dissenting.
Appellant, after having been denied a competency hearing by the trial judge, the Honorable David Walker, was tried on a murder indictment alleging the conduct to have occurred on the 12th of November, 1987. The trial ended on September 8, 1988, with the jury assessing punishment at 99 years imprisonment in the Texas Department of Corrections and a $5,000.00 fine. On direct appeal, in an unpublished opinion on January 24, 1990, the court of appeals abated the appeal and remanded the case to the trial court for a jury trial on the issue of competency to stand trial. See Barber v. State, 737 S.W.2d 824 (Tex.Cr.App.1987), cert. den., 489 U.S. 1091, 109 S.Ct. 1559, 103 L.Ed.2d 861 (1989).
Introduction of evidence in the competency hearing began on April 9, 1990 and continued until April 12, 1990; however, after several hours of deliberation, the jury was unable to reach a verdict and a mistrial was declared.
On April 30, 1990, evidence was presented to a new jury and on May 2, 1990, the jury found that the defendant was competent at the time he was tried on the indictment in 1988.
After the court of appeals affirmed appellant’s conviction, we granted appellant’s petition for discretionary review on three grounds of review. The majority has found that we improvidently granted grounds one and three for review and has overruled ground of review two. I dissent to this court’s determination that ground of review one was improvidently granted and that ground of review two should be overruled.
During the competency hearing at the behest of the prosecuting attorney, Judge David Walker, the presiding judge who had denied the defendant’s motion for a competency hearing in 1988 and who presided during that part of the proceedings dealing with guilt/innocence and punishment, testified as a witness. Judge Walker testified, in part, as follows:
Q. ... based upon your observations of [the defendant] — how would you characterize his understanding of the proceedings?
A. I think he understood everything that went on ... he asked intelligent questions, and he responded to what I did intelligently so, you know, there was just no opinion I could come up with except that he understood what was going on ... [a]nd he was competent.
Judge Walker further testified that “I never, in my opinion, saw anything really that [the defendant] said or acted during the *172trial or before the trial that indicated he was not competent.” In response to questioning concerning the defendant’s actions in conducting portions of his own trial, Judge Walker testified as follows:
Q. ... Did his questions indicate a lack of touch with reality or that he was having any kind of delusions or anything of that nature?
A. Absolutely not.
Q. ... is there anything in regard to the questioning of the witnesses that sticks out in your mind that indicates that Mr. Hensarling was not rational or didn’t understand what was going on or didn’t understand what the witness was saying?
A. Absolutely not.
When questioned about his decision not to empanel a jury to determine the issue of the defendant’s competency, Judge Walker testified as follows:
Q. And you did not feel like that it should be submitted to a jury as to whether or not he was competent?
A. That’s right. That’s right. And as I recall even Mr. Hensarling wanted to go ahead and go to trial, too, after we’d gotten that far.
In ground of review number two, appellant complains that Judge Walker was disqualified as a witness under Texas Rule of Criminal Evidence 605. The majority holds that Rule 605 is inapplicable to Judge Walker’s testimony because, they reason, the competency hearing is a different “proceeding” than the trial on the merits and Rule 605 only prevents the judge from stepping down from the bench and testifying in a proceeding over which he is currently presiding.
The majority’s view fails to recognize that a competency hearing is part of the same criminal proceeding as the trial on the merits. A competency hearing has been recognized as “ancillary to the main criminal proceeding” and likened to hearings on motions to suppress evidence and motions to quash an indictment. Jackson v. State, 548 S.W.2d 685, 690 (Tex.Cr.App.1977); see also Arnold v. State, 719 S.W.2d 590, 593 (Tex.Cr.App.1986), overruled on other grounds, Meraz v. State, 785 S.W.2d 146, 155 (Tex.Cr.App.1990). In fact, a defendant cannot directly appeal issues raised in a competency hearing, but must wait and raise those issues in an appeal on the trial on the merits. Jackson, 548 S.W.2d at 690. As noted in Arnold, a competency hearing is “part of a criminal case ... [b]ut for the criminal offense, the competency provisions of Art. 46.02 V.A.C.C.P., are not applicable.” Arnold, 719 S.W.2d at 592, n. 1. Here, Judge Walker was the presiding judge during the guilt/innocence and punishment portions of this criminal proceeding. He should not be allowed to testify under Rule 605 in a hearing in the same criminal proceeding. By doing so, he places his “seal of approval” on the side of the state.
It is not uncommon for more than one judge to preside over various portions of a single criminal proceeding. The majority’s interpretation of Rule 605 would tolerate the testimony of any number of judges who had presided over previous portions of a trial as to their opinion of facts related to issues on which they had previously ruled, regardless of whether or not a new jury were empaneled for purposes of the subsequent proceeding.
In ground of review one, appellant complains that his constitutionally protected right to due process was violated in that the judgment of competency, being based upon the testimony of Judge Walker, was manifestly unjust.1 Although both appellant and the state fully briefed the issue of whether it was fundamental error to allow the testimony of Judge Walker, the court of appeals, relying on the failure of appellant to preserve error, did not address the issue. However, the testimony of Judge Walker amounted to fundamental error of the nature that requires review even in the absence of an objection at trial and accord*173ingly, the court of appeals should have addressed the ground of error.
This court has recognized that once jurisdiction attaches, this and other appellate courts in Texas have a “broad scope of review and discretion,” and may review issues of unassigned error. Carter v. State, 656 S.W.2d 468, 469 (Tex.Cr.App.1983); see also Moreno v. State, 114 Tex.Cr.R. 559, 26 S.W.2d 652 (Tex.Cr.App.1930) (Holding that “this court can only sit in review upon matters of error either fundamental or which are properly raised upon the trial”). Certain due process violations have been recognized as so fundamental as to require review by an appellate court, even in the absence of objection during trial or a ground of error raised on appeal. Skelton v. State2, 655 S.W.2d 302, 304 (Tex.App.—Tyler 1983, pet. ref'd); see also Howeth v. State3, 645 S.W.2d 787, 788 (Tex.Cr.App.1983). This court should review appellant’s ground of review one although not objected to at trial since the alleged error is such that it calls into question whether the accused received a fair and impartial trial and “implicates the due course of law clause of the Texas Constitution.” Howeth, supra; see also Skelton, supra. The testimony of the trial judge for the state in a subsequent hearing in the same criminal proceeding in which the judge had earlier presided also implicates due process concerns. Brown v. Lynaugh, 843 F.2d 849 (5th Cir.1988).
In Brown v. Lynaugh, the Fifth Circuit addressed whether the state’s use of the presiding judge as a witness amounted to a denial of the defendant’s due process rights.4 Id. During proceedings relating to a motion for new trial following the conviction of a felony, the defendant, Brown, bolted from the courtroom and escaped. Id. The subsequent trial for the felony of escape from custody was held before Judge Walter Smith, the same judge who had presided over the proceedings in which the defendant had escaped. The state called Judge Smith as a witness, whereupon he testified as to facts establishing essential elements of the offense of escape.5 In holding that Judge Smith’s testimony denied Brown a fair trial, the Fifth Circuit stated that:
It is difficult to see how the neutral role of the court could be more compromised, or more blurred with the prosecutor’s role than when the judge serves as a witness for the state. One of the fundamental tenants of our jury system is a strong trial judge. Under that system, the trial judge is properly presented to the jury as the ultimate authority figure, imbued with unquestioned respectability and impartiality. For this reason, juries *174are traditionally ‘highly sensitive to every utterance of the trial judge.’
Id. at 850 (citations omitted). The Fifth Circuit concluded that the state’s use of the trial judge’s testimony to establish essential elements of the subject offense deprived the defendant of his right to a fair trial.
Although Judge Walker did not preside over the competency hearing at which he testified, the same concerns expressed by the Fifth Circuit in Brown are nevertheless present. Judge Walker was identified in the competency hearing as the presiding judge during the guilt/innocence and punishment portions of the trial. It was clear to the jury that Judge Walker would in fact be presiding over the competency proceedings but for the fact that he was now a “Senior Judge.” Judge Walker was presented to the jury as an ultimate and impartial authority on the competency of the defendant to stand trial. He was presented as “the ultimate authority figure, imbued with unquestioned respectability and impartiality.” As stated in Brown, “it is difficult to see how the role of the court could be more compromised” than here where the judge who presided in the guilt/innocence and punishment portions of the same proceedings is now aligned with the state.6
In Brown, the Fifth Circuit found that due process was denied where the judge testified as to facts constituting elements of the subject offense. Here, Judge Walker testified as to his opinion about the competency of the defendant. The denial of due process is even more disturbing here than in Brown, as opinion testimony is less susceptible to scrutiny than testimony pertaining to verifiable facts. Further, Judge Walker, whose ruling on the competency hearing had been overturned, was not an impartial observer on this issue. To allow the trial judge to testify in a competency hearing as to his opinion of the competency of a defendant when that same judge had previously ruled in error that a competency hearing on this defendant’s competency to stand trial was not called for is so contrary to the concept of “fundamental fairness” as to amount to a denial of due process.
For the reasons herein stated I respectfully dissent. I would reverse the decision of the court of appeals on either ground of review one or ground of review two and remand this cause for a new hearing on the competency of appellant to stand trial.
BAIRD and OVERSTREET, JJ., join.. In the court of appeals, appellant claimed that it was fundamental error for a trial judge in a subsequent competency hearing to testify as to his lay opinion and his opinion of the law on an ultimate issue.
. In Skelton v. State, the trial court struck the testimony of three of the witnesses for the defense who testified as to the defendant’s character and reputation. 655 S.W.2d at 302. Although the defendant did not object during trial or raise the error on appeal, the court of appeals stated that ”[w]here a defendant has been deprived of due process under the state and federal constitutions, indeed it is our constitutional duty to take appropriate action to enforce such constitutional protections." Id. at 304. I would note that this court has favorably cited Skelton for its definition of "due process.” Meraz v. State, 714 S.W.2d 108, 113 (Tex.Cr.App.1986).
. In Howeth v. State, this court granted the appellant’s petition for discretionary review to address the sufficiency of the evidence to support conviction. 645 S.W.2d at 788. We held that a sufficiency of the evidence issue "implicates the Fourteenth Amendment to the Constitution of the United States and the due course of law clause of the Texas Constitution” and therefore we would "ex mero motu or ex proprio motu or sua sponte" address the issue. This court found that "error of a fundamental nature exist[ed]” and reversed the decision of the court of appeals. Id.
. At the time of the proceedings in the state trial court in Brown the controlling statute, Article 38.13 of the Texas Code of Criminal Procedure, provided that the trial judge could be called as a witness for the state or the defense. This article was repealed effective September 1, 1986. In rendering its decision in Brown, the Fifth Circuit found Article 38.13 unconstitutional as applied in that case. Brown, 843 F.2d at 851. As noted above, Tex.R.Crim.Evid. 605 had not been enacted at the time of the applicable proceedings in Brown.
. Judge Smith testified that (1) he was the presiding judge at the time of the escape; (2) he recognized the defendant; (3) Brown was previously convicted and sentenced on a separate offense; (4) he saw Brown escape from the courtroom; and (5) Brown was in custody when he escaped.
. Aggravating the situation, the state also called Judge J.B. Goodwin as a witness. Judge Goodwin had been the prosecuting attorney during the guilt/innocence and punishment portions of the proceedings. Since that time he had been elevated to the bench to succeed Judge Walker.