Guilty of a Broken Brain

Neuroscience is finding itself at the center of a growing controversy in the courtroom. Will judges weigh biological evidence that could suggest future dangerous activity or impaired control differently and how will that affect systems of sentencing and determinations of guilt in the court? This biological evidence could be considered “mitigating” or decreasing a sentence (their brain is broken, it’s not their fault) or it could be “aggravating” (their brain is broken and they will offend again) and increase a sentence. To test whether Judges would reason differently after receiving biological evidence in a trial, a group has conducted a study on U.S. state trial judges.

Judges were presented with a mock case (based loosely on an actual case Mobley v. State), in which a man beat a restaurant manager until he had permanent brain damage when he refused to turn over money from the register.  The judges were randomly assigned to four conditions: 2 presenting parties (prosecution or defense) and 2 biomechanism groups (absent or present). They were presented identical testimony from a psychiatrist diagnosing the man as a psychopath. Judges in the biomechanism present group heard testimony from a neurobiologist stating that the man had a genetic variation and atypical brain function which predisposed him to violent behavior. In the prosecution condition, prosecutors argued that this evidence should be considered aggravating because he likely posed a continued threat to society. In the defense condition, it was argued that the evidence be considered mitigating because the defendant had a more difficult time controlling his impulses due to his genetic abnormalities. These conditions should allow the researchers to understand how biomechanistic evidence affects judge’s reasoning in sentencing.

The data they gathered from the study is certainly suggestive but I think statistically it leaves a little to be desired. The judges who were presented with the neurobiologist’s testimony tended to give a slightly lesser sentence to the offender, 13 years as opposed to the Judges who did not receive the neurobiologist’s testimony who sentenced the offender to 14 years. However, these judges were compiled from many U.S. states whose sentencing guidelines can vary significantly (this is obvious with a large standard error of the mean for the sentencing data). I think more telling is the data showing that biomechanistic data significantly reduced the judges rulings on aggravation. This suggests that many of the judges find evidence of biological dysfunction to decrease the culpability of a defendant because their behavior is less in their control.

This study raises several issues about the place of neuroscience in the courtroom. Should genetic variations and developmental abnormalities lessen the punishment for criminals? These people have still broken the law regardless of the underlying cause. How can we separate the brain from the person? Are we simply a sum of our genetic code not to be held responsible for learning social mores and obeying laws?

Commentary on the study

Further Reading

One thought on “Guilty of a Broken Brain”

  1. Seems to me like a measure using deviations from average/recommended sentence would have been a better metric than the absolute number of years sentenced. Which, of course, has little to do with the overarching theoretical issues.

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