This will be my last post as a guest blogger. Thanks so much to Adam for inviting me to contribute. Much of the argument below was adapted from a chapter I wrote for this forthcoming OUP volume edited by Nicole Vincent.
There are legitimate worries about gaps between the concepts normal people (the “folk”) use to attribute criminal responsibility and neuroscientific data. For example, evidence of a brain tumor may, or may not, be relevant to a criminal trial. Did the defendant have the tumor at the time the crime was committed? Is the tumor in a place relevant to the formation of his intention to cause criminal harm? Can a jury reliably infer, say, that a tumor lessened an ability to inhibit action, and from there to an assumption that the defendant couldn’t have formed the intention to kill in a normal way?
Despite these worries, attorneys in the criminal courts are using neuroscientific evidence at an ever-increasing rate. Expert witnesses called by both prosecution and defense debate the questions above, leaving judges and juries to determine whether or not to take neuroscience into consideration in their assessments of guilt and punishment.
I think this is just as it should be. With the introduction of any new technology or scientific concept (e.g. fingerprint evidence, DNA evidence, or evidence of a newly discovered or popularized mental disorder) there is always an adjustment period during which the courts try to figure out its utility and relevance. Progress is made largely via trial and error, although scholarly work sometimes plays a role. Slowly the reliability of the new type of evidence becomes more clear. There is no deep worry that this process will generate an unjust result, slow and uneven as it may be, unless there is some principled argument as to why neuroscientific evidence is irrelevant to criminal verdicts.
But presently no such argument exists. The two arguments made most often both fail. The first states that folk psychology does such a good job of attributing the mental states necessary for criminal responsibility using behavioral evidence that neuroscientific evidence is unnecessary—it provides no added value, just added headaches. (Stephen Morse has made this type of argument.) If judges and juries are currently correct in their attributions of criminal responsibility to defendants, the system does not need to be supplemented with neuroscience.
This argument fails to recognize the shortcomings of the commonsense system of attributing mental states and capacity to defendants. Folk psychology operates through something close to cognitive heuristics, whereby mental states are attributed based on theoretical assumptions regarding human behavior and outward behavioral cues. Thus, as trial attorneys know well, it can be manipulated. When I was working at the juvenile courthouse in Chicago, I heard stories of prosecutors not allowing juvenile offenders to shave, and giving them clothes a size too small, in an attempt to make their request to transfer the juvenile to adult court more convincing. At the adult courthouse, defense attorneys told me of a catch-22 with their mentally retarded defendants: if they testify, they are more likely than normal defendants to admit to something terrible (and untrue) on cross-examination, but if they don’t testify, the jury often claims that they look “perfectly capable” sitting at the defense table.
Criminal verdicts based on folk psychology are subject to a variety of arguably unreliable influences and behavioral data that push and pull commonsense mental state attributions in different directions. Although it is true that neuroscientific evidence can also be manipulated to interact with folk concepts in unprincipled and unhelpful ways, such evidence may be more reliable than behavioral evidence if presented using a good theory of how the science speaks to legal criteria. For example, neuroscience might be used to help refute a presumption that a juvenile (who looks older and committed a particularly heinous crime) is fully cognitively mature.
A second argument in support of the claim that neuroscience should be kept out of the courts is that the gap between the folk concepts used to attribute responsibility and neuroscientific evidence is on principle insuperable. Some scholars have claimed that it is unlikely we will be able to reduce folk concepts to neuroscientific concepts, or vice versa. Some versions of nonreductivism indicate that direct evidence of brain function or disorders should not be considered by courts seeking to judge criminal responsibility because the way they map onto mental states is “fundamentally mysterious.”
I have argued that there is no reason to believe that there is a necessary gap between folk concepts and scientific evidence of brain states because there is no evidence that folk concepts fail to refer to real entities in the brain. Further, the nonreductive position regarding the relationship between the mind and brain fails as applied to the criminal law in one of two ways. If there is really such a loose connection between the mind and brain so that it remains “fundamentally mysterious,” nonreductivism fails to preserve mental causation, an idea the criminal law relies upon. The criminal law demands that a defendant’s desire to kill caused the bodily act that resulted in an unlawful death. Any theory that failed to preserve this connection would undermine our entire system of attributing responsibility.
If, however, a theory of nonreductive physicalism does preserve mental causation, it strengthens the relationship between the mind and brain to the point that mental states and brain states can at minimum be causally identified. In this case the modest claim that neuroscience may be relevant to mental state attributions couched in folk terms isn’t threatened by non-reductivism.
Thus while neuroscience might be predjudical or even misleading in certain cases, we may hope that over time its use by the criminal courts will result in more accurate and just verdicts.