Daredevil’s many super powers include heightened hearing, which allows him to listen to another person’s heartbeat up to twenty feet away. This ability is highlighted throughout the Daredevil comic books and the recent Netflix series. According to the comics and Netflix series, Daredevil is able to “detect” when someone is lying by listening to heartbeat changes. Interestingly, Daredevil’s reliance on this technique is misplaced and peculiar where his alter ego Matt Murdock is a criminal defense attorney from a prestigious law school. This post briefly discusses the case law and science behind why Daredevil’s use of heartbeat lie detection is both scientifically and legally objectionable.
A 1923 case titled Frye v. U.S. discussed the “systolic blood pressure deception test,” a precursor to the polygraph test. The theory behind the test was a person’s blood pressure increases when he or she consciously attempts to deceive another person due to the conscious attempt to deceive and the fear of the lie being detected. In contrast, as the theory goes, when a person tells the truth there is no conscious effort to do so, which makes telling a truth spontaneous, without effort, and without a fear of detection. As a result, telling a truth would not raise a person’s blood pressure in the same way as conscious deception.
The theory behind polygraph testing is similar to the test discussed in Frye. Polygraphs measure a person’s physiological responses to stress or nervousness. These measurements include, “systolic blood pressure (the first and more rapidly variable number in the familiar blood pressure measurement of, for example, 125/75), heart rate, breathing rate, and skin sweatiness (measuring the electrical conductivity of skin, known as galvanic skin response).” The problem with inferring that physiological responses indicate deception is that, as stated by the American Psychological Association (APA), “There is no evidence that any pattern of physiological reactions is unique to deception.” The APA advises, “to remain skeptical about any conclusion wrung from a polygraph” where there is simply not enough plausible research to support the validity of such tests.
In Frye, the Court ultimately rejected introducing expert testimony about the test results into evidence because the science behind the test was not generally accepted in its particular scientific field. Most courts continued their skepticism of lie detection tests when applying the “general acceptance” rule in Frye and denied admission of such evidence.
The rule of “general acceptance” in Frye was eventually superseded 70 years later in Daubert v. Merrell Dow Pharmaceuticals, Inc. The expert testimony in Daubert differed from Frye where it was about whether a medication could cause birth defects. The Daubert Court determined that Rule 702 of the Federal Rules of Evidence ultimately controls expert testimony where a qualified expert may testify if the expert’s scientific knowledge would assist the fact finder in understanding a fact in issue at trial.” The Court noted that a trial judge acts as a gatekeeper under Rule 702 where he or she determines if the expert’s testimony is scientific knowledge and if the testimony is relevant to the fact in issue. To determine if a method or theory is scientific knowledge, a judge may consider a myriad of factors, including its error rates, whether a method or theory has been tested, peer-reviewed, published, or, as contemplated in Frye, generally accepted.
After the rule announced in Daubert, a majority of courts still excluded polygraph test results and testimony about those results. The U.S. Supreme Court acknowledged five years after Daubert, that “there is simply no consensus that polygraph evidence is reliable.” In New York, where Murdock practices law, polygraph evidence is generally inadmissible because it is insufficiently reliable.
Matt Murdock, as a criminal defense attorney, should know that his method of lie detection is dubious in the scientific community as well as generally inadmissible in court. Daredevil’s disregard for the legal and scientific understanding of lie detection adds a layer of complexity to his character if it is not understood as writer oversight. As a vigilante, he inherently disregards the law to seek justice. Daredevil’s use of heartbeat lie detection may inform the extent and fallibility of his vigilantism.
 Frye v. United States, 293 F. 1013, 1013 (D.C. Cir. 1923).
 Id. at 1014.
 Henry T. Greely & Judy Illes, Neuroscience-Based Lie Detection: The Urgent Need for Regulation, 33 Am. J.L. & Med. 377, 386 (2007).
 See James R. McCall, Misconceptions and Reevaluation-Polygraph Admissibility After Rock and Daubert, 1996 U. Ill. L. Rev. 363 (1996).
 Daubert v. Merrell Dow Pharm., Inc., 509 U.S. 579, 582, 113 S. Ct. 2786, 2791, 125 L. Ed. 2d 469 (1993).
 Id. at 2794.
 Id. at 2796.
 Id. at 2797.
 United States v. Scheffer, 523 U.S. 303, 309, 118 S. Ct. 1261, 1265, 140 L. Ed. 2d 413 (1998) (holding that a per se rule in the Military Rules of Evidences excluding polygraph evidence does not violate a defendant’s right to put on a defense).
 People v. Shedrick, 66 N.Y.2d 1015, 1018, 489 N.E.2d 1290, 1292 (1985)(holding the polygraph evidence is not sufficiently reliable to admit at trial); See also People v. De Lorenzo, 45 A.D.3d 1402, 1402, 845 N.Y.S.2d 652, 653 (2007)(holding that trial court did not error by denying a Frye hearing on polygraph evidence where defendant made no showing that consensus on reliability of polygraphs has changed since People v. Shedrick).