--- title: "Law Enforcement Expert Witness’ Testimony on Certain Customs and Practices Excluded" meta: "og:description": "Expert testimony on acceptable law enforcement standards limited" "og:title": "Law Enforcement Expert Witness’ Testimony on Certain Customs and Practices Excluded" author: "Expert Witness Profiler" description: "Expert testimony on acceptable law enforcement standards limited" --- # Law Enforcement Expert Witness’ Testimony on Certain Customs and Practices Excluded Posted on July 9, 2024 by Expert Witness Profiler This civil rights action arises out of an October 23, 2020 traffic stop involving Plaintiff, Kary Jarvis and Daytona Beach Police Department officers Marville Tucker and James Mackenzie. As a result of the traffic stop, Plaintiff was injured and filed a complaint alleging false arrest. Defendants, City of Daytona Beach as well as Marville Tucker and James Mackenzie filed respective _[Daubert](https://www.law.cornell.edu/wex/daubert_standard)_motions to exclude the testimony of Plaintiff’s expert [Thomas Tiderington](https://expertwitnessprofiler.com/expert-witness/Thomas-Tiderington/1552463). Tiderington opined that the Daytona Beach Police Department has consistently demonstrated a custom and practice of inadequately supervising, training, and disciplining its personnel. ## **Law Enforcement Expert Witness** [Thomas J. Tiderington](https://expertwitnessprofiler.com/expert-witness/Thomas-Tiderington/1552463) has served as a full-time law enforcement officer with three different police departments and as a Group Supervisor for the United States Drug Enforcement Administration’s South Florida Regional Task Force. He has trained over 10,000 federal, state, and local law enforcement officers on police practices and criminal investigations. [Want to know more about the challenges Thomas Tiderington has faced? Get the full details with our Challenge Study report.](https://app.expertwitnessprofiler.com/login?eId=1552463) ## **Discussion by the Court** #### **Opinion One** Tiderington stated that Defendants’ actions were unreasonable, unjustifiable, and deviated from acceptable law enforcement standards. Defendants Marville Tucker and James Mackenzie argued that Tiderington’s opinion should be excluded because it is a legal conclusion and will mislead the jury. The Court held that Defendants’ motion to exclude opinion one was granted to the extent that Tiderington may not opine that Defendants’ application of force was unreasonable or unjustifiable. Defendants’ motion was otherwise denied as to opinion one. #### **Opinion Two** Tiderington stated that the Daytona Beach Police Department has a custom and practice of inadequately supervising, training, and disciplining its personnel and but for this pattern Plaintiff would not have been detained and incarcerated. Defendants Marville Tucker and James Mackenzie argued that Tiderington’s opinion should be excluded because it is a legal conclusion that encroaches on the purview of the jury. The Court held that Tiderington’s report discussed his experience but failed to establish “_how_ that experience led to the conclusion reached, why that experience is a sufficient basis for the opinion, and how that experience is reliably applied to the facts.” Opinion two discussed the custom, practice, and patterns of the Daytona Beach Police Department, but the report only cited one example beyond the present case. Tiderington confirmed this limited basis for the opinion in his deposition. The Court excluded Tiderington’s opinion two as unreliable because it lacked a reasoned analysis supported by data, identified standards, or comparison with practices in other sheriff’s offices. ## **Held** Defendant, City of Daytona Beach’s, motion to exclude expert opinions of Thomas Tiderington was fully granted by the Court. However, the Court granted in part Defendant Marville Tucker and Defendant James Mackenzie’s motion to exclude certain opinions of Tiderington. ## **Key Takeaway:** Tiderington’s opinion concluding that Defendants’ application of force was unreasonable or unjustifiable was excluded as to opinion one since it is a legal conclusion and could mislead the jury. Tiderington’s opinion in opinion two concerning Defendant’s custom and practice was also excluded because it lacked a reasoned analysis supported by data, identified standards, or comparison with practices in other sheriff’s offices. ## **Case Details:** --- ## **You Might Also Like** ![Animal Behavior Expert Was Not Allowed to Opine on Drug Detection Dogs](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-07T175803.497.jpg) [**Animal Behavior Expert Was Not Allowed to Opine on Drug Detection Dogs**](https://expertwitnessprofiler.com/law-enforcement-expert-witness-testimony-on-certain-customs-and-practices-excluded/animal-behavior-expert-was-not-allowed-to-opine-on-drug-detection-dogs)![Law Enforcement Expert Was Not Allowed to Opine on the Suspect's Flight](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-07T131602.639.jpg) [**Law Enforcement Expert Was Not Allowed to Opine on the Suspect’s Flight**](https://expertwitnessprofiler.com/law-enforcement-expert-witness-testimony-on-certain-customs-and-practices-excluded/law-enforcement-expert-was-not-allowed-to-opine-on-the-suspects-flight)![Industrial Hygiene Expert's Testimony on Environmental Exposure Limited](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-06T194531.503.jpg) [**Industrial Hygiene Expert’s Testimony on Environmental Exposure Limited**](https://expertwitnessprofiler.com/law-enforcement-expert-witness-testimony-on-certain-customs-and-practices-excluded/industrial-hygiene-experts-testimony-on-environmental-exposure-limited)![Psychology Expert's Testimony on Grooming Limited](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-06T164223.328.jpg) [**Psychology Expert’s Testimony on Grooming Limited**](https://expertwitnessprofiler.com/law-enforcement-expert-witness-testimony-on-certain-customs-and-practices-excluded/psychology-experts-testimony-on-grooming-limited)![Mechanical Engineering Expert Allowed to Opine on the Behavior of Wheelchairs](https://ewp-blog.expertwitnessprofiler.org/wp-content/uploads/2026/04/blog-pic-640X480-2026-04-03T203819.018.jpg) [**Mechanical Engineering Expert Allowed to Opine on the Behavior of Wheelchairs**](https://expertwitnessprofiler.com/law-enforcement-expert-witness-testimony-on-certain-customs-and-practices-excluded/mechanical-engineering-expert-allowed-to-opine-on-the-behavior-of-wheelchairs)