Science has attained a high degree of credibility in Western societies. Society appeals to science to settle all kinds of dilemmas—including moral ones—that confront human beings. Issues of punishment, especially the death penalty, are some of the biggest moral dilemmas confronting society. What used to be the domain of philosophers and social scientists using moral and statistical arguments has been largely co-opted by geneticists and neuroscientists. According to some, this co-optation has challenged the foundations upon which the legal system rests—the assumption that individual agency underlies the capacity to make moral choices. It is also argued that the “hard” scientific evidence accepted uncritically by the courts for mitigation purposes will weaken traditional ideas of justice by undermining human responsibility.
A number of brain imaging techniques are used in neuroscience research and in clinical situations, but the one used most frequently in court proceeding in support of mitigation is functional magnetic resonance imaging (fMRI). FMRI allows insight into the functioning of the brain in real time. These scans use a large cylinder-shaped tube, which produces powerful magnetic fields and radio frequency pulses, all of which are connected to computers that generate colored pictures of a person’s brain in action. Subjects in the fMRI tube respond to questions by pressing buttons on a response box. As the person performs these tasks or emotionally responds to the stimuli, a computer picks up and stores information about the regions of the brain being used. Like the muscles of the body, the harder the brain works the more oxygen it requires, so when a particular region is activated, more blood containing oxygen is routed to that region. The basic fMRI procedure uses what is known as the blood-oxygen-level-dependent (BOLD) contrast.
Data from fMRI testing are based on aggregating the BOLD responses (the contrast between the magnetic resonance of oxygenated to deoxygenated blood) of a number of individuals. FMRI results emerge from data averaged over a group of subjects and are thus problematic when applied to specific individuals. Defense attorneys typically use fMRI data to mitigate responsibility, but because a particular pattern of neural activity is associated with some impairment of judgment on average it does not necessarily mean that the defendant has the same impairment even if his brain shows roughly the same pattern.
There are many issues with the use of fMRIs in court. Neuroimaging evidence relating to which parts of the brain are activated under what conditions, and what parts are associated with what behaviors, is both consistent and strong. However, neuroimages are maps of the terrain, not the terrain itself. The color images of the brain produced are not direct images like X-rays; they are pictures generated by mathematical algorithms. They are indirect rather than direct evidence of increased neural activity derived from data based on a statistical aggregate that form a correlation between a particular trait or behavior and BOLD responses in a particular brain area. A correlation is a trend in a given direction, and that correlational trend is not true of all brains tested, and certainly not in terms of the wide variations in strength of brain responses of different people to identical stimuli. FMRI data are very useful, but the data are still statistical, and statistical data are probabilistic by definition.
It is a big jump from talking about “impaired judgment” inferred from errors noncriminal subjects make on tasks they perform in the laboratory and a brutal murder performed in the real world. Just how impaired is the defendant’s brain relative to the average level of impairment found in research subjects, and how many of these subjects similarly impaired have committed murder? For instance, in Roper v. Simmons, U.S. Supreme Court Justice Anthony Kennedy cited a blizzard of scientific evidence on the immaturity of the juvenile brain in support of the court’s ruling that the death penalty for juveniles was unconstitutional. Opponents of the use of fMRI data for purposes of mitigation (regardless of their stance on the death penalty) would ask if Christopher Simmons’s brain is any more or any less immature than millions of other adolescents who did not plan, execute, and brag about a horrendous murder.
Another matter is that defendants’ brains are typically imaged long after—often years after— the crime was committed. Today’s brain is not yesterday’s brain, and the images judges and jurors may see in court may be vastly different from what they may have seen shortly after the crime for which the defendant is seeking mitigation. A scan of a serial killer’s brain, for example, may unequivocally show that he is a psychopath, but it reveals nothing about his state of mind when he committed his brutal acts, nor in any way does it show that he was incapable of controlling his behavior. Brain scans have tremendous importance in medicine and neuroscience research, but they cannot read minds, particularly mind states that occurred years prior to scanning. Scanning records the probable state of the subject’s mind at the time of the scan; it cannot settle matters of legal responsibility. Thus, the principal concern regarding brain scans in court is that the aura of “hard” science and the impressive colorized maps of brains they produce will unduly undermine the traditional legal concerns of responsibility.
- Jones, Owen, Joshua Buckholtz, Jeffrey Schall, and Rene Marois. “Brain Imagining for Legal Thinkers: A Guide for the Perplexed.” Stanford Law Review, v.5 (2009).
- Logothetis, N. and J. Pfeuffer. “On the Nature of BOLD fMRI Contrast Mechanism.” Magnetic Resonance Imaging, v.22 (2004).
- Morse, Stephen. “Brain Overclaim Syndrome and Criminal Responsibility: A Diagnostic Note.” Ohio State Journal of Criminal Law, v.3 (2006).