By Heidi Schumann, ACLR Featured Online Contributor

Imagine a defendant on the witness stand testifying that he had no involvement in the crime that he is accused of. After the defendant finishes his testimony, his attorney calls another witness: an expert in a procedure called fMRI.1 He testifies that he used this method to determine that the defendant is in fact telling the truth when he denied involvement in the crime. The expert testifies that he used the fMRI procedure prior to this trial to determine if the defendant’s testimony was true. He determined through this procedure that the statements were in fact true, and those statements are the same as the defendant’s testimony in court.  These are the only two witnesses for the defense, and after the expert’s testimony the defense rests. At the close of trial the jurors are read their instructions and retire to the jury room to deliberate. The jury now has before them two credibility assessments to make, first the credibility of the defendant and second the credibility of the expert and his technique. Have we added to the work of the jury or subtracted from it? In either case, have we aided in justice or supplanted the purpose of the jury with a scientific test? In the past decade, several defendants have sought to admit this type of evidence in both criminal and civil suits. No court has yet let the neurological evidence in, but proponents for the test are continuing to develop the technology and push for its admission.2

To date, the neurological tests that have been developed to determine whether someone is telling the truth have been barred from admission on several occasions.3 One of the more influential cases on the issue is United States v. Semrau.4 In that case the defense tried to admit an expert who would testify that the defendant, Dr. Semrau, was telling the truth when he denied the allegations against him.5 In particular, Dr. Semrau attempted to admit the results of an fMRI lie detection test.6 The fMRI lie detection test works by comparing images of the brain from a control period (often times one in which a person is forced to make both true statements and statements which are lies) to scans taken of the brain when the defendant is answering questions regarding his or her alleged participation in the crime.7 Based on the images of the brain, and in particular the oxygen levels of the areas of the brain, one can determine if a person is relating something that he or she knows or if he or she is fabricating a story—that is, whether a person is lying or telling the truth.8

Dr. Laken, who was the proposed expert witness in Semrau, is the doctor who patented this test. At Dr. Semrau’s trial Dr. Laken testified that the test had only been performed in mock scenarios in which he had volunteers “steal” something (one example given was a watch) and performed the test based on these controlled scenarios.9 In his testimony at the trial, Dr. Laken testified that the accuracy of his test was between 86-97% accurate. This accuracy range was called into question, however, when on cross examination the opposing counsel questioned him about one published study in which the accuracy dropped to 71%. Dr. Laken also testified about certain factors, which could add to the inaccuracy of the test including, notably, brain fatigue, which could occur after only two rounds of questioning or because of a lack of sleep the night before questioning.10 An additional area of concern regarding the accuracy of the test is the frequency with which it produced a false positive, meaning the test indicated someone was lying when in fact he or she was telling the truth, was huge.11 In one study Dr. Laken testified that “nineteen out of twenty people that were telling the truth we would call liars.”12

At trial the court did not allow in the expert testimony, and the Sixth Circuit affirmed the lower court’s decision.13 The court’s reasoning in each of these cases is mostly focused on the reliability of the fMRI test because Dr. Laken had not (and the court implicitly argued could not) produce rates of error in real-world testing.  The court appropriately reinforced the necessity of such testing as a condition of admitting fMRI results in court when it observed that Dr. Laken provided no research which “demonstrate[ed] how the brain might respond to fMRI lie detection testing examining potential deception about real world, long-term conduct occurring several years before testing in which the subject faces extremely dire consequences (such as a prison sentence) if his answers are not believed.”14 The court also noted that while there was some peer reviews of Dr. Laken’s method, the scientific community had not adopted it as an accepted procedure.15 Several subsequent attempts by defendants to bring in this type of test have also been met with the same fate.16

However, many proponents of the test assert that the science is still in development and could with time be improved.17 Therefore, the hypothetical scenario mentioned above may be closer to reality within the next decade. If this scenario really did come true, how would this change courtrooms in the future, and are these changes for the better?

Some of the positive effects of inclusion of this type of evidence is that it will open up the ability of the defendant to testify on his or her own behalf. Very often defendants, in particular those with prior criminal history, are reluctant to take the stand. A common form of impeachment evidence is the use of the defendant’s prior criminal history, which can be introduced if a defendant chooses to testify.18 The fact that a scientific test has been performed regarding the defendant’s truthfulness in this case, could help counter the impeachment evidence and give some weight to the defendant’s testimony. Therefore, at least theoretically, having a test of truthfulness to back defendants up could induce more to take the stand. Admitting this test could allow more relevant evidence to come into the trial, and in this way, the test may truly help promote justice.

There is still concern that admitting an expert to opine on the truthfulness of a witness takes over a core function of the jury.19 One author theorizes that taking away this element of a jury’s decision making process could undermine that sovereign duty with negative consequences such as increased rate of jury nullification or the politicization of the jury.20 Another argument that has been made is that the jury would not be able to properly use or limit their use of the evidence because the science is too complex.21 At the moment, the science is not yet at a point in which it can predict to a reliable degree the truthfulness of a person’s statements. Yet, the conversation regarding the admissibility of such evidence is ripe. If there is a more accurate fact finder than the jury, what is the jury’s continued function in the legal system? Does the jury do something more than just fact-find in reaching a verdict? Furthermore, should the defendant’s hope of being able to present evidence of his innocence, perhaps the only piece that he could present, be excluded in order to maintain the traditional role of the jury? The answer to these questions is inseparably tied to the process, evaluation, and accuracy of the fMRI test and similar technologies. Yet, if this technology could help defendants establish their innocence, especially those defendants who as a result of prior criminal history have significant concerns about testifying in their own defense, then the courts must begin to consider this evidence and allow for its inclusion.  To do otherwise would give the appearance of preferring to maintain “the system” as it is, rather than a system of justice.