The first issue raised by this appeal is whether the trial court erred in admitting on rebuttal for the purpose of impeachment inculpatory statements made by defendant to the investigating officer during custodial interrogation but denied by defendant at trial.
For the first time since Miranda [Miranda v. Arizona, 384 U.S. 436, 86 S.Ct. 1602, 16 L.Ed. 2d 694 (1966)] laid down definitive rules to prevent police abuse in custodial interrogations, the United States Supreme Court, in Harris v. New York, 401 U.S. 222, 91 S.Ct. 643, 28 L.Ed. 2d 1 (1971), contracted rather than expanded the exclusionary rule by its holding that in-custody statements made voluntarily and understandingly, even though excluded by Miranda from the prosecution’s case in chief as *45substantive evidence, may be used to impeach a testifying defendant’s credibility.
The court rejected the idea that this expansion would encourage impermissible police conduct for that “sufficient deterrence flows when the evidence in question is made unavailable to the prosecution in its case in chief.” However, to be admissible as impeachment evidence, it is clear that the confession must satisfy the legal standards of trustworthiness — that it was voluntarily and understandingly made though Miranda-barred. And see Oregon v. Hass, 420 U.S. 714, 95 S.Ct. 1215, 43 L.Ed. 2d 570 (1975).
In State v. Bryant, 280 N.C. 551, 187 S.E. 2d 111 (1972), where the State in its case in chief did not attempt to offer the defendant’s custodial confession, but after defendant on cross-examination denied he told law officers that he used a knife and choked the rape victim, the State offered in rebuttal the testimony of an interrogating officer that defendant told him he used a switchblade knife and choked her. Defendant’s admission was Miranda-barred because he admittedly had not waived his right to counsel. The trial court instructed the jury that the evidence was admitted for purpose of impeachment only, but made no finding that the admission was voluntarily and understandingly made. In finding no error the Supreme Court overruled State v. Catrett, 276 N.C. 86, 171 S.E. 2d 398 (1970), which held a Miranda-barred confession not admissible for any purpose, because it was based on an interpretation of the Miranda decision, but that interpretation was rejected by the United States Supreme Court in Harris v. New York, supra.
State v. Bryant, supra, did not discuss the absence of any finding by the trial court that defendant’s admission met the legal standards of trustworthiness, but it does not appear that defendant requested a voir dire or offered evidence contradicting volun-tariness. Though Bryant and Oregon v. Hass, supra, are authority for the proposition that where there is no evidence of involuntariness or coercion the trial court is not required to find that the Miranda-barred admission was voluntary, it is the better practice for the trial judge to chart the admissibility of a Miranda-barred admission by finding, either after voir dire during the State’s case in chief or upon defendant’s objection during rebuttal, whether the statement was voluntarily and understandingly made. And if found to have been voluntarily made, the trial *46judge should find that he was so satisfied by the preponderance of the evidence in order to meet the standard of proof required by the prosecution in Lego v. Twomey, 404 U.S. 477, 92 S.Ct. 619, 30 L.Ed. 2d 618 (1972).
In the case before us we do not find State v. Bryant, supra, to support the admissibility of defendant’s Miranda-barred admission made to the interrogating officer. In the case sub judice the trial court found that the illiterate defendant did not have the mental capacity to understand his right to counsel. This showing of illiteracy and finding of mental incapacity to understand his right to counsel casts some doubt not only upon his capacity to understand any of the Miranda rules but also upon the volun-tariness of his admission in light of defendant’s testimony that the interrogating officers shouted at him and beat on the table. Under these circumstances, with the burden on the State to satisfy the trial judge of voluntariness by the preponderance of the evidence, we find that the trial judge erred in admitting defendant’s admission for impeachment in the absence of a finding of voluntariness. See State v. Langley, 25 N.C. App. 298, 212 S.E. 2d 687 (1975), where the circumstances surrounding the custodial interrogation are somewhat similar to those in the case before us, but the trial judge in Langley did not instruct the jury that the rebuttal testimony was admitted for purpose of impeachment only. The trial court in the case sub judice properly instructed the jury that defendant’s statement was not substantive evidence but for impeachment.
Nor do the circumstances in the case before us justify a finding of harmless error. In Milton v. Wainwright, 407 U.S. 371, 92 S.Ct. 2174, 33 L.Ed. 2d 1 (1972), there was a ruling of harmless error, but there was “overwhelming evidence of guilt,” including three properly admitted pre-indictment confessions that revealed essentially the same information as his statement to the undercover officer. In the case sub judice there were no other properly admitted confessions and the evidence of defendant’s guilt cannot be classed as overwhelming. We find prejudicial error requiring remand to the trial court for determination of whether the statement made by the defendant during custodial interrogation was voluntarily and understandingly made. However, we do not find it necessary to order a new trial because the question of volun-tariness may be determined by the trial court and there was no *47other harmful error. Where there is prejudicial error in the trial court involving an issue or matter not fully passed on and determined by the court, this Court has remanded the action to the trial court for appropriate proceedings to determine the issue or matter without ordering a new trial. See State v. Roberts, 18 N.C. App. 388, 197 S.E. 2d 54 (1973), remanded for determination of whether defendant was denied a speedy trial; State v. Martin, 18 N.C. App. 398, 197 S.E. 2d 58 (1973), remanded for determination of whether there was a plea bargain; State v. Moses, 25 N.C. App. 41, 212 S.E. 2d 226 (1975), and State v. Ingram, 20 N.C. App. 35, 200 S.E. 2d 417 (1973), remanded in both cases for determination of whether identification at trial was of independent origin and untainted by illegal pretrial identification procedure.
We have carefully examined the defendant’s three other assignments of error and find that they involve matters which rest largely within the broad discretion of the trial judge, and we find no abuse of discretion and no showing of harmful prejudice.
Therefore, this cause is remanded to the Superior Court of Wake County where a judge presiding over a criminal session will conduct a hearing, after due notice and with defendant and his counsel present, to determine whether the statement allegedly made by the defendant to Deputy Sheriff R. D. Lockamy, a rebuttal witness for the State, during custodial interrogation was made voluntarily and understandingly. If the presiding judge determines that the statement was not voluntarily and understandingly made, he will make his findings of fact and conclusions and enter an order vacating the judgment appealed from, setting aside the verdict, and granting defendant a new trial. If the presiding judge determines by the preponderance of the evidence that the statement of the defendant was made voluntarily and understandingly, he will make his findings of fact and conclusions, and order commitment to issue in accordance with the judgment appealed from and entered on 28 March 1977.
No error in the trial except on the issue of whether defendant’s custodial statement was voluntary.
Remanded with instructions.
Chief Judge BROCK and Judge HEDRICK concur.