Jack O’Neill has been trying large complex cases for over 45 years. His experience in the courtroom involves many cases that have been widely publicized.
O’Neill was co-trial counsel for UPR, Inc. in its attempted takeover of Pennzoil. He was lead counsel for Mitchell Energy Corporation in the company’s effort to overturn a $204 million judgment rendered against the company in a case tried for the company by another law firm. On appeal, argued by O’Neill, the case was reversed in its entirety and judgment was rendered in favor of Mitchell. He was lead trial counsel for Mitchell Energy in a related case in which plaintiffs sought $750 million for alleged contamination of their properties by natural gas and hydrogen sulfide. After a three-month trial, the jury rendered a unanimous verdict in favor of Mitchell. He was lead trial counsel for plaintiffs in the highly publicized Key 1-11 gas well blowout case in the Texas Panhandle, the largest blowout of a gas well in continental United States history. After a trial lasting over two and a half months, the jury returned one of the largest verdicts in Randall County, Texas history in favor of O’Neill’s clients. He was lead trial counsel for a well-known Houston oil and gas company in a fraud case in which the plaintiff sought damages in excess of $100 million. After a two-month trial, the jury returned a verdict for O’Neill’s client, and a take-nothing judgment was entered by the trial court. O’Neill has successfully tried many other cases relating to virtually all aspects of the oil and gas industry.
Lawdragon Honors
| Honor | Year | Practice |
|---|---|---|
| The 2027 Lawdragon 500 Leading Litigators in America | 2027 | Commercial Litigation |
| The 2026 Lawdragon 500 Global Leaders in Energy | 2026 | Energy & Natural Resources Litigation |
| The 2026 Lawdragon 500 Leading Litigators in America | 2026 | Commercial Litigation |
| The 2025 Lawdragon 500 Leading Energy Lawyers | 2025 | Energy & Natural Resources Litigation |
| The 2025 Lawdragon 500 Leading Lawyers in America | 2025 | Commercial Litigation |
| Lawdragon Announces 2025 Hall of Fame Inductees | 2025 | Litigation |
| The 2025 Lawdragon 500 Leading Litigators in America | 2025 | Commercial Litigation |
| The 2024 Lawdragon 500 Leading Lawyers in America | 2024 | Commercial Litigation |
| The 2024 Lawdragon 500 Leading Litigators in America | 2024 | Commercial Litigation |
O’Neill has won numerous jury verdicts in cases involving allegations of breach of contract, negligence and gross negligence, trademark infringement, unfair competition, fraud, environmental contamination and strict liability. Over the years, his clients have included Exxon Mobil Corporation, UNOCAL, Koch Industries, Inc., Stewart & Stevenson Services, Inc., The Williams Companies, GE, Eastman Kodak Company, INVISTA, Anadarko Petroleum Corporation, The John Wood Group, CNA, Transcontinental Gas Pipe Line Corporation, Mitchell Energy & Development Corp., Devon Energy Corporation, McKesson Corporation, Weatherford International, Inc., and many other Fortune 500 companies.
O’Neill is a former director of the Litigation Section of the State Bar of Texas. He also is a member of the American Board of Trial Advocates.