--- title: "Expert’s Legal Conclusions Advocating for Class Certification Excluded" meta: "og:description": "The expert offered legal opinions about whether the proposed class should be certified under the Rule 23 factors" "og:title": "Expert’s Legal Conclusions Advocating for Class Certification Excluded" author: "Expert Witness Profiler" description: "The expert offered legal opinions about whether the proposed class should be certified under the Rule 23 factors" --- # Expert’s Legal Conclusions Advocating for Class Certification Excluded Posted on June 2, 2025 by Expert Witness Profiler This putative class action was initiated by Plaintiffs, a group of individuals who are leaseholders of oil and gas leases, against Defendant XTO Energy Inc (“XTO”) alleging that XTO breached their leases when it deducted unreasonable and excessive post-production costs from their royalty payments. Therefore, XTO filed a motion to exclude certain opinions of Plaintiffs’ expert [John Burritt McArthur](https://expertwitnessprofiler.com/expert-witness/John-McArthur/1547688) (“McArthur”) regarding class certification under [Federal Rule of Evidence 702](https://www.law.cornell.edu/rules/fre/rule_702#:~:text=Rule%20702%20sets%20forth%20the,is%20a%20relatively%20narrow%20inquiry.). ## **Law and Legal Expert Witness** [John Burritt McArthur](https://expertwitnessprofiler.com/expert-witness/John-McArthur/1547688) has been serving as an arbitrator for 22 years and working as a trial lawyer, representing Plaintiffs and Defendants in courts around the country, for 33 years. He has offices in Berkeley California and in Houston and is a past partner of Susman Godfrey LLP in Houston and Hosie McArthur LLP of San Francisco, both firms with national trial dockets. Also, McArthur was Editor in Chief of the Texas Law Review, a Chancellor, and a member of the Order of the Coif in law school. He is a Phi Beta Kappa, magna cum laude graduate of Brown University. Moreover, McArthur clerked for Judge Joseph Sneed on the Ninth Circuit after law school. In addition to his J.D., he holds an M.A. in economics, an M.P.A. from Harvard University’s Kennedy School of Government, and has graduate-level economics training from the London School of Economics and a Ph.D in public policy from the Goldman School of Public Policy at the University of California (Berkeley). [Get the full story on challenges to John Burritt McArthur’s expert opinions and testimony with an in-depth Challenge Study.](https://expertwitnessprofiler.com/order/add?eId=1547688&pId=2) ## **Discussion by the Court** XTO argues that portions of McArthur’s reports should be stricken because McArthur improperly offers legal conclusions advocating for class certification under  [Fed. R. Civ. P. 23](https://www.law.cornell.edu/rules/frcp/rule_23). Plaintiffs did not dispute that McArthur’s reports consisted of some legal conclusions (and indicated they did not intend to offer that testimony as an expert opinion) but maintained the reports also consisted of testimony based on industry standard in the oil and gas field. However, the Court held that McArthur’s reports highlighted by XTO largely offered legal opinions about whether Plaintiffs’ proposed class should be certified under the Fed. R. Civ. P. 23 factors and will not be considered in the forthcoming recommendation on the motion for class certification. However, to the extent McArthur’s expert reports contain opinions based on standards, customs and practices of the oil and gas industry, the Court will consider those opinions where relevant. ## **Held** The Court granted XTO’s motion to exclude certain legal opinions by Plaintiffs’ expert John Burritt McArthur. ## **Key Takeaway**: Basically, experts are allowed to testify about customs and practices in a field of business but not whether those customs or practice complied with the law or regulations. Therefore, where an expert offers a legal opinion, the court must “exclude opinions phrased in terms of inadequately explored legal criteria.” ## **Case Details:** --- ## **You Might Also Like** ![Human Resources Expert Allowed to Opine on Termination](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-22T200052.311.jpg) [**Human Resources Expert Allowed to Opine on Termination**](https://expertwitnessprofiler.com/experts-legal-conclusions-advocating-for-class-certification-excluded/human-resources-expert-allowed-to-opine-on-termination)![Neuropsychology Expert Not Allowed to Opine on Cognitive Decline](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-22T144728.528.jpg) [**Neuropsychology Expert Not Allowed to Opine on Cognitive Decline **](https://expertwitnessprofiler.com/experts-legal-conclusions-advocating-for-class-certification-excluded/neuropsychology-expert-not-allowed-to-opine-on-cognitive-decline)![Human Factors Expert Not Allowed to Opine on the Tile](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-21T191749.960.jpg) [**Human Factors Expert Not Allowed to Opine on the Tile**](https://expertwitnessprofiler.com/experts-legal-conclusions-advocating-for-class-certification-excluded/human-factors-expert-not-allowed-to-opine-on-the-tile)![Insurance Expert Not Allowed to Opine on Legal Duties](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-21T155751.487.jpg) [**Insurance Expert Not Allowed to Opine on Legal Duties**](https://expertwitnessprofiler.com/experts-legal-conclusions-advocating-for-class-certification-excluded/insurance-expert-not-allowed-to-opine-on-legal-duties)![Law And Legal Expert Not Allowed to Opine on Contract Formation](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-20T213123.718.jpg) [**Law And Legal Expert Not Allowed to Opine on Contract Formation**](https://expertwitnessprofiler.com/experts-legal-conclusions-advocating-for-class-certification-excluded/law-and-legal-expert-not-allowed-to-opine-on-contract-formation)