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Mark A. Thornhill

  • T: 816.292.8119
    F: 816.474.3216
  • Kansas City

Mark Thornhill represents individuals and organizations in white collar criminal and regulatory cases. His white collar work started as a prosecutor with the United States Department of Justice - Criminal Tax Section. At Spencer Fane, Mark has defended the full array of white collar cases - anti-trust, bank fraud, computer fraud, environmental, healthcare, mail fraud/wire fraud and tax evasion, among others. In regulatory cases, Mark has represented individuals and companies before the Securities and Exchange Commission, the Financial Institutions Regulatory Authority (FINRA), the Public Company Accounting Oversight Board (PCAOB), the Federal Reserve Bank and the Environmental Protection Agency.

Mark also conducts internal investigations. In an investigation for a large Midwest bank, Mark uncovered more than $1 million in fraudulent transactions by the bank president. Mark’s investigation for an IT company revealed more than $200,000 in unauthorized payments to the CEO. Mark recently worked with the National Institute for Trial Advocacy to develop an internal investigation instructional program.

Mark's civil trial focus is on fiduciary duty cases. He has defended domestic and foreign companies or their directors in fiduciary duty trials in courts in the mid-west and in Delaware. These cases have included issues of cash-out mergers, customary practices in Europe, aiding and abetting, loyalty disputes and a broad range of evaluation techniques, among other issues. Mark also represents a national life and disability insurance company against lawsuits in Missouri, Kansas and Southern Illinois.


  • Trial victory for a Europe-based ventilation company against a fiduciary duty claim in the Delaware Court of Chancery. This case focused on the conduct of a joint-venture party when the other venture party was beset with internal dissension.
  • Represented a Native-American corporation in an investigation of federal criminal laws related to tax liabilities. Indictments were issued against nineteen companies and individuals. Mark’s client was not indicted.
  • Represented a construction company manager in connection with criminal violations of Clean Water Act. The manager was indicted on four felony charges. The case was resolved through the manager’s plea to a misdemeanor.


  • 2015 Vice Chair of the Board, Planned Parenthood of Kansas and Mid Missouri
  • 2004-05 Chairman of the Board of Truman Medical Centers (Kansas City’s academic hospital)
  • 1996 Chairman of the Board, Kansas City Free Health Clinic (Now Kansas City Care Clinic)


  • Selected to The Best Lawyers in America® since 2008 for White Collar Practice
  • Selected as Best White Collar Lawyer in Western Missouri in 2014
  • Selected to Super Lawyers® for Commercial Litigation Practice since 2007


Contact Mark Thornhill at 816.292.8119 or .

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