--- title: "Preventive Medicine Expert Was Allowed to Opine on the Clinical and Operational Duties" meta: "og:description": "The preventive medicine expert was allowed to testify because he grounded his analysis in the medical records and treatment chronology" "og:title": "Preventive Medicine Expert Was Allowed to Opine on the Clinical and Operational Duties" author: "Expert Witness Profiler" description: "The preventive medicine expert was allowed to testify because he grounded his analysis in the medical records and treatment chronology" --- # Preventive Medicine Expert Was Allowed to Opine on the Clinical and Operational Duties Posted on December 8, 2025 by Expert Witness Profiler On January 28, 2021, Demetrius Nichols died while incarcerated at Menard Correctional Center. Plaintiff Diane Jones, Administrator of the Estate of Demetrius Nichols, filed this action against Wexford Health Sources, Inc., Dr. Mohammed Siddique, Ali Dearmond, NP, and Dr. Stephen Ritz, asserting wrongful death. Plaintiff retained [Ryan D. Herrington](https://expertwitnessprofiler.com/expert-witness/Ryan-Herrington/1543017), M.D., MPH to support her claims. Defendants filed a motion to exclude the testimony of Herrington. ## **Preventive Medicine Expert Witness** [Ryan Douglass Herrington](https://expertwitnessprofiler.com/expert-witness/Ryan-Herrington/1543017), M.D., MPH received his medical degree from the University of Virginia and a master’s degree in public health from the Ohio State University. He is licensed to practice medicine and is dual board certified by the American Board of Preventive Medicine in both public health/preventive medicine and addiction medicine. [Get the full story on challenges to Ryan Herrington’s expert opinions and testimony with an in-depth Challenge Study](https://expertwitnessprofiler.com/order/add?eId=1543017&pId=3). ## **Discussion by the Court** Herrington opined to a reasonable degree of medical certainty that: (1) from an asthma perspective, Nichols would have benefitted from earlier referral to otolaryngology; (2) Wexford practitioners’ repeated use of steroids for Nichols amounted to customary maintenance treatment for his nasal polyps; (3) Wexford’s custom of using steroids for nasal polyps was harmful for Nichols; (4) Wexford’s custom of using steroids for Nichols made it increasingly likely that he would suffer an asthma exacerbation; and (5) Wexford’s failure to provide Nichols a higher level of care on January 25, 2021 and on January 26, 2021 was a breach of the standard of care. ### **Qualification** Defendants argued that Herrington’s opinions should be excluded because he sought to opine on matters outside of his area of expertise and failed to review sufficient facts and data to form reliable opinions. Defendants further contended that his opinions are not grounded in reliable methodology. The Court disagreed. Herrington had the requisite background and experience to render opinions regarding the medical care Nichols received while incarcerated. He has over a decade of experience in correctional medicine, including as a former medical director of a state prison. Herrington testified that he was either directly or indirectly involved with every patient at those correctional facilities. His experience renders him qualified to opine regarding the clinical and operational duties at issue in this case. ### **Reliability** Defendants also argued that Herrington’s opinions are unreliable. In reaching his opinions, Herrington reviewed relevant case materials, including medical records and deposition testimony. He applied his extensive experience to evaluate the facts of this case and reached his conclusions regarding the medical care provided to Nichols. Herrington’s report includes a detailed methodology section in which he outlines and explains how he grounded his analysis in the medical records and treatment chronology. Herrington referenced numerous sources he relied on in formulating his opinions. Defendants’ disagreements with Herrington’s ultimate conclusions are not a justifiable basis to exclude his opinions. Defendants may certainly attempt to discredit Herrington on cross-examination or in their own presentation of the evidence. But their arguments go to the weight to be given Herrington’s testimony, not to its admissibility. The Court held that his opinions are relevant and will assist the jury with its analysis of whether Defendants’ care fell below accepted practice and caused or contributed to Nichols’ death. ## **Held** The Court denied the Defendants’ motion to exclude the testimony of Ryan Herrington. ## **Key Takeaway** In sum, the reliability of data and assumptions used in applying a methodology is tested by the adversarial process and determined by the jury; the court’s role is generally limited to assessing the reliability of the methodology — the framework — of the expert’s analysis. Defendants’ disagreements with Herrington’s ultimate conclusions are not a justifiable basis to exclude his opinions. ## **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/preventive-medicine-expert-was-allowed-to-opine-on-the-clinical-and-operational-duties/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/preventive-medicine-expert-was-allowed-to-opine-on-the-clinical-and-operational-duties/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/preventive-medicine-expert-was-allowed-to-opine-on-the-clinical-and-operational-duties/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/preventive-medicine-expert-was-allowed-to-opine-on-the-clinical-and-operational-duties/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/preventive-medicine-expert-was-allowed-to-opine-on-the-clinical-and-operational-duties/law-and-legal-expert-not-allowed-to-opine-on-contract-formation)