Shawn O'Brien - McDermott Will & Emery


Shawn O’Brien is nationally recognized by his peers and clients as a leading tax practitioner with a focus on tax disputes and controversies involving state, federal and international tax authorities. Drawing on his 25 years of experience, Shawn represents clients in tax examinations and administrative appeals and, when necessary, serves as a forceful advocate in litigation before the US Tax Court, US district courts, the US Court of Federal Claims, state courts and federal appellate courts.

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  • Represent Apache Corporation, a publicly traded oil and gas exploration and production company, in the Tax Court for tax disputes involving carrybacks of specified liability losses and research and development credits (Apache Corporation v. Commissioner)
  • Represented US Venture, a large fuel distribution company, in the District Court for the Eastern District of Wisconsin involving the federal alternative fuel mixture credit (US Venture v. United States)*
  • Represented EOG Resources, Inc., a publicly traded oil and gas exploration and production company, in the Tax Court for a tax dispute involving the alternative minimum tax resulting from the company’s hedging program (EOG Resources, Inc. v. Commissioner)*

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  • Chambers USA, 2015 to 2023, Tax: Litigation – Texas
  • International Tax Review, 2013 to 2023, Tax Controversy Leader


  • Internal Revenue Service Advisory Council (IRSAC), past chair of the Large Business & International subcommittee, 2016 to 2018
  • State Bar of Texas Tax Section, past chair of the Energy and Natural Resources Committee, 2011 to 2013


New York University School of Law, LLM, 1998
Loyola Law School, JD, 1997
Millsaps College, BBA, 1993

US District Court for the Southern District of Texas
US Court of Federal Claims
US Tax Court