Weighing the admissibility of fMRI technology under FRE 403: for the law, fMRI changes everything--and nothing.

AuthorAmirian, Justin
PositionIII. fMRI Under 403 B. Unfair Prejudice: Will the Jury Overvalue This Evidence? Through Conclusion, with footnotes, p. 743-770 - Functional magnetic resonance imaging; Federal Rules of Evidence
  1. Unfair Prejudice: Will the Jury Overvalue This Evidence?

    The first factor that must be weighed against the potential probative value of fMRI technology is its potential for unfair prejudice. (208) Relevant and probative evidence can be barred from admission if the jury would accord such evidence with weight disproportionate to its objective value. (209) Fear of jury overvaluation lies at the heart of much of the exclusion of admittedly relevant evidence, especially expert testimony. (210) However, evidence shows that people do not overvalue neuroscientific images. (211) On the other hand, jurors have been shown in fact to overvalue other types of evidence that are heavily relied upon, especially eyewitness testimony and forensic individualization (including DNA profiling). (212) This Part examines jurors' views of this technology in more depth.

    1. Jurors Will Not Overvalue Neuroimaging Evidence

      Initial scholarship gave credence to the idea that people were overly swayed by neuroscientific explanations and imagery. (213) Those who claim that neuroscientific evidence would have an undue influence on jury members pointed to a "Christmas tree phenomenon," (214) in that juries would be excessively persuaded by such images because they would be presented in the form of beautiful graphs with many bright colors. (215) These claims began even before the advent of fMRI technology. (216) Several studies outlined below have attempted to show how fMRI imaging would engender unfair prejudice. Almost all of these studies, however, suffer from various external and construct validity problems, (217) and none of them found the undue prejudice they sought.

      1. Gurley & Marcus (2008)

        An early study, conducted by Jessica R. Gurley and David K. Marcus, contended that jurors were more likely to return a result of "not guilty by reason of insanity" when presented with structural images of brain damage to defendants. (218) There are several reasons why this study is not applicable to fMRI lie detection. First, the experiment uses structural images, which depicts the brain at rest, (219) as opposed to the functional time-lapse images that fMRI provides when subjecting subjects to tasks, which is the subject of this Note. Second, the experiment failed to dissociate the brain images from the expert testimony; (220) thus, the question of whether it was the testimony or the images that produced the effect cannot be determined. (221)

      2. Weis berg et al. (2008)

        Another study, conducted by Deena S. Weisberg et al., asserted that people were more likely to believe explanations of events when they included neuroscientific language than the same explanations without such language. (222) However, the authors themselves recognized the major limitation of their findings, stating, "people may be responding to some more general property of the neuroscience information." (223) Most importantly, this study did not even measure the effect of brain images. (224) Further, subjects were not tested in a legal setting. (225)

      3. McCabe & Castel (2008)

        A third study, conducted by David P. McCabe and Alan D. Castel, argued that neuroscientific explanations were more influential when accompanied by brain images than when accompanied by bar graphs. (226) There were several problems with these results. First, subjects were asked to compare articles with brain images in each part of the experiment; there was no control condition in which a subject was asked to evaluate the article without a brain image altogether. (227)

        Second, much like the pitfall in the Gurley and Marcus study, the neuroscience language contained in the study likely already influenced subjects; (228) this Note is concerned with the effect of imaging. Moreover, critics argue that the images themselves weren't equivalent to each other. (229) Additionally, this experiment was not conducted in a legal setting. (230) Perhaps most importantly, when the raw data from this experiment and an attempted replication of it were combined, other researchers suggested that McCabe and Castel's purported conclusions were unsubstantiated. (231) That is, when other experimenters attempted to replicate the study's results, they instead found that the brain image exerted "little to no independent influence on juror verdicts." (232)

      4. McCabe et al. (2011)

        A fourth study, conducted by David P. McCabe et al., suggested that verbally offered fMRI lie detection evidence was more influential than lie detection evidence yielded from polygraph or thermal facial imaging technology offered in the same form. (233) This experiment's major shortcoming is that it fails to compare the effect of such verbal evidence with the effect of neuroimages (234) : verbal neuroscientific evidence is already permissible from expert witnesses in criminal cases. (235) Much like the limitation of the Weisberg et al. experiment, this study does not measure the effect of fMRI imaging. Of further note, this influence was negated when the technology's scientific validity was called into question within the experiment's fact pattern. (236)

      5. Greene & Cahill (2012)

        Another study, conducted by Edith Greene and Brian S. Cahill, argued that mock jurors were less likely to recommend a sentence of death for defendants at high risk of future dangerousness when given neuropsychological and neuroimaging evidence than when they were given neither. (237) However, visual representations of brain abnormalities did not have a more profound impact on jurors' decisions than neuropsychological testing results alone. (238) The authors suggested that any additional information may have affected the jurors decisions. (239) According to these scholars, "[w]hen [brain scans] do have an impact ... it is no greater than the impact of neuropsychological testing data that have been available for many decades." (240)

      6. Schweitzer et al. (2011)

        The most compelling study exploring the undue influence of neuroimagery found that neuroimagery did not affect jurors' judgments any more than verbal neuroscience-based testimony. (241) Several scholars understood the shortcomings of the aforementioned experiments, and undertook to try to expand or replicate them. (242) The four experiments within the study were designed to account for all of the variables that may have confounded the results of the aforementioned studies. (243) "In each successive experiment[,] the pressures on mock jurors to find guilt [were reduced] (thus potentially liberating them to be increasingly open to influence from the neuroimage evidence)." (244) Even though most of the authors of this study expected these images to unduly influence the mock jurors, (245) they concluded, "neuroimages had no especially potent or consistent impact on verdicts or sentences." (246) Describing this turn of events, another scholar stated, "[g]iven the visual appeal of images and their high-tech origins, the idea that they are inordinately persuasive is plausible. This a priori plausibility may have reduced scrutiny of the experimental designs and results that seem to support it." (247)

    2. Jurors Currently Overvalue Other Types of Evidence

      Jurors currently ascribe more weight than they should to certain kinds of admissible evidence based on that evidence's lack of objective value. As explained in the sections below, eyewitness testimony is notoriously unreliable, and yet it is continuously admitted, and strongly relied upon by jurors. Jurors also award excessive weight to forensic evidence, such as fingerprint and DNA evidence.

      1. Eyewitness Testimony

        Empirical research has effectively established that eyewitness testimony is unreliable. (248) Humans have limited cognitive capacities and are subject to biases and limitations, (249) including, importantly, those of memory and perception, (250) which lead them to be poor eyewitnesses. (251) Among other findings, studies have shown that human memory is malleable and rather ephemeral; (252) people are far better at recognizing the faces of people in their own race than they are those of a different race, (253) and a witness' confidence has little to no correlation with the accuracy of his or her testimony. (254) Jurors have very little awareness of these findings, despite the fact that they have been widely established for some period of time. (255) Perhaps most importantly, most people have very little understanding of the stages and faults of human memory storage and recall, (256) leading them to grossly overestimate a witness' ability to retain memories. (257) Even judges and attorneys themselves are not completely familiar with the shortcomings of eyewitness testimony. (258) Given the shortcomings in eyewitness testimony, and the lack of general awareness of those shortcomings, jurors tend to overvalue the intrinsic worth of such evidence. (259) Jurors place more weight on eyewitness testimony than on other types of evidence, and are substantially more likely to convict defendants when they hear such testimony than when none is available. (260) Before the development of forensic DNA testing, mistaken eyewitness identifications were responsible for the convictions of more innocent persons than any other combination of factors. (261) More recent studies of conviction reversals due to DNA testing indicate that a significant percentage of these reversals involved an eyewitness identification that turned out to false (262)--in some studies, as much as eighty-five percent (263)--making eyewitness testimony the "single greatest cause of wrongful convictions in this country." (264) For this reason, courts have increasingly permitted expert testimony that addresses the inaccuracy of eyewitness testimony, human memory, and false confessions. (265)

      2. Forensic Evidence

        Forensic science is continuously admitted under Daubert and FRE 702 with very little hesitation, despite its deficiencies and lack of scientific validity. (266) Forensic individualization methods, most notably...

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