Cite as: 523 U. S. 303 (1998)
Opinion of the Court
cant interest of the accused. Here, the court members heard all the relevant details of the charged offense from the perspective of the accused, and the Rule did not preclude him from introducing any factual evidence.13 Rather, respondent was barred merely from introducing expert opinion testimony to bolster his own credibility. Moreover, in contrast to the rule at issue in Rock, Rule 707 did not prohibit respondent from testifying on his own behalf; he freely exercised his choice to convey his version of the facts to the court-martial members. We therefore cannot conclude that respondent's defense was significantly impaired by the exclusion of polygraph evidence. Rule 707 is thus constitutional under our precedents.
* * *
For the foregoing reasons, Military Rule of Evidence 707 does not unconstitutionally abridge the right to present a defense. The judgment of the Court of Appeals is reversed.
It is so ordered.
13 The dissent suggests, post, at 331, that polygraph results constitute "factual evidence." The raw results of a polygraph exam—the subject's pulse, respiration, and perspiration rates—may be factual data, but these are not introduced at trial, and even if they were, they would not be "facts" about the alleged crime at hand. Rather, the evidence introduced is the expert opinion testimony of the polygrapher about whether the subject was truthful or deceptive in answering questions about the alleged crime. A per se rule excluding polygraph results therefore does not prevent an accused—just as it did not prevent respondent here—from introducing factual evidence or testimony about the crime itself, such as alibi witness testimony, see ibid. For the same reasons, an expert polygrapher's interpretation of polygraph results is not evidence of " 'the accused's whole conduct,' " see post, at 336, to which Dean Wigmore referred. It is not evidence of the " 'accused's . . . conduct' " at all, much less "con-duct" concerning the actual crime at issue. It is merely the opinion of a witness with no knowledge about any of the facts surrounding the alleged crime, concerning whether the defendant spoke truthfully or deceptively on another occasion.
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