Exploring the Final Frontier—The Relevance of Brain Imaging in Litigation

Mary Riverso, MJLST Staffer

Human curiosity and technological advancements have led to the exploration of the ends of the earth, the deep seas, even outer space. We have learned so much about the animals we live amongst, the nooks and crannies of planet Earth, and our role in the universe. But as we continue to explore farther and farther outward, we often overlook how little we actually know about ourselves.

The human brain remains predominantly mysterious and unknown. Neuroscientists continue to attempt to map the brain, to assign different functions and behaviors to the different regions of the brain supposedly responsible for them. However, a thorough understanding remains nearly impossible given the intricate circuitry of brain functioning. While certain areas of the brain are sometimes responsible for discrete tasks, complex functions are not exclusively localized. It is more accurate to think of the brain as composed of neuron circuits – the different regions constantly connecting with one another via neuron circuits to work together to process information and complete tasks. Technological advancements now allow for many groundbreaking and non-invasive means of observing the functioning brain. For example, devices administering scans for functional magnetic resonance imaging, or fMRI, monitor blood flow to detect areas of activity. Whereas an electroencephalogram, or EEG, is a test that measures and records the electrical activity of your brain. Finally, magnetoencephalography, or MEG, captures the magnetic fields generated by neural activity. As the capacity and means to monitor brain functioning expand, the potential for successful brain mapping increases. As a result, using brain images resulting from these scans as evidence in litigation becomes more tempting.

The potential for brain imaging to be used as expert evidence in litigation is already being explored. Criminal defendants, such as Herbert Weinstein, want to use the results from brain scans and tests to show that they are not responsible for their criminal actions due to a physical mental disease or defect. Other defense teams see the potential of brain imaging to aid in assessments of truth-telling. Physicians who administer the tests must be willing to testify as expert witnesses to the results and their medical conclusions. Often times, the physicians probe brain function and analyze energy utilization of the brain and then administer tests of human behavior and mental representations to provide a basis for their medical conclusions. However, a major hurdle for potential neuroscientific evidence is its relevance under Federal Rule of Evidence 401 (“FRE 401”). FRE 401 demands that before such evidence be admitted, it must have a tendency to make a fact of consequence more of less probable. But because the brain remains so misunderstand, it is difficult, or arguably impossible, to draw any exact conclusions that a physical disease or defect in fact caused a behavioral or mental defect.  As a result, courts have come out on either side of the threshold issue in FRE 401 – some have found that the neuroscientific evidence is appropriate for consideration by a jury who can decide what inferences to draw from it, while others find that this kind of evidence is too prejudicial while being only minimally probative and exclude the evidence under FRE 403, and still others allow the evidence but only for limited purposes, such as the sentencing phase of proceedings instead of the guilt phase. As technology continues to advance and neuroscientists continue to learn more about brain functioning, this kind of evidence may become commonplace in litigation. But for now, the admissibility decision seems to be fact-and-circumstance dependent, based on the case, the expert, the evidence, and the judge.