Police-practices experts occupy an unusual position in federal civil-rights litigation. Their testimony is generally not based on laboratory experiments, statistical models, epidemiological studies, or the other methodologies commonly associated with Daubert litigation. Instead, police-practices experts frequently rely on years of law-enforcement experience, training, supervision, agency policies, professional standards, published materials, and experience reviewing officer conduct.
None of that became inadmissible on December 1, 2023.
But Federal Rule of Evidence 702 did change in a way that should matter to every lawyer who retains, prepares, defends, or challenges a police-practices expert.
The amended rule expressly requires the proponent to demonstrate to the court that it is more likely than not that Rule 702’s admissibility requirements are satisfied. It also requires that the expert’s opinion reflect a reliable application of the expert’s principles and methods to the facts of the case.1
Experience can be the foundation for expert testimony. Experience, standing alone, is not the analysis.
Shield PSTA police-practices expert who identifies a professional standard, explains where that standard comes from, identifies the facts material to its application, and demonstrates how the standard produces the particular opinion offered remains on solid Rule 702 ground.
The expert who effectively says, “I have thirty years of experience, I reviewed the evidence, and this violated generally accepted police practices,” presents a much more substantial admissibility problem.
What Actually Changed in 2023
Rule 702 now provides that a qualified expert may testify if the proponent demonstrates to the court that it is more likely than not that:
(a) the expert’s scientific, technical, or other specialized knowledge will help the trier of fact;
(b) the testimony is based on sufficient facts or data;
(c) the testimony is the product of reliable principles and methods; and
(d) the expert’s opinion reflects a reliable application of the principles and methods to the facts of the case.2
The 2023 amendment was not intended to overturn Daubert, General Electric Co. v. Joiner, or Kumho Tire Co. v. Carmichael. Nor did it newly invent the proposition that admissibility must be established by a preponderance of the evidence. Rule 104(a) already imposed that standard.
The amendment instead made the allocation of responsibility unmistakable.
The Advisory Committee specifically addressed decisions holding that questions concerning “the sufficiency of an expert’s basis” and “the application of the expert’s methodology” were matters of weight for the jury rather than admissibility for the judge. The Committee characterized those decisions as incorrect applications of Rules 702 and 104(a).3
That clarification matters enormously in police-practices cases because many challenges to these experts concern precisely those two subjects: What is the basis for the claimed police standard? And how was that standard reliably applied to what occurred here?
The Ninth Circuit’s published decision in Engilis v. Monsanto Co. reinforces the point. Although Engilis was a toxic-tort case rather than a police case, the court rejected any categorical preference favoring admission of expert testimony and emphasized the trial court’s gatekeeping obligation. The reliability inquiry may include examination of the expert’s reasoning process—not merely whether the expert can identify some generally accepted methodology.4
The Fifth Circuit has similarly applied the amended rule to affirm exclusion where an expert failed to disclose a reliable method of selecting data and attempted to draw broad conclusions from an inadequate factual basis.5
Police-practices experts operate under the same Rule 702.
Qualification and Reliability Are Different Questions
One of the most important distinctions for police-expert litigation is between being qualified and having reached the particular opinion reliably.
A thirty-year police veteran may readily qualify to testify about some aspects of police work. That does not establish that every opinion offered by that witness is reliable.
The Ninth Circuit articulated this distinction even before the amendment in United States v. Holguin: courts must distinguish an expert’s qualifications from the reliability of the expert’s principles and methods.6 Post-amendment district courts are increasingly applying that principle to police-practices testimony.
The CV Is Not the Methodology
- A résumé answers: Why should this person possess specialized knowledge?
- Rule 702(c) and (d) ask: What reliable professional principle or method produced this opinion, and how was it applied?
- The practical mistake: Treating years of service as though they independently establish the reliability of every opinion offered.
Avery and Rehn: The Analytical Gap Becomes an Admissibility Problem
Two Western District of Washington decisions provide unusually clear examples.
In Avery v. City of Seattle, a police expert opined, among other things, that officers acted inconsistently with police training, practices, and procedures. The court excluded challenged opinions where the expert reached that conclusion without identifying the training, practice, or procedure that required officers to act differently.7
The problem was not that experience-based police testimony is categorically unreliable. The problem was the missing analytical bridge.
The same issue arose even more directly in Rehn v. City of Seattle. There, plaintiff’s police-practices expert, Sue Peters, offered opinions that Seattle officers failed to take necessary investigative steps to verify an address and failed to follow “basic police practices of address verification.”
The district court excluded her testimony.
The report did not explain what constituted the necessary investigative steps, what “basic practices” required, how the expert’s law-enforcement experience established those practices, or how the officers’ conduct compared with them. A statement that the conclusions were based on the expert’s training, experience, and review of the discovery was insufficient.8
The court later denied reconsideration, emphasizing that an experience-based expert remains subject to a reliability inquiry and that the court may consider whether experience actually supports the conclusion and whether the reasoning has been adequately explained.9
Compare the Two Approaches
Vulnerable: “Based on my training and experience, the officers violated basic police practices.”
Stronger: Identify the training principle; explain how experience and recognized sources establish it; identify the facts that matter; then show why application of that principle to those facts supports the conclusion.
An important limitation should be noted. Rehn subsequently reached the Ninth Circuit, but the appeal addressed qualified immunity, not the exclusion of Peters. The Ninth Circuit therefore did not affirm or otherwise endorse the Rule 702 ruling on appeal.10 The district court decision remains persuasive—not circuit—authority.
Villanueva-Galvez: Citing Standards Is Not Enough if the Opinion Is Not Connected to Them
A 2026 Northern District of California decision makes the same point in a police-canine case.
In Villanueva-Galvez v. City of San Jose, plaintiff retained Ernest Burwell as a police-practices expert in litigation arising from a canine deployment. The court recognized the general proposition that an expert may testify about police standards and best practices and whether an officer complied with them.
But the court excluded the challenged opinions.
For example, Burwell proposed to testify categorically that the canine was not properly trained. His report quoted provisions from the San Jose Police Department manual, but the challenged conclusion was not adequately tied to those standards or otherwise explained.11
That is a subtle but significant point. A report cannot solve the Rule 702 problem simply by placing several pages of policies, standards, or training materials in one section and several pages of conclusions in another. The expert must connect them.
The court must be able to see: Standard → material facts → application → conclusion.
Post-2023 Rule 702 analysisPolice-Practices Expertise Is Not Universal Police Expertise
The amendment also makes careful definition of the expert’s actual field increasingly important.
“Police practices” is not one unlimited discipline.
A witness with substantial patrol and use-of-force experience may have little specialized knowledge concerning canine training, SWAT tactics, firearms instruction, accident reconstruction, jail classification, internal-affairs investigations, digital forensics, crowd management, crisis negotiation, biomechanics, human factors, or reaction-time science.
Davis v. City of Covington illustrates the distinction.
The Eastern District of Kentucky accepted Michael Lyman as qualified concerning general use-of-force principles but held that his expertise did not extend automatically to specialized police-canine training, handling, practices, or tactics. The court allowed him to discuss general use-of-force concepts, including where canine deployment may fall within a force continuum, while restricting specialized canine testimony for which the necessary foundation had not been established.12
The important principle is that qualification should be considered opinion by opinion, not simply witness by witness.
Not: “Is this person a police expert?”
But: “Is this person qualified by knowledge, skill, experience, training, or education to give this particular opinion?”
Experience Can Still Be a Reliable Methodology
None of this means that police experts must convert professional judgment into laboratory science.
Kumho Tire expressly rejected a science-only conception of expert testimony. Rule 702 applies to “scientific, technical, or other specialized knowledge.”13
Several recent police-practices decisions properly preserve that principle.
In Atchison v. City of Tulsa, the defendants challenged police-practices expert Joseph Allio, arguing in part that his opinions lacked a reliable methodology.
The Northern District of Oklahoma acknowledged that Rule 702 terminology can fit nonscientific professional expertise imperfectly. But it did not exempt Allio from reliability review.
Instead, the court examined what he actually did. Allio reviewed depositions, transcripts, police reports, recorded interviews, affidavits, police manuals, criminal-investigation source material, and academic sources. He then explained that he applied his training, education, experience, and knowledge of police procedure and investigative practices to those materials.
The court permitted the testimony.14
That decision identifies the proper middle ground. Experience itself can supply specialized knowledge. But the expert should explain how that experience functions as a method of analysis in the particular case.
Similarly, in Asante-Chioke v. Dowdle, the Eastern District of Louisiana rejected an argument that a police use-of-force expert’s methodology was unreliable simply because it rested on technical or specialized knowledge rather than scientific testing. The court allowed appropriate police-practices testimony while barring the expert from giving the legal conclusion that the officers’ actions were objectively unreasonable.15
In a later ruling involving a defense police expert in the same litigation, the court again held that experience and specialized knowledge concerning police training and procedures could provide a reliable basis for testimony. But the court separately excluded proposed opinions in areas—such as mental health and human perception/reaction time—for which the expert lacked the necessary qualifications.16
Thus, the post-amendment rule is not experience is insufficient. It is experience must be connected to the opinion.
The “Force Science” Problem: Match the Foundation to the Proposition
Use-of-force experts present an additional problem when they move from professional practices into scientific propositions.
In Tovar v. City of San Jose, a police expert proposed testimony involving reaction time, cognition, video evidence, and what was characterized as scientific analysis. The Northern District of California distinguished legitimate police training and practices testimony from scientific opinions for which the witness lacked the appropriate scientific qualifications and foundation. The court limited the expert accordingly.17
That does not mean reaction-time testimony is categorically inadmissible.
Richardson v. United States illustrates the opposite result. There, the Western District of Missouri permitted a police expert to offer reaction-time testimony where his qualifications and report supplied a materially stronger foundation. The expert had decades of police experience, specialized certifications, experience with the Force Science Institute, had conducted reaction-time research, cited his own publications, and relied on numerous other published studies.18
Likewise, in Zuniga v. City of Los Angeles, the Central District of California declined to exclude police-practices expert Edward Flosi based merely on references to “force science” materials where the opinions actually offered were grounded in his extensive law-enforcement background and police practices and tactics rather than the challenged scientific propositions.19
The lesson is not to embrace or reject “force science” by label. The Rule 702 question is more precise: What proposition is the expert actually offering, and does the witness possess a reliable foundation for that proposition?
Experts Still Cannot Decide the Law
A separate line remains largely unchanged by the 2023 amendment: police experts may assist the jury with professional practices, but they generally may not instruct the jury how constitutional or statutory law applies.
Police-practices testimony may properly address accepted investigative procedures, officer training, policy requirements, use-of-force options, supervisory practices, professional standards, and whether conduct was consistent with an identified training or professional standard.
But experts generally should not be permitted simply to announce that an officer used “excessive force” within the meaning of the Fourth Amendment; an arrest lacked “probable cause”; conduct was “objectively unreasonable” as a constitutional matter; an officer violated the Constitution; or a municipality satisfied the legal requirements for Monell liability.
Davis, Jordan, and Asante-Chioke all illustrate variants of this distinction.20
In Jordan v. Town of Fairmount Heights, for example, the District of Maryland found that Gregory Gilbertson’s education, police-practices background, teaching, and use-of-force expertise could assist the jury in evaluating the significance of prior officer conduct relevant to hiring and retention. But the court barred him from telling the jury that the defendant police chief was negligent or reckless or had breached the governing standard of care.21
The professional standard can be the subject of expertise. The governing legal conclusion ordinarily belongs to the court and factfinder.
“Weight, Not Admissibility” Still Exists—After the Threshold Is Met
The 2023 amendment did not abolish cross-examination. Nor does every factual disagreement justify excluding an expert.
The Advisory Committee itself explained that once a court finds the expert has a sufficient basis, the fact that the expert did not review every conceivable study or item of information may properly concern weight rather than admissibility.22
The sequence matters.
First, the court asks whether the proponent has demonstrated that Rule 702 is satisfied. Only then does ordinary adversarial testing take over.
A Strong Police-Practices Opinion Should Show
- Qualification: expertise in the particular discipline at issue.
- Standard: the professional principle being applied.
- Foundation: a reliable basis for that standard.
- Facts: sufficient case-specific facts or data.
- Application: an explained analytical bridge from the standard and facts to the opinion.
- Limits: a conclusion no broader than the methodology supports.
Opposing counsel may still argue that the expert misunderstood a video, overlooked a witness statement, selected the wrong policy, gave excessive weight to one fact, or should have reached another conclusion. Those may well be classic cross-examination issues.
The problem arises when “weight, not admissibility” is invoked before the analytical foundation itself has been established.
What a Police-Practices Report Should Do Differently
A post-2023 police-practices report should allow the judge to reconstruct the reasoning process. For each significant opinion, the report should answer seven questions.
1. What is the expert’s actual field?
Define it with precision. “Police practices” may be too broad. “Police use-of-force training and tactical decision-making” is more useful.
2. What professional principle is being applied?
State the practice, training principle, policy requirement, or professional standard.
3. Why is that principle reliable?
Identify its source. Depending upon the opinion, relevant sources might include agency policy, state POST materials, accepted professional training, national standards, published literature, research, historical professional practice, or sufficiently extensive specialized experience.
4. What facts matter?
Identify the case-specific facts upon which the opinion actually depends.
5. How was the principle applied?
This is the analytical bridge. Explain why those facts, evaluated under the identified professional principle, support the conclusion.
6. What assumptions or factual disputes exist?
An expert need not decide disputed facts. An opinion can properly be conditional: “If the jury determines X occurred, then accepted police practice would require Y.”
7. How far does the conclusion legitimately go?
Do not turn a professional-practices opinion into a constitutional conclusion, and do not turn practical police experience into scientific expertise that the witness does not possess.
The Deposition Strategy Should Change Too
For lawyers challenging police experts, the amended Rule 702 inquiry suggests a more productive deposition than simply attacking credentials.
The critical questions are analytical:
- What precise professional standard are you applying?
- Where does that standard come from?
- Is it written anywhere?
- How do you know it is generally accepted?
- Is that an agency-specific practice or a national practice?
- What facts are essential to your conclusion?
- What happens to your opinion if that fact is disputed?
- What contrary information did you consider?
- What is the method by which you moved from your experience to this conclusion?
- What separates the standard you identify from your own personal preference?
- Can another qualified police expert reproduce your reasoning?
- Which portion of your opinion is based upon police expertise and which portion depends upon scientific literature?
- Are you applying specialized knowledge, or simply telling the jury what you believe the body-worn-camera video shows?
Those questions now track the text of Rule 702 far more closely than a generalized attack on whether the expert has enough years in policing.
Conclusion
The 2023 amendment did not end experience-based police-practices testimony.
It did something more subtle.
It placed renewed emphasis on the part of the expert’s analysis that too often remained implicit.
A career in law enforcement may explain why the witness possesses specialized knowledge. It does not necessarily explain why a particular opinion is reliable.
The Expert Should Be Able to Demonstrate
- This is the professional principle.
- This is why I am qualified to identify and apply it.
- This is the reliable basis for the principle.
- These are the facts that matter.
- This is how I applied the principle to those facts.
- This is the conclusion that process supports.
For lawyers retaining police-practices experts, that analysis should occur while the report is being prepared—not after a Rule 702 motion is filed.
For lawyers challenging those experts, the amended rule provides an equally clear roadmap.
The question is no longer satisfied by asking whether the expert has enough experience to have an opinion.
The more important question is: Has the expert shown the court how that experience reliably produces this opinion?
Footnotes
- Fed. R. Evid. 702(b)–(d); Fed. R. Evid. 702 advisory committee’s note to 2023 amendment.
- Fed. R. Evid. 702.
- Fed. R. Evid. 702 advisory committee’s note to 2023 amendment (explaining that rulings treating sufficiency of basis and application of methodology as categorically matters of weight rather than admissibility incorrectly applied Rules 702 and 104(a)).
- Engilis v. Monsanto Co., 151 F.4th 1040, 1046–50 (9th Cir. 2025).
- Nairne v. Landry, No. 24-30115, slip op. at 36–39 (5th Cir. Aug. 14, 2025) (affirming exclusion where the expert failed to disclose a reliable method for data selection, relied on insufficient data, and did not reliably apply his methodology).
- United States v. Holguin, 51 F.4th 841, 854–55 (9th Cir. 2022).
- Avery v. City of Seattle, No. 2:22-cv-00560-LK, 2024 WL 2959541, at *6–7 (W.D. Wash. June 12, 2024).
- Rehn v. City of Seattle, No. 2:23-cv-01609-RAJ, Dkt. 56, at 5–8 (W.D. Wash. July 1, 2025).
- Rehn v. City of Seattle, No. 2:23-cv-01609-RAJ, Dkt. 71, at 2–5 (W.D. Wash. Oct. 28, 2025) (denying reconsideration of expert exclusion).
- Rehn v. City of Seattle, No. 25-4844, mem. disp. at 1–5 (9th Cir. June 18, 2026) (reversing denial of qualified immunity without addressing the district court’s Rule 702 ruling). The memorandum disposition is unpublished and nonprecedential except as permitted by Ninth Circuit Rule 36-3.
- Villanueva-Galvez v. City of San Jose, No. 5:24-cv-09055-VKD, Dkt. 71, at 8–10 (N.D. Cal. June 4, 2026).
- Davis v. City of Covington, No. 2:23-cv-00066-DCR, Dkt. 52, at 18–26 (E.D. Ky. May 13, 2024).
- Kumho Tire Co. v. Carmichael, 526 U.S. 137, 147–49, 156 (1999).
- Atchison v. City of Tulsa, No. 4:21-cv-00286-JDR-SH, Dkt. 222, at 4–9 (N.D. Okla. Jan. 6, 2026).
- Asante-Chioke v. Dowdle, No. 2:22-cv-04587-CJB-EJD, Dkt. 239, at 12–17 (E.D. La. Oct. 2, 2025).
- Asante-Chioke v. Dowdle, No. 2:22-cv-04587-CJB-EJD, Dkt. 249, at 8–12 (E.D. La. Dec. 12, 2025).
- Tovar v. City of San Jose, No. 5:21-cv-02497-EJD, Dkt. 89 (N.D. Cal. Sept. 24, 2024).
- Richardson v. United States, No. 6:23-cv-03337-RK, Dkt. 169, at 8–10 (W.D. Mo. Mar. 2, 2026).
- Zuniga v. City of Los Angeles, No. 2:22-cv-03665-CBM-AS, 2024 WL 4744370, at *2 (C.D. Cal. Oct. 7, 2024).
- See, e.g., Davis, Dkt. 52, at 20–26; Asante-Chioke, Dkt. 239, at 11–13; Jordan v. Town of Fairmount Heights, No. 8:22-cv-02680-AAQ, 2024 WL 732011, at *3–5 (D. Md. Feb. 21, 2024).
- Jordan, 2024 WL 732011, at *3–5.
- Fed. R. Evid. 702 advisory committee’s note to 2023 amendment. See also Bolder v. Brecker, No. 5:23-cv-05138-JMG, Dkt. 77, at 23 (E.D. Pa. Oct. 31, 2025).
This article surveys significant publicly retrievable federal decisions addressing police-practices and closely related experience-based expert testimony after the December 1, 2023 amendment to Rule 702, together with appellate decisions interpreting the amended rule. It does not represent that every PACER-only or unindexed district-court order nationwide has been identified.
