When a Cop Becomes an “Expert”: What U.S. v. Binzel Teaches Us About Lay Opinion Under FRE 701

By Arjan Bir Sodhi for LexRepublica.com

In everyday trials, we tend to assume that a police officer who testifies is simply telling the jury what they saw: who ran, who spoke, who carried what. But modern evidentiary law draws a hard line between what a witness actually observed and what that witness thinks those observations mean. That distinction becomes especially important when the “meaning” depends on training, tactics, and experience — in other words, when a simple observation becomes expert analysis in disguise.

This tension sits at the heart of United States v. Binzel, a quiet but influential federal case that essentially asks one question:

When does an officer stop being a witness and start becoming an expert?

The answer comes from the often-misunderstood Federal Rule of Evidence 701, the rule that governs lay opinions. And Binzel shows how quickly courts will shut down testimony when law enforcement crosses the line.

The Case: What Happened in U.S. v. Binzel?

The prosecution in Binzel relied on officers who watched the defendant’s behavior and offered opinions about it. These weren’t just simple descriptions — they were interpretations. Officers testified, for example, that the way a package was exchanged, or the manner in which certain movements occurred, was “consistent with drug trafficking.”

The defense pushed back, arguing that these weren’t lay observations at all. This was expert testimony dressed in street clothes — and if officers wanted to offer those interpretations, they needed to qualify as experts under Rule 702, with the disclosures, credentials, and reliability checks that come with it.

The appellate court agreed. It held that the officers’ testimony slipped into areas that relied on specialized knowledge about drug operations and investigative patterns — exactly the type of expertise that Rule 701 forbids for a lay witness.