Law Enforcement Expert Permitted to Testify on the General Reasonableness of Police Conduct
Posted on June 17, 2025 by Expert Witness Profiler
This lawsuit arises out of an incident that took place on November 11, 2019, in which Phoenix Police Department Officer Brittany Smith-Petersen shot and injured Plaintiff Krish Singh during a law-enforcement encounter.
Defendants brought a partial Daubert motion seeking to preclude certain portions of the intended testimony of Plaintiff’s use-of-force expert, Roger Clark.
Law Enforcement Expert Witness
Roger Clark is a retired law enforcement professional with 27 years of experience in the Los Angeles County Sheriff’s Department (LASD). He was hired on December 1, 1965, and served until his retirement on March 31, 1993. Throughout his distinguished career, he held several key positions, including six years as a Deputy Sheriff, six years as a Sergeant, and 15 years as a Lieutenant. Roger retired with a California Peace Officer Standards and Training (POST) Advanced Certificate and is a graduate of the POST Command College, class #5, 1988.
Discussion by the Court
Ultimate-Issue Testimony
To begin with, Clark’s assertion that the Officers’ conduct was “in violation of . . . law as taught to all officers” does more than simply provide an aid to the jury’s deliberation. It is, on its face, a legal opinion. Although the statement is technically qualified by the phrase “as taught to all officers,” the Court finds such qualification insufficient and more likely to confuse than to illuminate.
The rest of Clark’s report is more complex to evaluate. Many of the statements challenged by the Defendants use terms like “excessive” or “unreasonable.” These terms are tricky because they carry both everyday meanings and specific legal implications. It is appropriate for an expert like Clark to give opinions on what a reasonable police officer might do in a certain situation, based on standard training and professional norms. Using terms like “unreasonable” or “excessive” in that context does not automatically violate the Federal Rules of Evidence.
However, Clark is not allowed to directly state that Officers Smith-Petersen or Batway acted unreasonably. Such a statement crosses the line from expert opinion into a legal conclusion, which is not permitted. Clark’s report walks a fine line—sometimes staying within proper boundaries, and other times crossing them.
Most of the statements flagged by Defendants as improper could be corrected by rewording. Rather than examine every sentence now, the Court establishes a general rule and will address specific issues during the trial. Clark may testify about what constitutes reasonable or excessive force in general terms, but he may not say whether the specific officers in this case acted unreasonably or used excessive force.
Mental Health Diagnoses
Defendants argued that Clark’s report improperly offered an opinion about whether the Plaintiff was suffering from a mental disorder at the time of the incident. The Court disagrees, finding that this misrepresents the report. In the report, Clark explicitly states that it is not the role or ability of police officers to diagnose a person’s disability. However, he also explains that officers are trained to recognize signs and cues that help them make appropriate decisions about how to respond. This training often involves mental health frameworks that guide officers in identifying possible mental health issues during their interactions with the public.
Based on this training, Clark opined that the Officers should have recognized that the Plaintiff might be mentally ill or emotionally distressed—especially when the Plaintiff repeatedly asked them to kill him, a clear indication of mental distress. Clark’s testimony is not a clinical diagnosis. Instead, it is an expert opinion about how a trained officer should interpret observable behavior in the field. The Court found this type of opinion to fall well within Clark’s area of expertise.
Defendants also took issue with a line in the report stating that the Plaintiff “suffered from PTSD, drug addiction, and ADHD.” But they failed to include the full context: that statement appears in the background section of the report and is explicitly attributed to the Plaintiff’s mother, Sunita Singh. Whether that statement qualifies as hearsay is not being decided here. What matters is that Clark himself did not diagnose the Plaintiff with any mental condition.
Contravention of the Video Evidence
Defendants’ final argument under Daubert is that Clark’s report relies on insufficient data because it allegedly contradicts the video footage of the incident. They claim Clark misrepresented the facts by stating that the Plaintiff did not advance toward the officers, asserting instead that “the video clearly shows Singh advancing toward the officers multiple times.”
Defendants also argue that Clark’s report is flawed because he claimed the officers failed to use de-escalation techniques. In contrast, Defendants insist they did employ such techniques, including issuing over twenty commands for the Plaintiff to drop his weapon or stop moving, speaking with him, and reassuring him that they did not believe he was mentally unstable.
However, the Court found that most of Defendants’ arguments simply quoted portions of Clark’s report without explaining how those statements actually contradict the video evidence. Even in the few instances where Defendants attempted to point out specific inconsistencies, the Court found their arguments unconvincing.
Held
The Court granted in part and denied in part the Defendants’ partial Daubert motion to preclude certain portions of the intended testimony of Roger Clark.
Key Takeaway:
The Court ruled that while Clark may testify about general police practices and how a reasonable officer should interpret signs of mental distress, he may not offer legal conclusions—such as stating that the officers acted unlawfully or unreasonably. His mental health observations were deemed within his expertise and not clinical diagnoses. The Court also rejected Defendants’ argument that Clark’s report contradicted video evidence, finding their objections vague and unpersuasive.
Case Details:
| Case Caption: | Krish Singh V. City of Phoenix |
| Docket Number: | 2:21cv99 |
| Court Name: | United States District Court, Arizona |
| Order Date: | June 12, 2025 |
