In Russell v. State, 694 S.W.2d 207 (Tex. App.--Houston 1st Dist. 1985), aff'd, 749 S.W.2d 77 (Tex. Crim. App. 1988), a defense expert testified that the defendant was legally insane. This witness was the only expert to testify at the trial. The trial court later instructed the jury: "You are not bound by the testimony offered by a witness qualified as an expert. You may give it the weight to which you find it is entitled and may weigh such testimony with all other evidence offered in this case." Russell, 694 S.W.2d at 209. The court of appeals concluded that this instruction was a comment on the weight of the evidence, citing opinions in which similar instructions regarding expert testimony had been held improper. See id. (citing Florio v. State, 532 S.W.2d 614, 618 (Tex. Crim. App. 1976); Simmons v. State, 504 S.W.2d 465, 474 (Tex. Crim. App. 1974); Clark v. State, 500 S.W.2d 107, 111 (Tex. Crim. App. 1973)). The court observed, "The only defensive factual issue in the instant case was the question of insanity, and the instruction given commented subtly but adversely on the weight of the psychologist's testimony." Russell, 694 S.W.2d at 210. The court of criminal appeals agreed. "When a judge, in his charge to the jury, suggests that certain evidence is true or untrue, that is a comment on the weight of the evidence." Russell v. State, 749 S.W.2d 77, 78 (Tex. Crim. App. 1988). "In determining whether an instruction is a comment on the weight of the evidence, the courts have seen fit to assess the probable effect of the instruction on the jury in the context in which it was given." Id. at 79. The court concluded that the instruction, while neutral on its face, "had the obvious effect of singling out the expert's testimony" and had the effect of "leading the jury to believe that there was more question as to the credibility of the expert . . . than as to that of the other witnesses." Russell, 749 S.W.2d at 79-80.