concurring.
I wholly concur in the majority opinion, but I am compelled to add further explanation for the result. Although the trial occurred approximately one month before Tenn.R.Crim.P. 33(f) (the thirteenth juror rule) became effective, the defendant’s motion for new trial was filed and the hearing thereon was held after its effective date. The motion raised the issue of the substitute judge’s (trial judge’s) inability to exercise his function as the thirteenth juror. Under these circumstances, State v. Enochs, 823 S.W.2d 539 (Tenn.1991) indicates that the rule would apply in this case. In applying the thirteenth juror rule, the trial judge was to weigh the evidence, including the assessment of witness credibility. See Curran v. State, 157 Tenn. 7, 4 S.W.2d 957, 958 (1928); State v. Johnson, 692 S.W.2d 412, 414 (Tenn.1985) (Drowota dissenting).
In this case, the primary witness for the state was David Harvey, who testified that the defendant was the leader in the plan to kill the deceased and that both he and she shot him. The defendant’s proof was to *915the effect that, although the defendant was present, Harvey acted alone in killing the deceased without the defendant’s knowledge that the offenses were going to occur. Thus, Harvey was an accomplice under the state’s theory and the sole perpetrator under the defendant’s theory. Simply put, Harvey’s credibility was crucial to the state’s case. However, the trial judge was not presiding during any of the direct examination and the large majority of the cross-examination of Harvey.
The extent to which a substitute judge must familiarize him or herself with the record of the trial may depend upon the issue in question. As stated in United States v. Larios, 640 F.2d 938, 943 (9th Cir.1981), the amount of record review required “varies with the facts of each case, the more the case depends on the credibility, and especially the demeanor, of the witnesses, the more a judge needs to do to become adequately familiar with it.”
Obviously, credibility involves more than demeanor in that it “apprehends the overall evaluation of testimony in the light of its rationality or internal consistency and the manner in which it hangs together with other evidence.” Carbo v. United States, 314 F.2d 718, 749 (9th Cir.1963). As Carbo reflects, the other evidence which corroborates the contested witness may be of such a nature and strength that a substitute judge in reading the record may determine that the other convincing evidence places the state’s case “safely beyond demeanor impeachment...” Id. at 750. In Carbo, the Ninth Circuit noted that the substitute judge spent three months studying the 7,500 pages of transcript and concluded that he was sufficiently familiar with the record to determine that the contested witnesses’ demeanor was not an issue. Id. at 749-750. However, in this case, as the majority opinion notes, the record does not reflect that the trial judge sufficiently certified that he familiarized himself with the record nor does it reflect that he, in fact, had such familiarity so as to act appropriately as the thirteenth juror.
Also, as Carbo indicates, the less convincing the corroborating evidence the more important “demeanor appears to loom in making the necessary credibility determinations.” 314 F.2d at 749. The corroborating evidence in this case falls far short of either excluding the legitimacy of the defendant’s theory or fully accrediting Harvey’s testimony in proving the state’s theory. Thus, we cannot, through a review of the record, conclude that Harvey’s demean- or on the witness stand was insignificant in assessing his credibility. Under the circumstances in this case, the trial judge could not properly approve the jury verdict, as is required, because of his inability to exercise his function as the thirteenth juror in weighing the evidence. It is for these reasons that a new trial is warranted. See Curran v. State, supra.