Colorado’s second-highest court on Thursday overturned a man’s drug convictions and 36-year prison sentence because a law enforcement officer improperly testified the defendant had met the legal elements to be found guilty.

An expert witness cannot “usurp” the jury’s role by testifying about the conclusion jurors should reach. The Court of Appeals has previously ordered new trials in cases where experts suggested, for example, that it was unlikely victims would falsely report being sexually assaulted or that victims’ allegations of abuse were credible.

After a 2023 trial, jurors found Jose Meza-Franco guilty of three charges of conspiring to sell drugs and a fourth charge of money laundering, based on the drug conspiracy. Law enforcement never observed Meza-Franco with narcotics, did not have physical evidence, and a search of his home only turned up a large quantity of cash — in a bedroom that was not his.

Instead, the evidence of Meza-Franco’s alleged participation in a drug-dealing conspiracy largely came from a series of wiretaps on the phone of another man, who law enforcement identified as a leader of the conspiracy. At some point, police believed Meza-Franco was a source of narcotics for the leader.

Investigator Valentin Oliveros, who was the lead investigator on the case, also testified as an expert in narcotics, distribution and “terminology.” To that end, large parts of his testimony involved interpreting the phone calls for jurors, in which Meza-Franco both spoke in Spanish and used apparently coded language to refer to drug deals.

Although the defense objected at the outset to Oliveros interpreting the phone calls for the jury, District Court Judge Vincente G. Vigil ruled Oliveros could testify “as to what he believes” the recorded conversations were about.

Eventually, the prosecutor began asking Oliveros to opine about whether Meza-Franco’s conduct satisfied the legal elements of the offenses, including:

• whether the cocaine “that was conspired to either be distributed or possessed with the intent to be distributed” was within the correct range

• whether Meza-Franco “engaged in a financial transaction”

• whether Meza-Franco “completed that financial transaction with the intent to promote” the distribution of cocaine

On appeal, Meza-Franco argued Oliveros’ testimony was problematic for multiple reasons, and a three-judge Court of Appeals panel agreed with him in part.

Judge Pax L. Moultrie, writing in the April 3 opinion, explained Oliveros improperly gave his opinion about whether the defendant’s conduct satisfied the elements of the crime, which was a decision for the jury alone to make.

“Indeed, in response to the prosecutor’s questions that used legal language, Investigator Oliveros directly opined that Meza-Franco’s actions,” she wrote, “satisfied the elements of money laundering. In doing so, Investigator Oliveros effectively testified that Meza-Franco had met each element of the conspiracy charges, all but agreeing with the prosecutor that the legal standards for conspiracy to distribute cocaine had been met and telling the jury that Meza-Franco was guilty.”

Moultrie elaborated the mistake could have affected the outcome, as Oliveros’ interpretation of the wiretapped calls was the centerpiece of the prosecution’s case, without which the alleged criminal behavior would have been less clear.

“We recognize the risk that the jury possibly afforded Investigator Oliveros’s improper testimony ‘particular weight and credibility’ because he testified as an expert, was employed by the government, and testified to complex matters,” she wrote.

The panel ordered a new trial.

The case is People v. Meza-Franco.