Mr. O’Neill specializes in civil litigation. He is primarily involved in business, commercial and insurance litigation and the defense of personal injury actions. He has extensive experience in defending claims based on product liability, medical malpractice, industrial, oil field, construction, trucking and traffic accidents, in addition to wrongful death, premises liability, recreational industry accidents, insurance coverage and bad faith.  Mr. O’Neill also has significant experience in governmental liability and civil rights claims.

Prior to law school, Mr. O’Neill worked in a variety of agricultural businesses in the upper Midwest, and his family continues to be involved in the livestock and agriculture industry.

Before joining Welborn Sullivan Meck & Tooley, P.C. Mr. O’Neill practiced with Brown, Drew & Massey, LLP for fourteen years.

Representative Matters

  • 1990-1991, Law Clerk to the Honorable Clarence A. Brimmer, then Chief Judge of the United States District Court for the District of Wyoming
  • Represented multiple operators, drillers and oil field service providers in defending against variety of serious personal injury and wrongful death claims
  • Represented liability insurer in seminal insurance bad faith case before Wyoming Supreme Court
  • Represented Canadian trucking company in multi-year, multi-lawsuit litigation arising from series of catastrophic accidents on I-80 in Wyoming
  • Represented European ski binding manufacturer in successfully contesting existence of personal jurisdiction in Wyoming
  • Represented Wyoming local government entities in defending against variety of civil rights claims

Publications, Presentations & Accolades

  • Named the Best Lawyers® 2018 Personal Injury Litigation-Defendants "Lawyer of the Year" in Casper
  • Selected for Inclusion in The Best Lawyers in America® in the field of Personal Injury Litigation - Defendants, 2016-2020
  • Member, Wyoming Bar Association
  • Admitted to practice before all district courts in Wyoming and the Wyoming Supreme Court
  • Admitted to practice in the Federal District Court in Wyoming and the United States Court of Appeals for the Tenth Circuit
  • Author, Lawyers Cooperative Publishing, Cumulative Supplement, Wyoming Trial Handbook


Mr. O’Neill and his wife, Sher, have four children and enjoy hunting, fishing, skiing and all activities in Wyoming’s outdoors.

* Per Wyoming Rule of Professional Conduct 7.1 (c), the descriptions of our fields of practice do not state or imply certification, specialization or expertise in any particular area of law, unless the description specifically states that the particular lawyer holds a certification or other expertise recognized by the applicable State Bar or regulatory authority.


Practice Areas
  • Litigation

  • J.D., University of Wyoming Law School, 1990
  • B.A., St. John’s College, Santa Fe, NM, 1986

  • Wyoming, 1991*
  • Colorado, 1990
  • Minnesota, 2000
  • U.S. District Court, District of Wyoming, 1991
  • U.S. Court of Appeals, Tenth Circuit, 1992

Professional & Community Activities
  • Wyoming State Bar
  • Defense Research Institute
  • Member, Board of Trustees, Casper Family YMCA
  • Past President, Board of Directors, Casper Family YMCA
  • Past President, Natrona County Library Board
  • Past President, Natrona County Bar Association, 1998-1999