Reference Manual on Scientific Evidence Third Edition (2011) / Chapter Skim
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Reference Guide on Neuroscience--Henry T. Greely and Anthony D. Wagner
Reference Guide on Neuroscience--Henry T. Greely and Anthony D. Wagner
Pages 747-812
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contents I. Introduction, 749 II. The Human Brain, 749 A. Cells, 750 B. Brain Structure, 754 C. Some Aspects of How the Brain Works, 759 III.
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Possible rights against neuroscience evidence, 790 2. Possible rights to the creation or use of neuroscience evidence, 795 3.
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We know almost infinitely more than we did 30 years ago; however, we know almost n othing compared with what we are likely to know 30 years from now. The results of advances in understanding human brains -- and of the minds they generate -- are already beginning to appear in courtrooms.
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At a synapse, the two neurons will come within 2. The Society for Neuroscience, the very large scholarly society that covers a wide range of brain science, has published a brief and useful primer about the human brain called Brain Facts. The most recent edition, published in 2008, is available free at www.sfn.org/index.aspx?
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The electrical currents of neurons are more complicated. Molecules with a positive or negative electrical charge (ions)
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Figure 2. Synapse.
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Estimates of the number of cells in a human brain vary widely, from a few hundred billion to several trillion. These cells include those that make up blood vessels and various connective tissues in the brain, but most of them are specialized brain cells.
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We also, less fairly, ignore the central nervous system other than the brain, even though the spinal cord, in particular, plays an important role in modulating messages going into and coming out of the brain. The average adult human brain (Figure 3)
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More recent studies of patients with cerebellar damage and functional brain imaging studies of healthy individuals indicate that the cerebellum also plays a role in more cognitive functions, including supporting aspects of working memory, attention, and language. The cerebrum is the largest part of the human brain, making up about 85% of its volume.
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Thus, one could describe a particular region as lying in the left frontal lobe -- the frontal lobe of the left hemisphere. The surface of the cerebrum consists of the cortex, which is a sheet of gray matter a few millimeters thick.
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For most of us, these names will have no obvious rhyme or reason, but merely must be learned as particular structures in the brain -- the superior colliculus, the tegmentum, the globus pallidus, the substantia nigra, the cingulate cortex, and more. All of these structures come in pairs, with one in the left hemisphere and one in the right hemisphere; only the pineal gland is unpaired.
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Reference Manual on Scientific Evidence tions could be described, for example, as in the left anterior cingulate cortex, in the dorsal medial (or sometimes dorsomedial) prefrontal cortex, or in the posterior hypothalamus.
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At the same time, the fact that a region is necessary to a particular class of sensations, behaviors, or cognition does not mean either that it is not involved in other brain functions or that other brain regions do not also contribute to these particular abilities. The amygdala, for example, is involved in our feelings of fear, but it is also involved broadly in emotional reactions, both positive and negative.
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Unfortunately, the possibilities of this kind of extreme plasticity do diminish with age, but rehabilitation after stroke in adults sometimes does show changes in the brain functions undertaken by particular brain regions. The picture of the brain as a set of interconnected neurons that fire in networks or patterns in response to stimuli is useful but not complete.
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These methods, particularly the imaging methods that allow more precise measurements of human brain structure and function in living people, are giving rise to increasing efforts to introduce neuroscientific evidence in court. This section of this chapter focuses on several kinds of neuroimaging -- computerized axial tomography (CAT)
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CAT scan depicting axial sections of the human brain. The ventral most (bottom)
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was introduced into evidence to show that Hinckley suffered from organic brain damage in the form of shrinkage of his brain.4 2. PET scans and SPECT scans Traditional X-ray machines and their more sophisticated descendant, the CAT scan, project X rays through the skull and create images based on how much of the X rays are blocked or absorbed.
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PET scans are also very good for showing areas of different glucose use and, hence, of different levels of metabolism. This can be very useful, for example, in detecting some kinds of brain damage, such as the damage that occurs with Alzheimer's disease, where certain regions of the brain become abnormally inactive, or in brain regions that have been damaged by a stroke.
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PET has been substantially superseded for this purpose by functional MRI, which is less expensive, does not involve radiation exposure, provides better spatial resolution, and allows a longer period of testing. SPECT scans are similar to PET scans.
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This section discusses the general characteristics of MRI and then focuses on structural MRI, diffusion tensor imaging, and finally, functional MRI. The power of an MRI scanner is measured by the strength of its magnetic field, measured in units called tesla (T)
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to align with the direction of the main magnetic field of the magnet. Using a brief electromagnetic pulse, these aligned atoms are then "flipped" out of alignment from the main magnetic field, and, after the pulse stops, the nuclei then 767
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This ability makes structural MRI both an important clinical tool and a very useful technique for research that tries to correlate human differences, normal and abnormal, with differences in brain structure, as well as for research that seeks to understand brain development. Another structural imaging application of brain MRI has become increasingly prevalent over the past decade: diffusion tensor imaging (DTI)
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image of the human brain. Source: Courtesy of Anthony Wagner.
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This is the basis of the BOLD response, which measures changes in the ratio of oxyhemoglobin to deoxyhemoglobin in a brain region several seconds after activity in that region. In particular, when a brain region becomes more active, there is first, perhaps more intuitively, a decline in the ratio of oxyhemoglobin to deoxyhemoglobin immediately after activity in the region, apparently corresponding to the depletion of oxygen in the blood at the site of the activity.
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O'Craven & Nancy Kanwisher, Mental Imagery of Faces and Places Activates Corresponding Stimulus-Specific Brain Regions, 12 J
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Although fMRI research is subject to many questions and controversies (discussed infra Section IV) , this technique has been responsible for most of the recent interest in applying neuroscience to law, from criminal responsibility to lie detection.
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1. Lesion studies One powerful way to test whether particular brain regions are associated with particular mental processes is to study mental processes after those brain regions have been destroyed or damaged.
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Those brain regions were clearly involved in making new long-term memories for facts or events, but not in storing old ones.
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The precise manner by which DBS affects brain function remains unclear. Even for Parkinson's disease, for which it is widely used, individual patients sometimes benefit in unpredictable ways from placement of the lead in different locations and from different frequency or power of the stimulation.
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IV. Issues in Interpreting Study Results Lawyers trying to introduce neuroscience evidence will almost always be arguing that, when interpreted in the light of some preexisting research study, some kind of neuroscience-based test of the brain of a person in the case -- usually a party, though sometimes a witness -- is relevant to the case.
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A few of the brain regions are found to be important in most of the studies, but many of the other brain regions showing a correlation with deception differ from publication to publication. Only a few of the laboratories have published replications of their own work; some of those laboratories have actually published findings with different results from those in their earlier publications.
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, at 10, and in Anthony Wagner, Can Neuroscience Identify Lies? in A Judge's Guide to Neuroscience, supra note 1, at 30.
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C The Number and Diversity of Subjects Doing fMRI scans is expensive.
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It is highly unlikely than any fMRI pattern will be found always to occur under certain circumstances in every person tested, or even that it will always occur under those circumstances in any one person. Human brains and their responses are too complicated for that.
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. These variations can be more important with functional MRI (though they also apply to structural MRI)
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Neither way is "right" -- we do not know whether there is some minimum change in the BOLD response that means an "important" amount of brain activation has taken place, and if such a true value exists, it is likely to differ across brain regions, across tasks, and across experimental contexts. What this means is that different choices of statistical cutoff values can produce enormous differences in the apparent results.
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The techniques are fairly complex, and determining how to interpret the results of these tests can be controversial. Thus, these methods alone may require substantial and potentially confusing expert testimony in addition to all the other expert testimony about the underlying neuroscience evidence.
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V uestions About the Admissibility and Q the Creation of Neuroscience Evidence The admissibility of neuroscience evidence will depend on many issues, some of them arising from the rules of evidence, some from the U.S.
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The question, for example, would not be whether PET scans meet the evidentiary requirements to be admitted to demonstrate brain damage, but whether they have "any tendency to make the existence of any fact that is of consequence to the determination of the action more probable or less probable than it would be without the evidence."17 The brain damage may be relevant to a fact, but that fact must be "of consequence to the determination of the action." 2. Rule 702 and the admissibility of scientific evidence Neuroscience evidence will almost always be "scientific .
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We do not have the knowledge needed to analyze them in detail, but we will merely point out a few aspects that seem especially relevant to neuroscience evidence. Neuroscience evidence should often be subject to tests, as long as the point of the neuroscience evidence is kept in mind.
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Second, and more important, neuroscience evidence will almost never give an absolute answer, but will give a probabilistic one. For example, a certain brain structure or activation pattern will be found in some percentage of people with a particular mental condition or state.
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are particularly likely to overestimate the power of neuroscience evidence.21 20. Teneille Brown & Emily Murphy, Through a Scanner Darkly: Functional Neuroimaging as Evidence of a Criminal Defendant's Past Mental States, 62 Stan.
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4. Other potentially relevant evidentiary issues Neuroscience evidence will, of course, be subject in individual cases to all evidentiary rules, from the Federal Rules of Evidence or otherwise, and could be affected by many of them.
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(This does lead one to wonder whether a court would allow evidence from a psychic or from a fortune-telling toy, like the Magic Eight Ball, if both parties stipulated to it.) Second, polygraph evidence is sometimes allowed to impeach or to corroborate a witness's testimony.26 If a neuroscience-based lie detection technique were found to be as reliable as the polygraph, presumably those jurisdictions would have to consider whether to extend these exceptions to such neuroscience evidence.
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141 (2008) ; William Federspiel, Neuroscience Evidence, Legal Culture, and Criminal Procedure, 16 Wm.
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c. Other substantive rights against neuroscience evidence At least one form of possible neuroscience evidence may already be covered by statutory provisions limiting its creation and use -- lie detection.
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Most of these seem clearly aimed at polygraphy, but, in some states, the language used is quite broad and may well encompass neuroscience-based lie detection.37 States also may provide protection against neuroscience evidence that goes beyond lie detection and could prevent involuntary neuroscience procedures. Some states have constitutional or statutory rights of privacy that could be read to include a broad freedom for mental privacy.
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d. Neuroscience evidence and the Sixth and Seventh Amendment rights to trial by jury One might also argue that some kinds of neuroscience evidence could be excluded from evidence as a result of the federal constitutional rights to trial by jury in criminal and most civil cases.
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It seems likely that neuroscience evidence will first be offered by parties who have been its voluntary subjects and who will argue that it strengthens their cases. In fact, the main use of neuroimaging in the courts so far, at least in criminal cases, has been by defendants seeking to demonstrate through the scans some element of a defense or mitigation.
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There are very few cases, civil or criminal, where the mental states of the parties are not at least theoretically relevant on issues of competency, intent, motive, recklessness, negligence, good or bad faith, or others. And even if the parties' own mental states were not relevant, the mental states of witnesses almost always will be potentially relevant -- are they telling the truth?
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Two amicus briefs argued that behavioral and neuroscience evidence supported this position. See Brief of Amicus Curiae American Medical Association et al., Roper v.
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at 1063–67. Judge Kennelly's discussion of this point may be a good example of the kind of analysis neuroscience evidence may force upon judges.
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Many, but not all, of these issues have begun to be discussed in the literature. A few of them, such as criminal responsibility, mitigation, memory detection, and lie detection, are appearing in courtrooms; others, such as pain detection, have reached the edge of trial.
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The defendant was sentenced to death, but after longer jury deliberations than defense counsel expected.51 (This appears to have been the first time fMRI results were introduced in a criminal case.52) Neuroscience evidence also may be relevant in wider arguments about criminal justice.
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Similarly, most of the neuroscience evidence will be from associations, not from experiments. It is hard to imagine an ethical experiment that would scan people when they are, or are not, committing particular crimes, leaving only indirect experiments.
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Stoller & Paul R Wolpe, supra note 27; Mark Pettit, FMRI and BF Meet FRE: Braining Imaging and the Federal Rules of Evidence, 33 Am.
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Wagner, supra note 12; and S.E. Christ et al., The Contributions of Prefrontal Cortex and Executive Control to Deception: Evidence from Activation Likelihood Estimate Meta-Analyses, 19 Cerebral Cortex 2557 (2009)
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As a class of experiments, these studies are subject to all the general problems discussed in Section IV regarding fMRI scans that might lead to neuroscience evidence. So far there are only a few studies involving a limited number of subjects.
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. 67. See supra note 59.
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The judge decided the lie detection evidence was not appropriate under New York's version of the Frye test, noting that, in New York, "courts have advised that the threshold question under Frye in passing on the admissibility 68. Wilson v. Corestaff Services, L.P., supra note 60.
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. 70. See Wilson, supra note 60, at 7.
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The brain regions identified as part of the so-called pain matrix vary from researcher to researcher, but generally include the thalamus, the insula, parts of the anterior cingulate cortex, and parts of the cerebellum.73 Researchers have run experiments with subjects in the scanner receiving painful or not painful stimuli and have attempted to find activation patterns that appear when pain is perceived and that do not appear when pain is absent. (The subjects usually are given nonharmful painful stimuli such as having their skin touched with a hot metal rod or coated with a pepper-derived substance that causes a burning sensation.)
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They show activation in the pain matrix. In some fMRI studies, people who have been hypnotized to feel pain, even when there is no painful stimulus, show activation in the pain matrix.77 And in one fMRI study, subjects who reported feeling emotional distress, as a result of apparently being excluded from a "game" being played among research subjects, also showed, on average, statistically significant activation of the pain matrix.78 Pain also plays an enormous role in the legal system.79 The existence and extent of pain is a matter for trial in hundreds of thousands of injury cases each year.
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Does remembered pain look the same in an fMRI scan as currently experienced 80. Adam J Kolber, How to Improve Empirical Dessert, 75 Brook.
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Who would pay for these scans and for the experts to interpret them? Detecting pain would be a form of neuroscience evidence with straight forward and far-reaching applications to the legal system.
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Reference Manual on Scientific Evidence References on Neuroscience Fundamental Neuroscience (Larry R Squire et al.
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