Expert Witness Profiler | Deep Research and Background Information on Experts

Colorado Court weighs reliable basis of Pathology Expert’s testimony over semantics in medical negligence suit 

Posted on August 31, 2023 by Expert Witness Profiler

Plaintiff, Deborah Duran pursued claims of medical negligence and malpractice against the Defendants, Donald Corenman, M.D.; Sean Bryant, M.D.; Jack Anavian, M.D.; The Steadman Clinic, Professional LLC; And Trystain Johnson, M.D. arising from the untimely death of her husband, Gilbert Duran due to a rare melanic schwannoma. Plaintiff is not only Mr. Duran’s widow but also acted as the personal representative of her late husband’s estate. The core contention in this case was that the Defendants, purported medical professionals, had delayed in diagnosing Mr. Duran’s schwannoma upon its initial discovery in 2015. This alleged delay led to the tumor metastasizing, ultimately resulting in Mr. Duran’s demise in 2019. Plaintiff sought to preclude certain opinions of defense expert Dr. Gross regarding the tumor’s likely characteristics and poor prognosis in 2015, but the Court admitted it regardless because it weighed reliable basis over semantics dispute. 

Anatomic Pathology Expert 

John McMahon Gross, M.D., M.S. had been designated by the Defendants to provide expert testimony regarding the pathology issues in this case and offer an opinion on the likely characteristics of the tumor back in 2015. Following pathology residency, Dr. Gross pursued specialized fellowship training in bone and soft tissue at the University of Washington in Seattle, WA followed by additional fellowship training in surgical pathology at the Mayo Clinic in Rochester, MN. In 2020, Dr. Gross became an assistant professor in the Department of Pathology at Johns Hopkins where he specializes in bone and soft tissue and surgical pathology. Dr. Gross has an academic interest in bone and soft tissue tumors and has authored over a half dozen articles and chapters and given national and international presentations on sarcoma pathology. Dr. Gross’s stance was that the tumor had been malignant in 2015, carrying a grim prognosis even with early intervention. 

The Plaintiff sought to exclude a specific facet of Dr. Gross’ expert opinion from consideration. 

Discussions by the Court 

Citing his March 30, 2022 expert report, the Plaintiff presented several arguments to strike Dr. Gross’ opinion that increased mitotic activity predicted malignancy. First, the Plaintiff contended that Dr. Gross had failed to provide supporting medical literature for this opinion which rendered it unsupported and undermined its credibility. Second, the Plaintiff argued that this opinion was irrelevant to the central issues of the case since it lacked empirical backing to contribute meaningfully to the understanding of Gilbert Duran’s circumstances. Third, even if considered relevant, the Plaintiff invoked Rule 403 of the Federal Rules of Evidence which suggested that any potential probative value of the unsupported opinion was outweighed by its potential for confusion or prejudice. 

In response, the Defendants asserted that the Plaintiff’s contentions were mischaracterizations of Dr. Gross’ opinion and its underpinnings. They argued that the Plaintiff had introduced the term “predict” during the deposition, whereas Dr. Gross had framed his opinion as an association or correlation between mitotic activity and poor prognosis. The Defendants further maintained that Dr. Gross’ opinion was built upon sufficient facts and data and highlighted the Plaintiff’s own reference to the Torres-Mora study that supported his stance and was thoroughly discussed during Dr. Gross’ deposition. The Defendants contended that Dr. Gross’ opinion was reliable, relevant, and logically derived from existing scientific knowledge. 

In conclusion, the Court faced the critical task of evaluating the admissibility of Dr. Gross’ opinion, specifically his opinion which suggested an association or correlation between high mitotic rates and poor prognosis. The outcome of this decision held significant weight, as Dr. Gross’ expert testimony had the potential to shape the Court’s understanding of the medical aspects of the claim. Balancing the arguments presented by both parties, the Court’s determination would impact the course of the case and potentially influence the attribution of liability and the assessment of damages. 

Plaintiff’s central argument revolved around their assertion that Dr. Gross intended to provide testimony which suggested that increased mitotic activity in 2017/2018 predicted aggressive behavior of tumors and was predictive of the tumor in 2015. The Plaintiff equated this opinion with the notion that mitotic rate predicted malignancy. Additionally, the Plaintiff emphasized the viewpoint of Dr. Folpe, Dr. Gross’ mentor and a respected expert in the field, who disagreed with Dr. Gross’ opinion and did not subscribe to the belief that mitotic rate predicted metastasis. The Plaintiff fervently urged the Court to strike Dr. Gross’ opinion about increased mitotic activity being predictive of aggressive behavior. 

The Plaintiff conflated the term “predicts” with “causation” in their argument which further intensified the matter. They illustrated this by drawing an analogy which asserted that just as a correlation between ice cream sales and shark attacks did not imply that consuming ice cream caused shark attacks, a similar principle applied to the correlation between increased mitotic activity and metastasis. The Plaintiff contended that association was never the same as prediction and exemplified this with the analogy of a person associating with a criminal not necessarily predicting that the individual will commit a crime themselves. 

However, the Court concurred with the Defendants’ stance that the Plaintiff aimed to exclude an opinion that Dr. Gross did not actually present. After carefully examination of Dr. Gross’ written opinion and deposition testimony, it was apparent that the core of his written opinion centered on Mr. Duran’s tumor being an exceptionally rare type of sarcoma which possessed aggressive traits and a malignant histology. Dr. Gross maintained that the aggressive features noted in the tumor’s 2018 diagnosis were likely present in 2015 which indicated a bleak prognosis even if diagnosed earlier. He argued that the aggressive nature of the tumor would have made a significant impact even if treated in 2015. Dr. Gross concluded by stating that the tumor’s aggressive attributes and the presence of these traits in 2018 imply their existence in 2015, and that early diagnosis and treatment may not have prevented recurrence or metastasis. 

Contrary to the Plaintiff’s assertions, nowhere in Dr. Gross’ report did he offer the specific opinion that a high mitotic rate predicted malignancy. Even during his deposition testimony, when asked about whether he believed that mitotic activity was predictive of malignant behavior, Dr. Gross responded by saying that it had been associated with a worse prognosis. Despite further pressing from the Plaintiff’s counsel, Dr. Gross consistently maintained that mitotic activity had been merely suggestive or associated with an unfavorable outcome. 

In conclusion, the Plaintiff’s argument hinged on the interpretation that Dr. Gross asserted a predictive link between increased mitotic activity and aggressive behavior of tumors. However, the Defendants and the Court contended that Dr. Gross’ opinion did not explicitly express such a predictive relationship, but was suggestive of a relationship of association between a poor prognosis and high mitotic activity present in the subject tumor. This nuanced distinction became pivotal in determining the admissibility and weight of Dr. Gross’ expert testimony within the context of the case. 

The crux of the dispute in this case appeared to center around a semantic distinction. The Plaintiff seemingly equated the phrase “predictive of” with terms like “caused” or “causation.” However, the Court did not find that Dr. Gross’ opinion, as articulated in both his written report and deposition testimony, could be interpreted as encompassing a notion of prediction. Furthermore, even if it were assumed to involve prediction, in the realm of medicine, “predictive” did not necessarily denote causation. The term “predictive value” in a medical context, as defined by Stedman’s Medical Dictionary, referred to the likelihood that a given test result correlates with the presence or absence of a disease. This definition aligned with Dr. Gross’ medical opinion and underscored the Court’s understanding that his opinion was grounded in a correlation, not a statement of causality. In other words, the court weighed the reliable basis over semantics. 

The Plaintiff’s challenge to Dr. Gross’ qualifications or experience did not seem to hold weight in this argument. Dr. Gross evidently derived his opinions not solely from referenced medical literature and scientific sources, but also from his substantial education, training, and experience as a pathologist. Moreover, the Court deemed the Torres-Mora study and the World Health Organization Classification of Tumors – Soft Tissue and Bone Edition (5th Ed.), in conjunction with other factors referenced in Dr. Gross’ report, as sufficient support for his opinion. This collective foundation rendered his opinion adequately reliable. 


Dr. Gross’ opinion regarding any observed association, suggestion, or correlation between heightened mitotic activity and a poor prognosis in the specific tumor in question was indeed relevant to the Plaintiff’s claim of delayed diagnosis and the Defendants’ defenses. Considering all factors, the Court found no substantial basis under Fed. R. Evid. 403 to exclude Dr. Gross’ opinion from the proceedings. This ruling acknowledged the relevance, reliability, and context of Dr. Gross’ testimony within the broader framework of the case. 

The Defendants have effectively fulfilled their obligation to demonstrate that Dr. Gross’ opinion met the criteria stipulated in Fed. R. Civ. P. 702. It is worth noting that the Plaintiff retained the prerogative to subject Dr. Gross to thorough and respectful cross-examination regarding the matters addressed in her motion and during Dr. Gross’ deposition. Consequently, the Court denied the motion and upheld the admissibility of Dr. Gross’ opinion as evidence in the case. Since the remaining issues are yet to be resolved, the Court has not reached a final outcome for this case as of now.

Key Takeaways 

  1. The Court rejected the Plaintiff’s argument that the expert’s opinion lacks sufficient basis and should be excluded as irrelevant or prejudicial. 
  1. The Court found the defense expert does not actually opine that mitotic activity predicts tumor metastasis or malignancy, only that there is an association or correlation between high mitotic rates and poor prognosis. 
  1. The Court viewed the dispute over the language used by the expert as merely semantic in nature. The term “predictive” does not necessarily imply causation in a medical context. 
  1. The Court held the expert’s opinions are sufficiently reliable based on his qualifications/experience as a pathologist and the medical literature cited in his report. 
  1. The Court found the expert’s views relevant to the issues in the medical malpractice case regarding delayed diagnosis and defenses. 
  1. The Court ruled the defense satisfied its burden under Rule 702 to show the testimony is admissible expert opinion. 
  1. The Court emphasized the Plaintiff can vigorously cross-examine the expert about his opinions at trial. 
  1. The Court denied the motion to strike/preclude the expert’s testimony, allowing him to offer opinions at trial on the characteristics of the tumor and likely prognosis. 

In summary, the key takeaways are that the Court allowed the defense expert to testify despite Plaintiff’s challenges, finding his opinions supported, relevant, and reliable based on the appropriate expert methodology and standards. The Court saw flaws only in the semantics used to describe the opinion, not the underlying basis.