Appellant was convicted of robbery and false imprisonment. On appeal, he challenged the admission of testimony as to his and a defense witness’s gang affiliation, as well as testimony by a detective who claimed to be a gang expert about certain characteristics of gangs. The appellate court here reversed. Although the testimony about appellant’s gang affiliation was admissible as impeachment evidence, the expert testimony was not. The testimony had no relevance as impeachment, and the prejudicial value of the testimony was significant. Further, the limiting instruction regarding the gang evidence did not assure that its prejudice would be defused.