Neuroscience and the Law: Brain, Mind, and the Scales of Justice

This volume is a report of a workshop sponsored by the American Association for the Advancement of Science and the Dana Foundation, which supports brain research. Part 1 distills the deliberations, and part 2 presents commissioned papers—two by neuroscientists and two by legal scholars.

The theme is the implications of neuroscientific developments for the legal system. The normative implications vary from important to minimal for law and society. The topics vary, including prediction of behavior, neuropsychiatric instruments that can be used for help in competency determinations, improvement in lie detection, informed consent, and brain death. Enhancing performance raises the possibility of mandated enhancement, such as requiring people to take an antidepressant drug to make them less angry, irritable, or impulsive. The paper by Dr. Tancredi raises many possibilities that may occur in the future and almost sound like science fiction, but they are not. Transcranial magnetic stimulation can create temporary “strokes” by inhibiting an area or, conversely, boost functioning temporarily in an area. Some of the procedures have potential for brain modification as part of treating addictions when addicted brains are different.

The potential for discrimination based on neuroscientific tests and procedures raises issues regarding “exceptionalism.” Questions of privacy and confidentiality are troublesome, such as the extensive information gathered in a single imaging procedure. Four questions are posed for the use of neuroscience in litigation: 1) Does the information meet legal admissibility standards (Frye[1] and Daubert[2] standards)? 2) If admissible, are there other reasons that should preclude courts from using the information? (Should a court allow testimony that a person has a superior memory? Those opposed argue this invades the province of the jury, and those in favor argue it is similar to testimony about a person’s vision.) 3) Should the willingness or refusal to take neuroscientific tests be introduced? 4) Should a witness, or any person involved in the litigation process, be compelled to be tested and, if so, under what circumstances?

A recurrent question involves determinism and neuroscientific findings. If people’s actions are caused by factors for which they are not responsible, how can they be held responsible for actions that occur as a result of these factors? This old issue obviously has implications for the legal system. To be responsible presumably means at the minimum that we are responsible for at least the majority (51%?) of what has caused the actions. Yet, experiments show that before a person is even consciously aware of a decision to perform an act, the brain was active with a “readiness potential.” The brain, as a physical organ, is thus carrying on its work before conscious awareness, as an enabler for the mind. Similarly, positron emission tomography (PET) shows that individuals with antisocial personality disorders with impulsive aggression do not activate the anterior cingulate in response to a serotonergic stimulus (m-chlorophenylpiperazine) normally involved in inhibition. Yet, questions remain, such as whether the person simply chose not to inhibit the action.

Can there be free choice in a deterministic scientific world of explanation? When a violent act occurs, the quest is not simply to understand it as a pixel on a brain scan but to assess responsibility. However, the legal rules focus on not thinking clearly to the point that the ability to inhibit acts is impaired. Responsibility is a social construct and does not exist in the neuronal structure of the brain. Of course, social rules are not based on neuroscientific findings, but the findings raise issues for the legal system that cannot be ignored.

Professor Morse, while rightfully regarding these questions as “old problems” for the legal system, cites studies of biological cases that predispose people to behave in certain ways. Thus, maltreated children were likely to exhibit later antisocial behavior if they had an impairment in the enzyme monoamine oxidase A, which metabolizes neurotransmitters linked to violence. Although assessing responsibility is done by legal rules, should the rules take account of such scientific research in finding the person responsible or simply ignore the research?

Discussion of these issues leaves the impression of three disparate approaches with their own preconceptions and goals. First is the unresolved philosophical debates about “free will” in terms of determinism or its lack. These use a framework of compatibilism or incompatibilism regarding determinism and freedom. Second, the neuroscientific approach uses increasingly sophisticated technology that raises questions about the functioning of the brain and its mysterious relationship to the mind. Third, the legal system assesses responsibility of people as intentional agents governed by reason. Morse does not see neuroscientific work as having many normative implications for law, as many believe. This is because he does not see responsibility having anything to do with “free will” but, rather, the capacity for rationality. He does not ignore the increase in biological knowledge, but he does not believe it negates a view of humans as causally efficacious. As he puts it, “If the realism constraint is true, all behavior is caused, but not all behavior is excused, because causation per se has nothing to do with responsibility. If causation negated responsibility, no one would be morally responsible, and holding people legally responsible would be extremely problematic” (p. 177). However, that is the problem, not a solution.

Have the workshop and the discussants resolved the problems of responsibility and new neuroscientific findings? Clearly not, but they have given a stimulating discussion of continuing issues.