

Boards, Memberships & Certifications

  • American Bar Association
  • Chicago Bar Association
  • Seventh Circuit Bar Association

Publications, Presentations & Recognitions


  • “Are You Ready for COVID-19 Litigation?” Webinar (Aug. 13, 2020)


  • The Best Lawyers in America, Best Lawyers (2021-2024)
  • Chambers USA – Litigation: White-Collar Crime & Government Investigations, Illinois (2021-2024)
  • Illinois Super Lawyers, Thomson Reuters (2010-2023)
  • Illinois Leading Lawyer, Law Bulletin's Illinois Leading Lawyers Network (2017-2023)
  • Peer-Reviewed AV® Preeminent™, Martindale-Hubbell (Since 2016)
  • Illinois Rising Star, Thomson Reuters Illinois Super Lawyers (2009)



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