Colorectal Surgery Expert Was Allowed to Opine on Ongoing Medical Complications

On April 5, 2021, Thomas Riles was arrested for speeding and other traffic offenses. He was detained for several hours at the Carroll County Detention Center. Riles has an uncommon ileostomy, known as a Barnett Continent Intestinal Reservoir (“BCIR”), which requires specialized medical equipment to empty feces from the surgically created pouch inside his abdomen. The officers involved in his arrest and detention did not make that equipment available to him while he was in custody. He was unable to empty the feces from his internal ileostomy pouch for the duration of his approximately seven-hour detention.

The parties dispute whether the delay in being able to empty his pouch damaged the pouch such that Riles could no longer drain feces at will and must instead be permanently catheterized. Permanent catheterization comes with the risk of stool leaking from the catheter. Before his arrest, Riles worked a sales job in the food and beverage industry. After his arrest, he lost business when he could no longer enter sterile food production facilities because of that risk.

Defendant Laralyn Koster, an officer with the Carroll County Sheriff’s Office, sought to exclude the testimony of Riles' damages expert, Mark T. McKinnon, and medical expert, Dr. Ernest Rehnke. Plaintiff’s motion in limine sought to limit the testimony of Defendant’s medical expert, Dr. Jason S. Mizell.

Economics Expert Witness

Mark Thomas McKinnon works for McKinnon Economics Consulting and is a member of the American Academy of Economic and Financial Experts. He has been serving as an expert witness since 2014, testifying in approximately eighty-nine cases.

Want to know more about the challenges Mark McKinnon has faced? Get the full details with our Challenge Study report.

General Surgery Expert Witness

Ernest Rehnke practiced general and vascular surgery in St. Petersburg, Florida for over 30 years. Throughout his career, Rehnke created and managed continent ileostomies for approximately 3,000 patients.

Get the full story on challenges to Ernest Rehnke’s expert opinions and testimony with an in-depth Challenge Study.

Colorectal Surgery Expert Witness

Dr. Jason Scott Mizell is a board-certified colorectal surgeon who has been practicing for many years.

Gain a comprehensive understanding of Jason Mizell's qualifications and casework history with his Expert Witness Profile report.

Discussion by the Court

A. Motion to Disqualify Expert Mark McKinnon

Based on earnings information provided by Riles, McKinnon calculated wage loss damages (including future wage loss and/or impairment) in the total amount of $6,812,851. This calculation assumes the accuracy of Riles’ (alleged) earnings over a thirteen-month period that occurred after the April 2021 incident at the jail––and prior to an (allegedly) related incident/complication that Riles suffered in February 2024. In that interim window, Riles says he was employed by MDC Consulting, LLC, a company he co-founded in 2022. McKinnon does not know, and the record does not otherwise explain what MDC Consulting does. The Court only knows that Riles describes himself as a senior project manager and salesman.

To prepare his calculations, McKinnon reviewed the Complaint, Riles’ 2018–2021 tax returns, and a document prepared by Riles titled “Thomas Riles Earnings and Equity Report.” The Earnings Report included columns indicating “payroll received,” “mileage,” and “sales commission total” for the thirteen months between February 2023 and February 2024, which totals $428,061.

McKinnon divided the total by thirteen and then multiplied by twelve to arrive at annualized income of $395,134. McKinnon then accepts as true Riles’ own estimate that he has or will lose 80% of that annual income as a direct result of the February 2024 incident/complication.

Koster is critical of the facts that McKinnon used to prepare his expert report. For example, McKinnon’s wage loss opinions are premised on the assumption that Riles had $395,000 in annualized income in 2023, the only evidence of which is Riles’ own self-serving representation. At the same time, McKinnon elected to ignore the income Riles reported on his tax returns for several years prior to his April 2021 arrest and detention––which was relatively minimal. Although Koster frames her argument as one about the factual basis of McKinnon’s testimony, it is more properly understood as an attack on the assumptions underlying his opinions.

In the Court’s view, McKinnon’s expert role is that of a glorified number cruncher— “glorified” in the sense that he must necessarily incorporate his expertise in selecting and applying an appropriate discount rate to present value calculations. Koster is not critical of the number crunching: she does not challenge the discount rate or the mathematical formula used to calculate present value. Instead, she disputes the factual assumptions used by McKinnon in his present value tables. To that point, McKinnon readily concedes that his wage loss opinions are only as accurate as the information he has been asked to assume. Typically, however, challenges to an economist’s assumptions regarding future lost wages go to the weight and not the admissibility of the testimony.

The Court granted Defendant’s motion to disqualify expert Mark McKinnon to the extent that McKinnon may not opine that Riles’ annual income was, in fact, $395,000 in 2023, nor may he opine that Riles’ earning capacity has been impaired by 80%; but the Court denied the motion to the extent that McKinnon may use factual assumptions (as supported by the evidence at trial) to opine about mathematical calculations and economic considerations, including discount rates, present value calculations, and life expectancy tables. A ruling as to whether any specific factual assumption is supported by sufficient facts or data is deferred until trial.

B. Motion to Disqualify Expert Dr. Ernest Rehnke

Koster sought to exclude Riles’ medical expert, Dr. Ernest Rehnke, arguing that his opinions are factually unsupported for two reasons. First, Koster argued that Rehnke improperly failed to rule out obvious alternative causes of Riles’ medical complications. Second, Koster claimed that Rehnke’s opinion is based on insufficient data because he did not know the number of times that Riles typically intubated his BCIR.

Rehnke treated Riles between 2010 and 2017, during which Rehnke created and repaired a BCIR for him. Rehnke contended that Riles has a damaged valve that does not function properly due to the delay in care Riles experienced on April 5, 2021. Rehnke’s expert report states that because of the delay, Riles suffers “ongoing significant social, physical, and financial disabilities with the possibility of early death.” Rehnke opined that “it is more likely than not that Riles’ lifespan has been significantly foreshortened as a direct result of being denied the ability to empty his BCIR on April 5, 2021.”

Koster’s primary argument is that Rehnke should have conducted a differential diagnosis to determine the cause of Riles’ continuing medical complications. Koster argued that Rehnke did not rule out three other potential causes. These include Riles’ consistent valve problems before April 5, 2021, other issues related to Gardner’s Syndrome, and a later incident during which Riles went nine hours without access to the equipment required to intubate his BCIR.

Koster claimed that a Plaintiff’s expert “must ‘rule in’ the suspected cause of the injury and also ‘rule out’ other possible causes.” The Court disagreed. Differential diagnosis is a method of determining causation by which an expert “determines all of the possible causes for the patient’s symptoms and then eliminates each of these potential causes until reaching one that cannot be ruled out, or deduces which of those that cannot be excluded is the most likely.”

The Court will not exclude Rehnke’s opinion on the basis that he did not rule out all possible causes of Riles’ medical complications. Rehnke’s report is based on Riles’ deposition and a review of his medical history, including his records from when he was Rehnke’s patient. A review of Riles’ medical record necessarily includes the many complications he suffered prior April 5, 2021, and his medical history after April 5, 2021. Although Rehnke does not state explicitly that he ruled out other potential causes, such as Gardner’s Syndrome, his report and testimony suggest that he did. For instance, in Rehnke’s deposition, he considered the effects of Gardner’s Syndrome on Riles’ health. He testified to the ways in which Gardner’s Syndrome can lead to future health problems. Yet, he ultimately concluded that Gardner’s Syndrome was the not the cause of Riles’ current suffering.

The Court concluded that Rehnke’s causation opinion is sufficiently reliable and factually supported. Koster’s issue with Rehnke’s opinion is an attack on the completeness of Rehnke’s methodology. Such an attack goes to the weight and not the admissibility of his testimony.

Koster also argued that Rehnke’s opinion is unreliable because it is based on insufficient data. She claims that because Rehnke did not know the number of times that Riles intubates his BCIR, he could not reasonably conclude that a delay in intubating caused Riles’ current complications.

Although Rehnke concedes in his deposition that he did not know how frequently Riles was intubating in April 2021, Riles’ medical record suggests that he was intubating multiple times a day. Like Koster’s first argument, this claim goes to the completeness of Rehnke’s methodology. It does not provide independent grounds to exclude his testimony.

Accordingly, the Court denied the Defendant’s motion to exclude the testimony of Dr. Ernest Rehnke.

C. Motion to Limit Testimony of Dr. Jason Mizell

Plaintiff’s motion in limine sought to limit the testimony of Defendant’s medical expert, Dr. Jason Mizell. Mizell’s report posits that “the delay in Riles being able to catheterize his BCIR did not lead to clinically significant damage to his BCIR, did not subject him to an increase in procedures or surgeries, or lead to a foreshortened life.” Instead, Mizell opined that Riles’ ongoing medical complications are attributable to his complicated medical history and lifestyle choices.

Riles sought to exclude the portions of Mizell’s report that attribute Riles’ ongoing medical problems to his pre-existing conditions and lifestyle choices, claiming these opinions are irrelevant and unfairly prejudicial. Riles argued that Mizell should have considered the effect of Koster’s conduct on April 5, 2021.

Attacks on the factual basis of Mizell’s conclusion go to the weight, not the admissibility of his testimony. Moreover, Mizell’s opinions are of consequence, and based on the Defense’s damages theory, they tend to make it more likely than not that something other than Koster’s conduct caused Riles’ health complications. Accordingly, Mizell’s causation opinions are neither irrelevant nor unfairly prejudicial. The Court will not limit Mizell’s testimony on this basis.

Riles also sought to exclude Mizell’s opinions that reference comments by “Plaintiff’s counsel,” claiming such opinions are irrelevant and unreliable. Koster responded that Mizell is actually referring to statements made by Rehnke. Such references to “Plaintiff’s counsel” in Mizell’s report are confusing. However, given that the statements in Mizell’s report that mention Riles’ counsel do appear to be referring to statements in Rehnke’s report, the Court refused to exclude Mizell’s opinions on this basis.

Additionally, Riles appeared concerned that Mizell will present new or additional opinions beyond those in his report. Riles argued that Rule 26 of the Federal Rules of Civil Procedure limits Mizell’s testimony to the “four corners of his report.”

Because parties have an ongoing duty to supplement their expert witnesses’ reports, the Court will not preemptively limit Mizell’s testimony on this basis.

Riles also seeks to prohibit Mizell from testifying to any opinions that mention Rehnke, which Riles seems to label as rebuttal opinions. Riles argued that Mizell should be prohibited from providing rebuttal testimony because Koster was required to disclose any rebuttal opinions that Mizell will offer and failed to do so. However, Koster’s decision not to identify a rebuttal expert does not mean that Mizell’s testimony should be limited.

Further, Riles argued that Mizell should not be allowed to testify about any opinions that mention Rehnke because Mizell did not list Rehnke’s report among the documents that he reviewed when preparing his own report. Mizell’s failure to list Rehnke’s report initially confuses the reader because Mizell’s report clearly indicates that he reviewed Rehnke’s opinions. Koster explains that the failure to list Rehnke’s report was an “oversight.” This oversight is not a reason to exclude Mizell’s report.

Lastly, Riles claimed that portions of Mizell’s testimony that mention Rehnke are irrelevant. His opinions that mention Rehnke dispute the appropriate treatment for Riles and the likelihood that his catheter will continue to intermittently leak.

Therefore, the Court denied the Plaintiff’s motion in limine to limit the testimony of Mizell

Held

The Court granted in part, denied in part, and deferred in part Defendant's motion to exclude the Testimony of Mark McKinnon; denied the Defendant's motion to exclude the testimony of Dr.Ernest Rehnke; and denied the Plaintiff's motion in limine to limit the testimony of Dr. Jason Mizell.

Key Takeaway

A disagreement between the parties’ experts does not render one expert’s opinions irrelevant.

Disclaimer: Please note that Dr. Ernest Rehnke passed away on September 21, 2026. This article was written based on court records and reflects information available at the time of the proceedings.

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