Appellant appeals the final order adjudicating him to be a delinquent juvenile. The sole issue he raises on this appeal is the failure of the trial judge to conduct a hearing pursuant to Richardson v. State, 246 So.2d 771 (Fla. 1971), before excluding the testimony of appellant’s mother for not having been listed as a witness in pretrial discovery. It is undisputed that there was a failure to conduct such a hearing. We have searched the record to determine whether the trial judge conducted the equivalent of such a hearing but find no evidence that such was the case. We are prohibited from considering whether the failure to conduct the Richardson hearing was harmless error. We, therefore, must reverse and remand for a new trial.