Colorado’s second-highest court reversed a juvenile defendant’s conviction for unlawful sexual contact on Thursday after an expert witness’s testimony improperly suggested the child victim was telling the truth.

The defendant, identified as S.H-S., was around 16 years old when he allegedly inappropriately touched Y.M., who was 10 years younger than him. Y.M. disclosed the touching to her mother years later and underwent a forensic interview.

During S.H-S.’s trial, an expert in forensic interviewing testified that children are more likely to be honest during interviews if they promise to tell the truth beforehand, according to research studies. Jurors saw Y.M. make such a promise in her forensic interview.

The jury adjudicated S.H-S. delinquent, which is the juvenile equivalent of a guilty verdict.

On appeal, S.H-S. argued that Denver Juvenile Court Judge Laurie Clark wrongly permitted the expert’s testimony in violation of the longstanding prohibition on witnesses testifying about other witnesses’ truthfulness on specific occasions.

A three-judge Court of Appeals panel agreed.

“The jury viewed a recording of Y.M.’s interview, in which Y.M. promised to be truthful. Viewing the interviewing expert’s testimony alongside this evidence, we conclude the expert’s testimony that “(t)he research does state when eliciting a promise from a child, it increases their truthfulness of their statements,’ implied that Y.M. was truthful when she made her allegations,” wrote Judge Daniel M. Taubman in the Sept. 3 opinion.

The panel ordered a new trial.

The case is People in the Interest of S.H-S.