Expert Witness Profiler

Category: Law Enforcement Expert Witness

  • Law Enforcement Expert Was Allowed to Opine on Ride-Along Policies

    Law Enforcement Expert Was Allowed to Opine on Ride-Along Policies

    Zailey Hess sued former Hammond police officer Jamie Garcia, alleging that he sexually assaulted and harassed her during a ride-along for her criminal justice class in violation of the Fourteenth Amendment’s Equal Protection and Due Process Clauses.

    Garcia filed a motion to exclude the testimony of Hess’ expert witness, Dan Kender.

    Law Enforcement Expert Witness

    Daniel R. Kender worked as a Hammond police officer for 28 years, including as a patrol officer, evidence technician, traffic crash investigator, accident reconstructionist, field training officer (including educating ride-along participants), law enforcement instructor, and police sergeant.

    Over that time, he participated in various law enforcement training. He holds a bachelor’s degree in computer information systems and a master’s degree in cybersecurity and digital forensics. Kender is an assistant professor of computer science, though he has worked privately in crash reconstruction since 2000—first for another business, and for himself since 2008.

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

    Discussion by the Court

    Garcia asked the Court to exclude all of Kender’s prospective testimony, arguing that he (1) may not testify to a witness’ credibility, (2) isn’t needed or qualified to testify on whether Garcia’s ride-along conduct was inappropriate based on Hammond’s policies or a seatbelt’s functionality, and (3) isn’t qualified to testify on sexual grooming or the behavior of a victim of sexual assault or harassment.

    A. Opinion on the Believability of Hess’ Accusations

    Kender reviewed Hess’ recollections of their ride-alongs with Garcia and opined that her accusations appeared genuine because fabricated accounts tend to be more exaggerated, while Garcia’s recollections struck him as inconsistent.

    Garcia said that Kender lacked the requisite qualifications in psychology or human behavior to reach this opinion and added that his credibility opinion cannot help the jury.

    The latter is what prevents him from being an expert here. Qualifications aside, and those remain in doubt, an opinion witness cannot sift through the testimony of others, tell the jury whom to believe, or otherwise argue the implication of seeming inconsistencies. The jury alone performs the job of assessing the credibility of witnesses, and it needs no help. Kender acknowledged that this takes no expertise beyond the common sense of each juror.

    B. Opinions on the Propriety of Garcia’s Conduct under Hammond Police Department Ride-Along Policies and Training

    Kender’s report described the purposes and procedures of a ride-along with the Hammond Police Department. He described the ride-along program as fostering positive police-community relations and educating the public on police functions.

    Based on his prior work as a field training officer and experience leading educational ride-alongs, he opined about the training Hammond law enforcement officers receive and the objectives they acknowledge to guide their ride-alongs with members of the public.

    Jurors may have early impressions about ride-alongs, or either heard of them or even participated in one, and perhaps have early impressions about their goals for both the public and police agency; but Kender would offer something specialized to understand their dynamics, objectives, and the training that goes into making sure that police officers handle them safely. He has the credentials to speak to these issues, and his method of offering these opinions grows out of his training, his training of others, and the policies in place at the Hammond Police Department.

    Beyond this scope of testimony and the context it provides the jury, the jury truly needs no help. Nor is there anything particularly expert about anything else.

    C. Opinions on the Behavior of a Victim of Sexual Misconduct and on Sexual Grooming Behavior

    Kender sought to opine that Hess’ account of Garcia’s ride-along conduct was consistent with sexual grooming by predatory child molesters. He stated that he based this opinion on his training and experience as a police officer, his review of the record, and a 2017 article about grooming behaviors by predatory child molesters.

    Garcia argued that Kender lacked the necessary qualifications to testify about grooming behavior or a victim’s common reactions to sexual assault. He said that Kender merely read transcripts rather than interviewing or observing any witnesses, and that his opinion lacked a scientific method.

    Analysis

    Kender worked as a police officer for 28 years. His curriculum vitae reflects fairly standard training at the Indiana Law Enforcement Academy and at the Northwest Indiana Law Enforcement Training Center, and it seems over the years he developed particular focuses in crash investigation, forensics (including computer forensics), and training of officers. None of this screams out expertise in sexual grooming. That said, he testified that he worked traffic part of the time, but also worked patrol involving cases of child molesting, sexual battery, and rape. He received some training on sexual grooming at the academy, and he later served as a field training officer and evidence technician when he “handled a lot more of [these] cases then.”

    While Kender hasn’t specialized professionally in sex crimes or psychology, the Court held that he may speak to patterns of sexual grooming insofar as his training and experience take him.

    Garcia also criticized Kender’s method, except that Kender outlines specific signs or dynamics of sexual grooming (something well beyond his say-so); and he thereby provided a roadmap for his application of these and his decision-making toward an opinion, and decision-making not unlike what law enforcement officers often would make in the field.

    Aspects of grooming may be intuitive to some jurors, and jurors will need no help understanding that much of the alleged behavior would be not just unprofessional but unreasonable by a police officer to commit; but other aspects about grooming or a victim’s sometimes-less-than-intuitive reactions to sexual assault will be invariably foreign to them, so this opinion about grooming will aid in their understanding of its markers and the constitutional impropriety of such behavior during a ride-along.

    Held

    The Court granted in part and denied in part Jamie Garcia’s motion to exclude Daniel Kender’s opinions.

    Key Takeaway

    Kender offered something by way of specialized knowledge to understand the objectives and training associated specifically with ride-alongs. The jury gets to decide whether Garcia’s conduct violated the Constitution with the aid of that context, but without need of more.

    For instance, jurors understand driving safety and the importance of having two hands on a steering wheel (or not). Jurors can assess whether physical contact or sexualized conversations between an officer and minor passenger (or with a sex worker) are discriminatory rather than serve any legitimate government objective.

    Case Details:

    Case Caption: Hess V. Garcia
    Docket Number: 3:21cv101
    Court Name: United States District Court, Indiana Northern
    Order Date: March 13, 2026
  • Law Enforcement Expert Allowed to Opine on the Dynamics of Consensual Adult Sex Work

    Law Enforcement Expert Allowed to Opine on the Dynamics of Consensual Adult Sex Work

    Defendants Brandon Washington and Maria Georgianna Palm are charged with various crimes arising out of their scheme to recruit, entice, harbor, transport, provide, obtain, and maintain vulnerable women, and to perform commercial sex acts for their financial benefit via threats of force, fraud, and coercion.

    The government retained FBI Supervisory Special Agent Steven Vienneau to testify at trial about the commercial sex industry and the commercialized sexual exploitation of victims by individuals who manipulate, coerce, entice, persuade, and control individuals to participate in prostitution.

    The Defendants contended that the agent is unqualified to opine on adult consensual sex work dynamics in cases involving adult women. They argued that his professional background is “overwhelmingly” rooted in child exploitation and juvenile sex trafficking. Defendants also contended that his proposed testimony fails Fed. R. Evid. 702 reliability requirements. And last, Defendants asked the Court to exclude the testimony under Fed. R. Evid. 403 suggesting the risk of unfair prejudice given the testimony invokes emotionally charged concepts.

    Law Enforcement Expert Witness

    Steven Vienneau has been a Special Agent with the FBI since 2003. He supervised the squad responsible for investigating crimes against children and human trafficking including abductions homicides sexual abuse sex trafficking labor trafficking enticement child pornography and online sexual exploitation of children. He also provided training to local state federal and international law enforcement partners in conducting investigation into these matters.

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

    Discussion by the Court

    The essence of the testimony of Vienneau is to provide expert testimony about the pimp-prostitute relationship and subculture. According to the Court, such evidence will assist the jury in assessing the veracity of witness testimony who may be testifying about relationships between pimps and prostitutes. It will also assist the jury in understanding the subculture of the sex trafficking industry.

    The Defendant’s allegation that the agent lacks qualifications to provide expert testimony on adult sex trafficking fails to consider the extent and depth of his experience. His experience is not limited to only minors. As explained in his disclosure, since 2004 his experience has been involved in human trafficking involving both adults and minors. His qualifications involve interviewing over 200 females involved in commercial sex, including approximately 125 adults and 75 minors. Based upon the Government submissions, Vienneau is qualified to testify as an expert on the topic of sex trafficking subculture of adults due to his knowledge, experience, training and education.

    The Defendants contended that Vienneau did not meet the reliability requirement of Rule 702. The Government disclosures belie the Defendant’s assertions. The disclosures demonstrate the agent has gained his expertise through 20 years as an FBI Special Agent specializing in sex trafficking crimes. He also has honed this expertise through hundreds of hours of training and participated in over 100 investigations of sex trafficking offenses, personal interviews with over 200 victims and potential victims of sex trafficking regarding their experience with prostitution and conducted personal interviews with approximately 20 suspected traffickers.

    Held

    The Court denied the Defendant’s motion to exclude the testimony of Government’s expert Steven Vienneau.

    Key Takeaway

    Expert testimony on “the relationship between prostitutes and pimps” is relevant in a sex trafficking case as it can assist the jury in understanding a relationship which is not the subject of common knowledge of jurors.

    The probative value of the agent’s testimony is great, and it goes to assisting the jury in understanding the witness’s testimony and help assess the credibility of the victims and witnesses in this case. Any risk of unfair prejudice is greatly outweighed by the probative value of the proposed evidence.

    Case Details:

    Case Caption: United States V. Washington
    Docket Number: 2:23cr58
    Court Name: United States District Court, Washington Western
    Order Date: February 02, 2026
  • Law Enforcement Expert Was Allowed to Opine on the Deputies’ Conduct

    Law Enforcement Expert Was Allowed to Opine on the Deputies’ Conduct

    On May 21, 2022, Defendants Deputies Montana Arceo and Brandon Avalos contacted Mr. Lyric Leeyn Cline at an ARCO gas station in Tacoma, Washington, after observing a vehicle they believed matched one involved in recent criminal incidents.

    Cline fled on foot, the deputies pursued him, and a struggle followed during which the deputies used physical force, including strikes, before other officers arrived and Cline was handcuffed and transported for medical evaluation.

    Cline brought claims for excessive force against Deputies Arceo and Avalos and for failure to intercede against Deputy Avalos.

    Defendants retained Mr. Chris M. Nielsen, a retired SWAT officer and police trainer, to offer opinions on police practices and use-of-force. In general, Nielsen opined that the decision to contact and pursue Cline, the types and levels of force used, and the provision of medical care were consistent with generally accepted police training and Pierce County Sheriff’s Department policies.

    Law Enforcement Expert Witness

    Chris M. Nielsen has approximately thirty-one thousand hours of training and operational experience in patrol-level operations, tactics, supervisory, instructional, and leadership experience. He retired from active law enforcement in December, 2024.

    He has an Associate of Arts degree from Bellevue College, a Bachelor of Arts in psychology from the University of Washington (cum laude, Phi Beta Kappa), a Master of Arts degree in political science from the Maxwell School of Citizenship and Public Affairs at Syracuse University and a Juris Doctor degree from the Syracuse University College of Law (cum laude).

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

    Discussion by the Court

    A. Reliability and Methodology

    Plaintiff challenged Nielsen’s methodology on the grounds that he relied on a limited factual record, did not review Avalos’s deposition before issuing his report or testifying, did not interview percipient witnesses, and did not supplement his opinions after additional discovery. Plaintiff cited portions of Avalos’s testimony and argued that those statements, together with the absence of certain videos from Nielsen’s review, undermine his conclusions.

    However, Nielsen reviewed department policies, training materials, reports, medical records, and video, and applied his law enforcement experience to assess the deputies’ conduct under generally accepted police standards and Pierce County policies. That is an accepted, experience-based methodology for police practices experts under Rule 702. 

    B. Use of Video Evidence

    Plaintiff argued that Nielsen’s testimony will not assist the jury because body-worn camera videos depict the encounter and that his descriptions of the footage risk confusing or misleading the jury.

    Defendants did not offer Nielsen as a video analyst. They offered him to explain police training, use-of-force frameworks, pursuit and Taser policies, and how officers are trained to assess flight, resistance, and threat. These subjects concern professional standards and decision-making processes outside typical juror experience and fall within Rule 702(a).

    The Court, however, enforced certain limits at trial. Nielsen may not narrate the videos or opine on purely factual questions such as where Cline’s hands were at a given moment or whether he in fact assumed a fighting stance. Jurors can reach those factual conclusions. He may testify about generally accepted police practices, relevant policies and training, how officers are taught to assess risk and select force options, and whether the deputies’ decisions were consistent with those standards, assuming specified facts.

    C. Legal Conclusions

    Plaintiff contended that Nielsen’s opinions that the deputies’ conduct was “necessary,” “appropriate,” and “consistent with training and policy” effectively stated that the force was objectively reasonable under the Fourth Amendment.

    Consistent with these principles, Nielsen may not testify that the deputies’ conduct was or was not objectively reasonable, constitutional, or similarly lawful. He may describe policies, training, and generally accepted police practices and state, in professional terms, whether particular actions were consistent with or departed from those standards, based on stated assumptions.

    D. Bias and Litigation History

    Plaintiff noted that Nielsen has testified exclusively for Law Enforcement Defendants in use-of-force cases and cites his compensation as evidence of bias and unreliability.

    However, the Court held that such matters may be explored on cross-examination and left to the jury in assessing what weight to give his testimony.

    Held

    The Court denied Plaintiff’s motion to exclude the testimony of Chris M. Nielsen.

    Key Takeaway

    Bias affects credibility and weight, not admissibility under Rule 702. Basically, Nielsen’s litigation history and compensation do not show that his methodology is unreliable or that his opinions lack a factual foundation. 

    Case Details:

    Case Caption: Cline V. Arceo
    Docket Number: 3:24cv5309
    Court Name: United States District Court, Washington Western
    Order Date: February 02, 2026
  • Law Enforcement Expert Was Allowed to Opine on Jail Policies

    Law Enforcement Expert Was Allowed to Opine on Jail Policies

    Billy Joe Altstatt, acting as the brother and legal guardian of Johnny Altstatt, an incapacitated individual, filed suit against the Board of County Commissioners of Oklahoma County and the Oklahoma County Criminal Justice Authority, alleging violations of Johnny’s federal and state constitutional rights.

    Defendants Board of County Commissioners for Oklahoma County and Oklahoma County Criminal Justice Authority each moved to strike Plaintiff’s expert witness, Phil Williams, on the grounds that Plaintiff failed to timely serve Williams’ expert report as required by Federal Rule of Civil Procedure 26(a).

    Law Enforcement Expert Witness

    Phil Williams is a retired police officer formerly assigned to the Oklahoma County Jail.

    His background, knowledge and expertise as to the operation of the jail, policies, personnel, and the manner of operations is of relevance.

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

    Discussion by the Court

    In support of its motion, Defendant Board of County Commissioners for Oklahoma County provided a timeline of events similar to the one set forth by the Court above. Further, Defendant asserted that it sent two emails to Plaintiff’s counsel-the first on April 8th and the second on April 10th- asking counsel for the missing expert witness report. Defendant Board contended that Plaintiff’s counsel did not respond to either email nor did they provide an expert report for Williams.

    Defendant Oklahoma County Criminal Justice Authority filed a motion to strike Williams as an expert witness for the same reasons set forth in Defendant Board of County Commissioners for Oklahoma County’s motion.

    Plaintiff essentially agreed with Defendants’ narrative of the timeline of events relating to his delay in filing his expert witness list and serving Williams’ expert witness report. Further, Plaintiff conceded that his “report is overdue and counsel have made mistakes since their attorney fell ill and had to withdraw from the representation of Plaintiff.” Plaintiff represented that Defendants have now been provided with Williams’ report and Plaintiff is “agreeable to providing Williams for deposition at a mutually agreeable date and time.”

    Although Plaintiff failed to timely serve Defendants with Williams’ expert report despite the Court granting him several extensions of time, the Court declined to impose the “drastic sanction” of striking Plaintiff’s expert witness. Plaintiff asserted that he was not attempting to withhold Williams’ report from Defendants for several months. Rather, Plaintiff’s counsel was trying to get up to date after their lead counsel had to withdraw from this case for medical reasons, and counsel was not in receipt of Williams’ report when the deadline expired.

    Held

    The Court denied both the Board of County Commissioners for Oklahoma County’s and the Oklahoma County Criminal Justice Authority’s motions to strike the testimony of Plaintiff’s expert witness, Phil Williams.

    Key Takeaway

    The determination of whether a Rule 26(a) violation is justified or harmless is entrusted to the broad discretion of the district court because the decision to exclude evidence is a drastic sanction.

    Case Details:

    Case Caption: Altstatt V. Board Of County Commissioners For Oklahoma County
    Docket Number: 5:22cv811
    Court Name: United States District Court, Oklahoma Western
    Order Date: January 28, 2026
  • Law Enforcement Expert Was Allowed to Opine on Chemical Munitions

    Law Enforcement Expert Was Allowed to Opine on Chemical Munitions

    Wesley Cotton alleged that on March 19, 2022, an incident occurred on Yard 3C at California State Prison, Corcoran (“CSP-Corcoran”), in which officers deployed multiple chemical agents, including oleoresin capsicum (“OC”), chloroacetophenone (“CN”), chlorobenzalmalononitrile (“CS”) grenades (collectively, “chemical agents”) to stop a fight between third party prisoners.

    At the time the chemical agents were deployed, Cotton was located on an adjacent yard, 3B. Cotton alleged that Defendant Medina failed to protect him from exposure to the chemical agents which travelled from Yard 3C into Yard 3B, where he was locked in a caged enclosure. The alleged exposure caused Cotton to choke and injured his eyes, lungs, and body.

    Cotton challenged the testimony of Defendant’s expert witness, Sgt. M. Contreras, an armory sergeant at CSP-Corcoran, on multiple grounds.

    Law Enforcement Expert Witness

    M. Contreras is a veteran law enforcement officer with nearly twenty-five years of experience and has worked as an armory sergeant at CSP-Corcoran since 2017 where he became familiar with the facilities and layout of Yards 3B and 3C. 

    Over the course of his career, Contreras developed extensive and specialized knowledge regarding the maintenance, handling, and use of chemical agents and use-of-force munitions including OC, CN, and CS gas grenades.

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

    Discussion by the Court

    a. Objection to Defendant’s Rule 26 Disclosures 

    Cotton moved to exclude the testimony of M. Contreras under FRCP 26(a)(2) and 37(c)(1), alleging that Defendant is trying to “sneak in” M. Contreras as a new witness outside of the discovery timeline and without proper notice.

    To begin with, Cotton claimed that Defendant failed to disclose Contreras in the initial or final witness lists (May 11, 2023), the non-expert deadline (January 19, 2024), or the expert deadline (February 23, 2024) and that Defendant failed to show substantial justification or lack of harmlessness for the late disclosure or harmlessness.

    The Court noted multiple deficiencies in Cotton’s argument, mainly that according to the “Second Scheduling Order” in this case, the deadline for all parties to serve their expert disclosures was August 15, 2025.

    Defendant provided evidence that she did in fact timely disclose and serve on Cotton the Rule 26 expert report for M. Contreras on August 15, 2025, more than 90 days before the January 27, 2026 scheduled trial date.

    b. Motion to Strike

    i. Daubert Admissibility

    Contreras relied on “his experience and training on the nature, use, and effective range of the specific chemical munitions deployed in the underlying incident” in formulating his opinion that an individual located on CSP-Corcoran’s 3B Yard – located approximately 750 feet south of where chemical agents were deployed on CSP-Corcoran’s 3C Yard during the March 19, 2022 incident and separated by multiple buildings – would not have been affected by the chemical agents. Furthermore, in reaching his opinion, Contreras reviewed reports from the March 19, 2022 incident, surveillance-camera and body-worn camera footage of the incident and conducted a physical inspection and measured the incident location.

    In a motion related to Contreras’ testimony, Cotton claimed that “as only an armory officer/sergeant, Contreras presents no accredited training in CN chemical composition, gas dispersion or meteorology – yet seeks to offer scientific-type opinions.” However, Cotton does not elaborate on Contreras’ alleged lack of qualifications, lack of personal knowledge, or his accusation that allowing M. Contreras to testify would constitute “unfair prejudice/confusion/waste given CCPOA allegiance and armory-only role.”

    As a result, the Court is satisfied that Contreras’ “specialized knowledge and experience can serve as the requisite ‘facts or data’ on which [he may] render an opinion.” Contreras has provided the “how and why” underlying his conclusions and opinion in this case, which appears to be, at least in part, his knowledge and expertise with the CSP Corcoran premises and the nature, use, and effective range of the specific chemical munitions at issue in this caser to arrive at his conclusion. The Court also found that there is no evidence of Contreras showing improper “allegiance” to either Defendant or CSP-Corcoran.

    ii. Exclusion under Rules of Evidence 602, 802, 701(c), and 403

    Cotton complained that Contreras’ testimony and expert report failed to satisfy the criteria of the various Federal Rules of Evidence.

    As a threshold matter, because Defendant intended to have Contreras testify as an expert witness, Cotton’s invocation of Federal Rules of Evidence 602 and 701(c) as grounds for exclusion are unavailing.

    Cotton’s invocation of Rule 802 and 403 was similarly unpersuasive. Out-of-court statements are inadmissible hearsay when they are offered to prove the truth of the matter asserted.

    Cotton did not explain how Contreras’ testimony or expert report constitutes inadmissible hearsay, as Contreras’ opinion appeared to be based on non-hearsay evidence, including his professional training, operational experience, physical inspection and measurement of the incident locations, and review of surveillance and body-warn-camera footage of the incident.

    Held

    The Court denied Cotton’s motions to strike the testimony of Defendant’s expert witness, M. Contreras.

    Key Takeaway

    An expert need not rule out every potential cause in order to satisfy Daubert, as long as the expert’s testimony addresses obvious alternative causes and provides a reasonable explanation for dismissing specific alternate factors identified by the defendant.

    Case Details:

    Case Caption: Cotton V. Medina
    Docket Number: United States District Court for the Eastern District of California
    Court Name: 1:22cv568
    Order Date: January 19, 2026
  • Law Enforcement Expert’s Testimony on the Use of Pepper Spray Limited

    Law Enforcement Expert’s Testimony on the Use of Pepper Spray Limited

    Plaintiff LaBlanca Sibley’s excessive force claim against Officer Nicholas S. Riggall, arising from her arrest and detention, was based on Riggall’s use of pepper spray while she was seated in the patrol car.

    Sibley retained Mr. Jeronimo Rodriguez, an expert in law enforcement practices and use-of-force standards. Riggall moved to exclude Rodriguez’s opinions and testimony. Riggall challenged Rodriguez’s qualifications, methodology, and helpfulness to the trier of fact.

    Law Enforcement Expert Witness

    Jeronimo “Jerry” Rodriguez served as a police officer with the Los Angeles Police Department for over 25 years, including work in the Force Investigation Division.

    Since retiring as an active law enforcement officer in 2021, Rodriguez has reviewed and consulted on police and law enforcement practices as a private police consultant and audited agencies across the country and continued to train many agencies throughout the United States on police-related investigations.

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

    Discussion by the Court

    Qualifications

    Riggall pointed out that Rodriguez has not “studied, personally conducted research, or authored any literature on the use of force at issue in this case.”

    First, Riggall’s argument on qualifications, made conclusorily and without citations to any authority, is insufficiently developed for the Court to consider.

    Regardless, Rodriguez is qualified to testify as a police practices expert generally and about the use of force specifically. Rodriguez has served as a law enforcement officer for decades. For some of those years, he conducted investigations into officers’ uses of force. Since his retirement from law enforcement, Rodriguez has worked as a police practices expert in other cases and has consulted and provided trainings on various police practices subjects.

    Reliability

    Riggall argued that Rodriguez’s opinions “are not based on sufficient or accurate data” because, among other things, Rodriguez supposedly “draws his opinion on the force being excessive largely upon his belief that Sibley was falsely arrested and had not been resisting or involved in any crime.”

    The Court found Rodriguez’s methodology sufficiently reliable. Rodriguez described his methodology thusly: his “method for forming opinions relies on nearly forty years of experience as a police officer and trainer, collaboration with various instructors and police practices experts, and a comprehensive review of relevant evidence and materials, without making credibility judgments.”

    To the extent Rodriguez allegedly relied on Sibley’s version of events, such reliance did not merit exclusion of Rodriguez’s opinions.

    Assistance to the Trier of Fact

    Riggall argued that Rodriguez’s opinions will not be helpful to the jury because “Rodriguez never explains, beyond his own characterization of Plaintiff’s behavior as ‘tapping merely to get an officer’s attention to plead her innocence,’ the basis for not permitting a reasonable officer to interpret Plaintiff’s behavior as violent or aggressive.” He also argued that “Rodriguez offered legal opinions in the guise of interpreting the [Lakeland Police Department’s] policy on use of force.”

    However, the Court rejected this argument in part. Rodriguez’s opinions on the use of force and police practices will be helpful to the jury. Likewise, Rodriguez’s opinion on whether Riggall behaved in accordance with police procedures will be helpful to the jury.

    Although most of Rodriguez’s opinions and report do not contain legal conclusions, he did characterize the use of pepper spray as “excessive.” Calling the use of force “excessive” is a legal conclusion, given the jury is tasked with deciding whether the use of force was “excessive” and, therefore, unconstitutional. As a result, the Court will not allow Rodriguez to opine that the use of force was “excessive.” 

    Held

    The Court granted in part and denied in part the Defendant Nicholas S. Riggall’s motion to exclude the testimony of Plaintiff’s expert Jeronimo Rodriguez.

    Key Takeaway

    An expert is permitted to base his opinion on a particular version of disputed facts and the weight to be accorded to that opinion is for the jury.

    Case Details:

    Case Caption: Sibley V. City Of Lakeland
    Docket Number: 8:24cv2853
    Court Name: United States District Court, Florida Middle
    Order Date: January 27, 2026
  • Law Enforcement Expert’s Testimony on Workplace Dynamics Admitted

    Law Enforcement Expert’s Testimony on Workplace Dynamics Admitted

    Solangie Acosta was a Muskegon Heights Police Department(“MHPD”) law enforcement officer between 2017 and 2022 who brought nine claims against her former employer, alleging discrimination on the basis of sex, disability status, and an exercise of her worker’s compensation rights.

    Defendants filed a motion to preclude testimony by Acosta’s expert Wendy Patrick, a former prosecutor and law enforcement trainer, who intended to testify regarding law enforcement practices and the difficulty that officers face in making complaints, including sexual harassment complaints, against other officers and their superiors.

    Law Enforcement Expert Witness

    Wendy L. Patrick, J.D., Ph.D. has been researching, training, presenting, and publishing within the field of gender discrimination and sexual harassment for over 20 years. She regularly teaches and trains on the insidious progression of gender-based discrimination and harassment within professional relationships, why victims remain employed in positions of power inequality when they are targeted, and the hallmarks of a discriminatory workplace culture.

    Patrick is a certified Institute of Criminal Investigation (ICI) Certified Trainer for law enforcement and provides consulting services and training in trauma-informed sexual assault response and investigation on a national level.

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

    Discussion by the Court

    Defendants moved to preclude Patrick’s testimony on “empirical documentation and testimony regarding workplace dynamics including discrimination, sexual harassment, and retaliation within a male-dominated workplace” and “the potential adverse effects likely to impact a female law enforcement officer targeted as described.”

    Defendants argued that Patrick lacked sufficient qualifications and that Patrick’s expert report “at no point even attempts to discuss, reference, or even acknowledge the facts of this case” given that “the only [case-specific] documents reviewed and information considered was Plaintiff’s First Amended Complaint.”

    Acosta responded that Patrick’s expert report and curriculum vitae establish that she has specialized knowledge as a certified law enforcement trainer and as a published author regarding law enforcement practices. Acosta submitted persuasive authority from federal trial courts indicating that such testimony may be admissible in sexual harassment cases involving police officers.

    Defendants, however, have not presented any controlling Sixth Circuit authority indicating that general expert testimony on the subjects noted in Patrick’s report should be excluded on the facts presently before the Court.

    The Court concluded that Defendants have failed to establish the wholesale inadmissibility of Patrick’s expert testimony.

    That said, Defendants are free to object to specific opinions offered by Patrick if they, for example, violate Federal Rule of Evidence 403 or any other applicable rules. Defendants are also free to object if Patrick attempts to apply her general testimony to the specific facts of this case to the extent that Patrick failed to disclose such an opinion in her expert report.

    Held

    The Court denied Defendants’ motion in limine to exclude the testimony by expert Wendy Patrick without prejudice subject to the guidance provided above.

    Key Takeaway

    Expert testimony about the tendencies of victims of sexual harassment does not require specific knowledge about the parties. Experts routinely offer general testimony about their field of expertise without knowledge of the case at bar.

    Case Details:

    Case Caption: Acosta V. Muskegon Heights
    Docket Number: 1:23cv972
    Court Name: United States District Court, Michigan Western
    Order Date: January 06, 2026
  • Law Enforcement Expert’s Testimony on Tunnel Vision Excluded

    Law Enforcement Expert’s Testimony on Tunnel Vision Excluded

    Eric Kelley contended that he was wrongfully incarcerated for a 1993 murder and robbery for 24 years until DNA testing provided a basis for the trial court to vacate his convictions, and the State declined to retry him, Kelley then sued several members of the Paterson Police Department (“PPD”) who allegedly violated his constitutional rights and the City of Paterson (“Paterson”).

    To testify at trial, Paterson retained Ronald Hampton, a twenty-five-year veteran of the New Jersey State Police, as an expert witness on the policies and procedures of the PPD during the relevant time. Plaintiff, however, filed a motion to exclude the testimony of Defendant’s expert, Hampton.

    Law Enforcement Expert Witness

    Ronald Hampton, M.A., CFE served for twenty-five (25) years with the New Jersey State Police in various assignments and capacities before retiring on September 1, 2019.

    He graduated from Fairleigh Dickinson University, Rutherford, New Jersey, with a Bachelor’s Degree in Political Science in 1992 and Rutgers University, Newark, New Jersey, with a Master’s Degree in Criminal Justice in 2003. Hampton also attended and graduated from American Military University with a Master’s Degree in Management in 2014. He is a graduate of the 241st session of the FBI National Academy (2010). He is also a Certified Fraud Examiner (CFE), having received certification in 2018.

    Discover more cases with Ronald Hampton as an expert witness by ordering his comprehensive Expert Witness Profile report.

    Discussion by the Court

    The parties dispute Hampton’s social psychology qualifications, the reliability of Hampton’s methodology, and the fit between his proffered testimony and the issues in this case.

    1. Rebuttal Report

    The Court excluded Hampton’s entire proffered rebuttal testimony because his rebuttal report intrudes on the province of the jury by making credibility determinations, opining on legal issues, and regurgitating fact witness testimony.

    First, Hampton inappropriately commented on witnesses’ knowledge or understanding. Second, Hampton improperly opined about legal requirements. Lastly, Hampton unacceptably weighed conflicting evidence and witnesses’ credibility.

    Additionally, Hampton threatened to waste trial time by regurgitating deposition testimony with minimal to no analysis. Basically, Hampton’s summaries of witness testimony “are matters that would be within the common understanding of regular citizens and do not require—and are not benefited by—the opinions of a police practices expert.”

    Finally, Hampton is not a social psychologist, yet he discusses psychological concepts such as tunnel vision, contamination, and psychological factors relating to Kelley’s confession.

    In sum, the Court excluded Hampton’s rebuttal report for invading the jury’s province, and for offering new opinions improperly raised on rebuttal.

    2. Opening Report

    To begin with, Hampton’s opening report generally marched through the background of the PPD’s policies and procedures in effect in 1993, how those policies compared to those in place at other law enforcement agencies, and how they evolved over time.

    Although Plaintiff conceded that such testimony could assist “in determining whether the [police] practices differed from standard law enforcement practices,” the Court nonetheless had to address Plaintiff’s objections to Hampton’s methodology.

    Hampton’s “application of extensive experience to analyze” the PPD’s policies and procedures is a reliable methodology based on his 25 years with the New Jersey State Police.

    Nevertheless, the Court excluded several lines of testimony within the opening report. First, Hampton may not testify about irrelevant matters, such as, inter alia, the rules governing officer appearance. Second, Hampton may not reference the testimony of fact witnesses in this case, as he does with Lieutenant Spagnola and Chief Munsey. Third, Hampton may not speculate. Finally, Hampton may not utilize materials prepared after 1993 to support opinions regarding policies or procedures in place in 1993. 

    Held

    The Court granted in part and denied in part the Plaintiff Eric Kelley’s motion in limine to exclude the testimony Defendants’ expert Ronald Hampton.

    Key Takeaway

    Police experts regularly testify about non-scientific topics based on their own training and experience. Hampton made several assertions about the PPD’s policies and procedures, which he attempted to prove based on his own extensive training and experience.

    Case Details:

    Case Caption: Kelley V. Reyes
    Docket Number: 2:19cv17911
    Court Name: United States District Court, New Jersey
    Order Date: January 14, 2026
  • The Law Enforcement Expert Was Allowed to Opine on Pennsylvania State Police Policy

    The Law Enforcement Expert Was Allowed to Opine on Pennsylvania State Police Policy

    The Defendants are Pennsylvania State Police Troopers accused of using excessive force when they served a 302 warrant on Plaintiff Carl Giuli based on his wife’s reports that Giuli was experiencing a mental health crisis. While serving the warrant, an altercation occurred in Giuli’s house involving Giuli and Pennsylvania State Police Troopers Joseph Montagna and Christopher Teetsel. Giuli sustained injuries in the course of the altercation which he alleges are due to the use of excessive force by Troopers Montagna and Teetsel.

    The Defendants sought to preclude Thomas Shea, the Plaintiff’s proffered use of force expert, on several grounds. In their motion, Defendants stated that Shea’s expert report is not appropriately considered by the jury on several grounds: 1) he was a municipal officer rather than a state police trooper as are Defendants in this case; 2) he uses “amorphous methodologies with no reliability”; 3) he “invades the province of the jury by declaring that excessive force was used and the testimony of the troopers is not credible”; and 4) his opinions about trooper training are not supported.

    Law Enforcement Expert Witness

    Thomas A. Shea III, D.Sc., CPP is a nationally recognized Law Enforcement and Security expert in policing best practices, security standards, and emergency preparedness, specializing in police operations, use of force, premises liability, negligent security, and related civil litigation issues.

    He started his career with the Long Branch Police Department in 1998 after serving honorably in the United States Marine Corps during Operation Desert Storm. During his career, Shea served as an agency police commander and on the Monmouth County Emergency Response Team (SWAT).

    After completing his police career in February 2017, Shea entered academia. Shea recently served as the director and founder of the Law Enforcement Executive Leadership program at Seton Hall University.

    He has published numerous academic and professional articles and a police practice book, created a law enforcement and security leadership higher education curriculum, and presented nationwide at professional conferences on security and policing topics.

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

    Discussion by the Court

    A. Reliability

    The Defendants first asserted that Shea’s report consisted of inaccuracies and factual errors that cast serious doubt on the reliability of his opinion.

    The Defendants maintained that Shea’s reliability is doubtful because Shea did not use the New Jersey Law Enforcement Handbook in making his determinations despite his report saying that he did. Critically, Shea’s report stated that it was Defendant Montagna who pushed Plaintiff Giuli up against the refrigerator in the course of this incident; there is no allegation of this in the record, and Shea offered inconsistent explanations for why this factual averment appears in his report.

    The Court found that the inconsistencies found in his report and other matters that relate to the reliability of his opinions are properly the subject of cross-examination to the extent he is allowed to testify on those matters at trial.

    B. Credibility Determinations

    The Defendants next argued that Shea’s opinions regarding credibility are inappropriate. The jury has the exclusive function of appraising credibility, determining the weight to be given to the testimony, drawing inferences from the facts established, resolving conflicts in evidence, and reaching ultimate conclusions of fact.

    The Court agreed with the Defendants that “the case presented to the Court is one of credibility—ultimately the jury will have to determine if Defendants maliciously assaulted Plaintiff or if they used appropriate force after he attacked them.” Regarding the different versions of events offered by the Plaintiff and Defendants, Shea confirmed at the Daubert Hearing that the parties’ “stories differ in some aspects” and that he “intended to offer an opinion to the jury as to who they should believe or find credible.”

    Shea also acknowledged that he made other credibility determinations in the course of his report, including those related to the cause of Plaintiff’s injuries, and he believed that was “a typical purview of a use of force expert.” As a result, Shea was precluded from offering any opinions on credibility at trial. 

    C. Specific Opinions

    1. Compliance with Non-Relevant Standards

    Defendants asserted that the Plaintiff sought to admit Shea’s opinion regarding Defendants’ compliance with non-relevant standards. The Court found that Plaintiff has not shown that “prevailing national standards in the use of force” are relevant in this case or that the specifically identified President’s Task Force on 21st Century Policing Final Report and Law Enforcement Best Practices: Lessons from the Field are relevant.

    Therefore, Shea was precluded from relying on these publications and testifying about standards promulgated therein, i.e., the goal of “avoiding the use of force if at all possible, even when it is allowed by law and policy” identified in The President’s Task Force on 21st Century Policing and the “principles of de-escalation” identified in Law Enforcement Best Practices.

    Similarly, the Court precluded Shea from testifying about Plaintiff’s generically identified intent to elicit an opinion on “prevailing national standards in the field of use of force.”

    2. Pennsylvania Mental Health Procedures Act

    Plaintiff has not shown the relevance of the Pennsylvania Mental Health Procedures Act to the charge against the Pennsylvania State Troopers executing the warrant and has not shown how testimony about provisions in the Act would assist the trier of fact as required under Daubert.

    The Court held that Shea’s testimony about the Act at the Daubert Hearing made no direct connection between the Act and the facts of this case, opining generally that “what he took” from the Act is that “you have to take extra, extra precautions to communicate more thoroughly. You have to be more patient than you normally would during a call because lots of people going through these crisis events aren’t aware . . . of their actions and decisions.”

    This is not a State Police policy, it is not presented as a policy statement found in the Act or one that is applicable to officers issuing a 302 warrant. Therefore, the Court found that reference to the Act is properly precluded based on relevance and fit grounds.

    3. Compliance with Pennsylvania State Police Policy

    Defendants next took issue with Plaintiff’s proposed opinion as to whether Defendants were compliant with Pennsylvania State Police policy.

    Defendants specifically asserted that Shea “should be prevented from testifying as to whether or not Defendants complied with the PSP policy, as he has not established his opinion is any more reliable than a lay witness simply reading the Pennsylvania State Police policies and opining on whether or not they were followed in this case.”

    The Court found that Shea has a breadth of knowledge and experience in police practices and use of force which render him qualified to testify as an expert as limited herein. Further, Pennsylvania State Police policies are relevant for purposes of this case and an expert’s review of pertinent policies will assist the trier of fact.

    4. Compliance with De-escalation Policy

    Defendants relatedly contended that it did not appear that Shea based his opinion regarding de-escalation on Pennsylvania State Police policy; “rather he based his opinion on ‘Law Enforcement Best Practices: Lessons from the Field . . . [and] only on Plaintiff’s version of events as he made a credibility determination regarding the Defendants’ narrative.”

    It should be noted that an opinion based on Law Enforcement Best Practices is precluded and an opinion based on a credibility determination is also precluded. 

    5. Use of Excessive Force Language

    Finally, Defendants objected to the Plaintiff’s intention to elicit Shea’s opinion on whether the force used was “reasonable and necessary, with no mention of the word, excessive, no mention of the case law, no mention of factors.”

    The Court concluded that Shea is appropriately precluded from use of the words “reasonable” or “unreasonable” in rendering his opinion regarding excessive force. Testimony by Shea regarding reasonableness “would usurp the District Courts’ pivotal role in explaining the law to the jury.”

    Held

    The Court granted in part and denied in part the Defendants’ motion to exclude the testimony of the Plaintiff’s use of force expert, Thomas Shea.

    Key Takeaway

    The Court acknowledged that Shea’s report is problematic for multiple reasons, including those cited. However, focusing on Shea’s knowledge and experience summarized at the Daubert Hearing and set out in his Curriculum Vitae, the Court found that Shea has a breadth of knowledge and experience in police practices and use of force which render him qualified to testify as an expert.

    Case Details:

    Case Caption: Giuli V. Montagna
    Docket Number: 3:23cv1785
    Court Name: United States District Court for the Middle District of Pennsylvania
    Order Date: January 08, 2026
  • Law Enforcement Expert Was Not Allowed to Opine on the Party’s Intent

    Law Enforcement Expert Was Not Allowed to Opine on the Party’s Intent

    Plaintiff Deborah Jones-MacDonald brought this civil rights action against Defendants, Harris County Sheriff’s Office (“HCSO”) Deputies Ronaldo Delgado and Charles Ribbe (collectively, “the Deputies”), alleging that she suffered personal injuries as a result of an August 13, 2021 encounter with the Deputies.

    Plaintiff sought to exclude the report of the Deputies’ expert, Michael A. Dirden, as “methodologically unsound, legally improper, and factually unreliable.”

    Law Enforcement Expert Witness

    Michael Antony Dirden began his public service career in 1985 as an officer with the Houston, Texas Police Department (HPD) and served there for three decades in progressive ranks including Executive Assistant Chief of Police and Attorney. During his tenure Dirden was instrumental in establishing collaborative accountability protocols for force and internal investigations with the City of Houston Citizen’s Review Committee and the HPD while leading the Internal Investigations Command and serving as Inspector General for the City of Houston. Dirden also led the Professional Standards and Criminal Investigations Command.

    Dirden has worked with the United States Department of Justice, the United States Office of Community Oriented Policing, and the California Department of Justice as a subject matter expert addressing internal affairs and accountability, use of force and officer-involved shootings, and leadership.

    He earned a Doctor of Jurisprudence from the South Texas College of Law, a Master’s Degree in Criminal Justice from the Sam Houston State University, and a Bachelor’s Degree in Economics from the University of Texas – Austin.

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

    Discussion by the Court

    Dirden opined that “Delgado’s action could be determined to be reasonable.” Whether Delgado was ‘acting reasonably’ is, for all practical purposes, the only issue for the jury in this case to decide. Therefore, the Court held that Dirden’s opinion on this point is inadmissible. 

    Similarly, Dirden’s opinion that “another reasonable and prudent officer could have acted in the same manner under the same or similar circumstances” is just another way of saying that Dirden believes the Deputies’ actions were reasonable. That is, however, another question for the jury to answer.

    Dirden opined “the fact that the use of force result in injury, as alleged in this lawsuit, does not mean that the force was unreasonable or excessive. Nor does the age or race of the subject play a role in determining the reasonableness of the force.” Dirden continued: “Even if it is subsequently determined that the Defendants’ reason for attempting to detain the Plaintiff was in error, it still does not give the Plaintiff the right to resist the detention by assaulting Deputy Delgado.”

    These are not merely Dirden’s opinions. These are instructions on the law. Such instructions may come only from the trial court. The Court held that Dirden will not be allowed to instruct the jury on the law through his “expert opinion.”

    Some of Dirden’s opinions are unhelpful and speculative. For example, Dirden opined that “Plaintiff was not willing to comply with the Defendants and in fact, escalated the situation.” This is not a subject that requires expert testimony. It is for the jury—and only the jury—to assess the Plaintiff’s and the Deputies’ actions and, to the extent it is necessary, determine any of the parties’ intentions. Experts “may not speculate about a party’s intent.”

    Held

    The Court granted Plaintiff’s motion to exclude the testimony of Defendants’ expert, Michael Dirden.

    Key Takeaway

    Experts cannot render conclusions of law or provide opinions on legal issues. It is therefore error to allow expert testimony on whether an officer used unreasonable force. There can be only one spokesman of the law, who of course is the judge.

    Case Details:

    Case Caption: Jones-Macdonald V. Harris County
    Docket Number: 4:23cv2871
    Court Name: United States District Court, Texas Southern
    Order Date: December 09, 2025