In People v. Wilson, 133 AD2d 179, 518 NYS2d 690 [1987], the Appellate Division, Second Department, reversed defendant's conviction, holding that the trial court erred in allowing a forensic psychologist to render an expert opinion as to the psychological state of defendant where no clinical examination of the defendant by the expert had been undertaken, but where the expert observed defendant's courtroom testimony.

The Court held that "while the admissibility of expert testimony is generally a determination which rests in the sound discretion of the trial court (see, e.g., People v. Cronin, 60 NY2d 430, 458 NE2d 351, 470 NYS2d 110), it is nevertheless incumbent upon the proponent of such testimony to lay a proper foundation establishing that the processes and methods employed by the expert in formulating his or her opinions adhere to accepted standards of reliability within the field (see, People v. Brown, 67 NY2d 555, 496 NE2d 663, 505 NYS2d 574 cert denied [479] US [1093], 107 S Ct 1307, 94 L Ed 2d 161; People v. Hughes, 59 NY2d 523, 537, 453 NE2d 484, 466 NYS2d 255; People v. Leone, 25 NY2d 511, 255 NE2d 696, 307 NYS2d 430)." (Id. at 183.)

The Court found that such testimony is impermissible, not only because there is no evidence to "establish that a diagnosis premised upon courtroom observation has attained any measure of scientific recognition as a reliable substitute for a clinically derived evaluation of a subject's mental processes" (id.), but also because "a diagnostic technique which features courtroom observation of trial testimony as its principal evaluative tool, necessarily requires the nonexamining medical expert to comment extensively upon the defendant's testimony concerning the ultimate issue to be resolved in the case, thereby potentially impinging upon the jury's role as trier of fact." (Id. at 184.)