When a police officer testifies, would you consider them an expert on drugs, guns, and gangs? Many people typically associate their expertise as being limited to law enforcement practices. However, the Iowa Rules of Evidence allow police officers to be designated as “expert witnesses” provided that their opinion on the issue is within their specialized knowledge or expertise.[i] This is problematic because allowing such expert testimony from officers is highly prejudicial to defendants and often lacks sufficient qualification. Therefore, an officer’s expert testimony should be limited strictly to law enforcement protocols. 

To fully understand the issue, it is important to examine how a court’s liberal stance on admitting evidence has shaped our precedent.[ii] Among other things, these rules allow a witness who is qualified as an expert by experience or education to testify in the form of an opinion.[iii] For instance, a witness who has been around a “great deal” of marijuana, smoked it thousands of times, and identified it over 100 times without mistake, has been deemed to have obtained “substantial” experience to qualify as an expert on marijuana in a drug prosecution case.[iv] This demonstrates the expansive view courts take in admitting expert testimony, even when formal education is lacking.

This liberal stance extends to law enforcement testimony in criminal prosecutions.[v] For example, an officer was allowed to testify that, in most cases, a driver found with large quantities of drugs likely transported them knowingly as part of a job.[vi] An officer is qualified to testify as an expert as long as they have experience on the subject matter, their testimony is deemed to provide information beyond the knowledge of laypersons and to aid the jury in determining facts.[vii] It’s troubling that such testimony was admitted based on experience alone as if he had been a one-man DEA agency for drug cases in the last several decades.[viii] Additionally, the Supreme Court did not inquire into whether the officers should back up such statements with statistics.[ix] Notably, the officer’s bias or motive to secure a conviction does not disqualify them from testifying as an expert. Jurors even assume officers do not have a stake in the outcome without realizing officers work closely with the prosecution to seek a conviction.[x] This trend of admitting prejudicial evidence under the guise of expertise restricts the criminally accused’s right to a fair trial.[xi]

The Iowa Rules of Evidence closely mirror the Federal Rules of Evidence and similarly adopt an expansive view of who can qualify as an expert witness.[xii] For example, in State v. Hayes, the defendant was convicted of criminal gang participation.[xiii] To prove the defendant engaged in gang activity, the state offered the expert testimony of a Scott County sheriff.[xiv] The sheriff testified about the principal criminal activities of the Black Gangster Disciples, gang mannerisms displayed by the defendant in photographs, and gang signs drawn in a letter from the defendant to his girlfriend.[xv] The court held the testimony admissible, reasoning that it provided evidence showing one of the gang’s primary activities involved the commission of criminal acts.[xvi] However, the court failed to discuss what made the officer qualified to discuss gang activities. In most cases involving police expert testimony on gangs, all the officer needs are some-gang related training and field experience.[xvii] Allowing such evidence unfairly prejudices the defendant by forcing them to counter police testimony characterizing their actions as gang participation, as jurors are more likely to convict when they believe the defendant was part of a gang.[xviii]

Law enforcement expert testimony should be excluded as prejudicial because it goes against the spirit of the public records exception. The public records exception allows otherwise inadmissible hearsay to come in as evidence in court because public officials have a legal duty to tell the truth, therefore the testimony is inherently reliable.[xix] For example, in State of Iowa v. Wiggins, the defendant was convicted of possessing marijuana with intent to deliver.[xx] To prove the defendant’s intent, the state relied on the expert testimony of a Davenport police lieutenant.[xxi] The officer testified that the marijuana’s weight qualified it for a drug stamp and that its packaging—separated into smaller quantities—indicated intent for distribution rather than personal use.[xxii] The court admitted the testimony, reasoning that the officer did not explicitly state that the defendant had the intent to deliver but merely opined that the packaging was consistent with drug distribution practices.[xxiii]

This testimony unfairly prejudices the defendant because the jury is likely to infer intent to deliver based on the officer’s opinion.[xxiv] While it is established that an expert’s opinion is not objectionable solely because it embraces an ultimate issue, such testimony undermines the rationale of the public records exception. Police reports are excluded under this exception due to their inherent unreliability stemming from officers’ vested interest in securing prosecutions.[xxv] By presenting such opinions as expert testimony, the prosecution circumvents the public records exception, creating a “back door” to admit unreliable and biased evidence.[xxvi] This practice goes against the spirit of the public records exception and compromises the fairness of the trial.

As Iowa’s liberal approach to evidence admission continues to disadvantage criminal defendants —it needs to consider taking a strong stance in raising the bar of who is qualified to give expert testimony. Maybe let’s start with making it clear that an officer who gives expert testimony about the effect of trauma on a person’s “recollection of events” does affect a defendant's substantive rights.[xxvii] After all, a defendant’s case should be decided on substantive tangible evidence, not the biased opinion of officers who benefit from a conviction.[xxviii] For all the reasons stated above, Police expert testimony should not extend to drugs, guns, and gangs.