Crime and biology


Jason Collins


June 22, 2011

The July/August 2011 edition of the Atlantic has a great article by David Eagleman on the implications of advances in brain science on the way we approach crime (HT: Jeffrey Horn). Eagleman argues that these advances will require a reshaping of the criminal justice system to reflect the declining gap between whether actions can be attributed to biology and free will. Eagleman writes:

Technology will continue to improve, and as we grow better at measuring problems in the brain, the fault line will drift into the territory of people we currently hold fully accountable for their crimes. Problems that are now opaque will open up to examination by new techniques, and we may someday find that many types of bad behavior have a basic biological explanation—as has happened with schizophrenia, epilepsy, depression, and mania.


The crux of the problem is that it no longer makes sense to ask, “To what extent was it his biology, and to what extent was it him?,” because we now understand that there is no meaningful distinction between a person’s biology and his decision-making. They are inseparable.

Eagleman’s first response to this problem is to move away from blameworthiness. If you cannot distinguish the extent of volition (if it can even be argued to exist), it is hard to blame. As a result, Eagleman suggests that justice will need to become more forward-looking:

Instead of debating culpability, we should focus on what to do, moving forward, with an accused lawbreaker. I suggest that the legal system has to become forward-looking, primarily because it can no longer hope to do otherwise. As science complicates the question of culpability, our legal and social policy will need to shift toward a different set of questions: How is a person likely to behave in the future? Are criminal actions likely to be repeated? Can this person be helped toward pro-social behavior? How can incentives be realistically structured to deter crime?

Deeper biological insight into behavior will foster a better understanding of recidivism—and this offers a basis for empirically based sentencing. Some people will need to be taken off the streets for a longer time (even a lifetime), because their likelihood of reoffense is high; others, because of differences in neural constitution, are less likely to recidivate, and so can be released sooner.

While I agree the criminal justice system should ask what the law-breaker is likely to do in the future, it cannot desert the look in the rearview mirror. If you wish the justice system to offer an incentive to not commit crimes, it needs to act retrospectively or the threat of punishment will not be credible. If people have a biological propensity to commit a crime, you may need to make these incentives even stronger (Steven Pinker discusses this argument in The Blank Slate.

To make his forward-looking approach work, Eagleman suggests that the courts use statistically based sentencing. Statistical analysis can be used to find out which factors have the highest link to re-offending - and the evidence suggests that this is more accurate than leaving it to judges. I suggested this recently in response to the finding that the timing of lunch breaks in Israeli courts. Human judgement is a primary weakness in the criminal justice system. However, there will need to be a component of the algorithm that provides a certain, strong punishment that potential criminals can take into account.

While Eagleman’s article is thorough, there is one biological element missing from his analysis - the dynamic effects. Incarceration removes young men from the mating market during their mating prime. As the propensity to commit crime is heritable, the removal of criminals from the mating market will reduce the frequency of the genes associated with crime in the next generation. As Eagleman notes:

[I]f you are a carrier of a particular set of genes, the probability that you will commit a violent crime is four times as high as it would be if you lacked those genes. You’re three times as likely to commit robbery, five times as likely to commit aggravated assault, eight times as likely to be arrested for murder, and 13 times as likely to be arrested for a sexual offense. The overwhelming majority of prisoners carry these genes; 98.1 percent of death-row inmates do.

Instead of worrying about how to control the biologically impulsive, incarceration can simply cut their prevalence in the future.