OPINION OF THE COURT
JONES, Senior Judge:We must determine whether appellant’s lack of mental responsibility during the course of the Article 32, UCMJ, 10 U.S.C.A. § 832, investigation requires us to set aside the findings of guilty and the sentence. The appellant was sane at the time of the offenses and competent at the time of trial, and counsel assures us that the appellant is competent during the course of these proceedings.
The appellant was charged with two aggravated assaults on his squad leader and with wrongfully disposing of military property of the United States in violation of Articles 128 and 108, Uniform Code of Military Justice, 10 U.S.C. §§ 928 and 908. The general court-martial with members sentenced him to be confined at hard labor for one year and to forfeit $250 pay per month for eight months. The convening authority approved the sentence.
At the initial session of the Article 32, UCMJ, investigation, the appellant’s civilian defense counsel requested a psychiatric evaluation of appellant on the ground that appellant was not able to participate in his defense. The appellant was evaluated briefly at the Air Force hospital in Alaska but, because appellant had attempted to escape from his guards, the commander denied permission for the appellant to be taken off post to be evaluated by a civilian psychiatrist. The civilian psychiatrist was permitted to evaluate appellant at the local post stockade but this did not occur until after the investigation was completed.
The Article 32, UCMJ, investigating officer determined that the appellant was competent to proceed with the investigation based upon the investigating officer’s personal observation of appellant, the report of the Air Force doctor who examined him briefly and reports of psychiatric evaluations 2-3 months earlier at the Air Force hospital in Alaska and at Letterman Army Medical Center in San Francisco. The investigating officer recommended trial by general court-martial and the convening authority so referred the charges.
In a preliminary session of the trial pursuant to Article 39(a), UCMJ, the appellant sought a new Article 32 investigation on several grounds, including one concerning *914his competency at the time of the investigation. The military judge denied the motion for a new investigation but, after the presentation of evidence, ordered a sanity board inquiry. The information furnishing the basis for ordering the inquiry should have alerted the judge to the need to defer his ruling on the request for a new Article 32 investigation.
When the court-martial reconvened several weeks later at another Article 39(a), UCMJ, session, a new military judge was presiding. He announced that the rulings of the military judge at the earlier session were the law of the case and he effectively precluded counsel from any further litigation of those issues by allowing only motions that were not heard and decided previously.
The issue of mental responsibility was litigated fully as part of the case on the merits. The members of the sanity board were unanimous in their conclusion that appellant was sane at the time of the offenses and was competent to stand trial. Two members of the sanity board testified, however, that during the period of the Article 32, UCMJ investigation the appellant was suffering from a mental illness that made him not responsible for his thoughts and behavior.1 The third member of the board did not testify.
A civilian psychiatrist presented by the defense stated that appellant was acutely psychotic and thus unable to conform his conduct to the law during the period of the investigation and that there was a “great probability” that he was unable to conform his conduct to the law at the time of the offenses. All psychiatrists were therefore in agreement as to appellant’s lack of competence during the Article 32, UCMJ investigation.
The appellant, in this appeal pursuant to Article 66, UCMJ, 10 U.S.C.A. § 866, has not raised the issue of mental responsibility at the time of the offenses or competence to stand trial but instead has focused upon his incompetence during the Article 32, UCMJ investigation. He argues that reversal is required as it was error per se to proceed with the investigation when he, the accused, was not competent. When this “substantial and fundamental pre-trial right” was violated and when appellant made a timely demand for compliance as he did here, appellant asserts that the military judge had no choice but to grant the motion for a new Article 32, UCMJ, investigation. In support of his position, appellant has called our attention to Glasser v. United States, 315 U.S. 60, 62 S.Ct. 457, 86 L.Ed. 680 (1942) and United States v. Mickel, 9 U.S.C.M.A. 324, 26 C.M.R. 104 (1958).
We agree with appellant that the ability to understand the proceedings and to participate in his defense is a substantial pretrial right and that when the appellant was required to undergo an Article 32 investigation while not mentally competent he was denied that right. The military judge erred in not reconsidering the motion and granting a new Article 32, UCMJ, investigation. To quote from Mickel:
[I]f an accused is deprived of a substantial pretrial right, on timely objection he is entitled to judicial enforcement of his right, without regard to whether such enforcement will benefit him at the trial. 26 C.M.R. at 107.
The Court of Military Appeals reaffirmed and extended this position in United States v. Donaldson, 23 U.S.C.M.A. 293, 49 C.M.R. 542 (1975), United States v. Chestnut, 2 M.J. 84, 85 n.4 (C.M.A. 1976), and United States v. Chuculate, 5 M.J. 143 (C.M.A. 1978).
In view of Mickel, Donaldson, Chestnut, and Chuculate this Court has no choice but to set aside the findings and sentence and authorize a new Article 32, UCMJ investigation and if then appropriate, a rehearing. *915We are compelled to take this action even though we find no reasonable possibility of prejudice to appellant resulting from the conduct of the Article 32, UCMJ investigation during the period appellant was incompetent.2 Appellant was ably represented by counsel at every phase of the proceedings. We have been unable to perceive nor has appellant been able to point to one single thing which could have been done but was not or would have been done differently had he been able to cooperate with his counsel during the investigation.
The appellant also asserts that a new Article 32 investigation should have been granted because the investigating officer departed from his judicial role in violation of United States v. Payne, 3 M.J. 354 (C.M.A. 1971). This issue was litigated thoroughly. The presumption of prejudice arising from ex parte communications by the investigating officer was dispelled by the testimony of the witnesses, with one exception. That exception concerned the investigating officer’s conversation with appellant’s battalion commander concerning the sanity issue. The other communications related to administrative and procedural matters. The conversation with the commander touched on the evaluation by the Air Force psychiatrist whose report was admitted in evidence at the investigation. The error, if any, arising from that conversation merged into and became a part of the error by the military judge in not granting a new Article 32 investigation because of the lack of competence of the appellant at the time of the investigation.
The findings of guilty and the sentence are set aside. A new Article 32, UCMJ investigation and if appropriate a rehearing may be ordered by the same or a different convening authority.
GARN, Judge, concurs.. We equate this to an inability to understand the proceedings or cooperate with his defense counsel.
. We respectfully request the Court of Military Appeals to reexamine its position in Donaldson, Chestnut, and Chuculate, to the effect that an accused is entitled to the enforcement of a pretrial right without regard to whether such enforcement will benefit him at trial.
The rule announced in Mickel was based upon Glasser v. United States, 315 U.S. 60, 62 S.Ct. 457, 86 L.Ed. 680 (1942), a case involving the denial of the right to counsel at trial. Mickel also involved the denial of a right to counsel, but at a pretrial phase (Article 32 investigation) rather than at trial. A violation of the right to counsel is of such magnitude that it can never be harmless, Holloway v. Arkansas, 435 U.S. 475, 98 S.Ct. 1173, 55 L.Ed.2d 426 (1978), and no test for prejudice will be made. Glasser v. United States, supra. But see Moore v. Illinois, 434 U.S. 220, 98 S.Ct. 458, 54 L.Ed.2d 424 (1977).
The rights involved in Donaldson, Chestnut, and Chuculate are of lesser stature than the right to counsel and should be treated in the same manner as those constitutional errors tested under the harmless error rule. See Chapman v. California, 386 U.S. 18, 87 S.Ct. 824, 17 L.Ed.2d 705 (1967); Fahy v. Connecticut, 375 U.S. 85, 84 S.Ct. 229, 11 L.Ed.2d 171 (1963); Moore v. Illinois, supra.
The Court of Military Appeals followed the “test for prejudice” standard in United States v. Cunningham, 12 U.S.C.M.A. 402, 30 C.M.R. 402 (1961), and United States v. Lopez, 20 U.S.C.M.A. 76, 42 C.M.R. 268 (1970), cases involving objections raised at trial to a defective Article 32, UCMJ investigation (accuser was investigating officer; investigating officer had conducted an inquiry into the incident previously). The Court stated that defects in the pretrial investigation must be measured by the test of specific prejudice. Similarly in United States v. Payne, 3 M.J. 354 (C.M.A. 1977), the Court applied a test for prejudice to the improper actions of the Article 32 investigating officer.
We believe the rule in Mickel should be limited to the denial of the right to counsel. The instant case did not involve that right. Cf. Pate v. Robinson, 383 U.S. 375, 86 S.Ct. 836, 15 L.Ed.2d 815 (1966). We believe a test for prejudice is proper.