Frye v. United States

The ruling set a standard for the acceptance of expert testimony in court that, by the early 1970s, was adopted by almost all state and federal courts.

In 1923 James Alphonzo Frye appealed his conviction for second degree murder. Frye, who had confessed and later retracted his admission, had been prosecuted by the federal government and convicted by a jury sitting in a Washington, D.C. trial court. At trial, the court refused to let Frye introduce evidence about his truthfulness through a "systolic blood pressure deception test," a crude precursor to what is now popularly known as a lie detector or polygraph test. The court also refused to let Frye introduce an expert witness to testify about the deception test.

The sole basis of Frye's appeal was the failure of the trial court to admit the deception test. In a unanimous decision, the three-judge Court of Appeals of the District of Columbia ruled for the United States in a short opinion that became one of the most notorious opinions written by a federal appeals court.

In the opinion, written by Justice Van Orsdel, the court described how the machine operated and how, when attached to a subject, it supposedly could detect whether a subject was being deceptive. "It is asserted," said the court, "that blood pressure is influenced by change in the emotions of the witness, and that the systolic blood pressure rises are brought about by nervous impulses sent to the sympathetic branch of the autonomic nervous system." Frye argued that systolic blood pressure rose in a predictable curve when a subject was being deceptive and afraid that the falsehood could be detected. The curve, maintained Frye, corresponded "exactly to the struggle going on in the subject's mind, between fear and attempted control of that fear, as the examination touches the vital points in respect of which he is attempting to deceive the examiner."

The court characterized the information offered by Frye as a "theory" holding that "truth is spontaneous, and comes without conscious effort, while the utterance of a falsehood requires a conscious effort, which is reflected in the blood pressure." As there were no prior similar cases for use as guidance, the court was left to make up a rule on the admissibility in court of deception tests. Frye insisted that the deception test could be explained by a witness who was an expert in the field, but the court rejected this with these now-famous words:

Just when a scientific principle or discovery crosses the line between the experimental and demonstrable stages is difficult to define. Somewhere in this twilight zone the evidential force of the principle must be recognized, and while courts will go a long way in admitting expert testimony deduced from a well-recognized scientific principle or discovery, the thing from which the deduction is made must be sufficiently established to have gained general acceptance in the particular field in which it belongs.

In the court's opinion, the systolic blood pressure deception test had not gained enough "standing and scientific recognition among physiological and psychological authorities" to justify its admission as evidence in courts of law. The court approved of the exclusion of the deception test, and Frye's conviction was affirmed.