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Psychopathy and Mitigation

As detailed by Kelly Lowenberg over at the Stanford Law and Neuroscience Blog, psychopathy was recently introduced as a mitigating factor in a capital murder trial:

[N]euroscientist Kent Kiehl recently testified as an expert witness for the defense in the sentencing hearing for Brian Dugan, a man who pled guilty to the 1983 rape and murder of a ten-year old girl. The defense argued that Dugan suffers from psychopathy, a psychiatric disorder typified by antisocial behavior, impulsivity, and lack of remorse, which made it difficult for him to control his behavior. As a result, the defense argued, Dugan is less culpable for his criminal behavior, and his disorder should be considered a mitigating factor. Kiehl testified that based on functional magnetic resonance imaging (fMRI) tests and a diagnostic checklist, Dugan showed abnormal brain functioning and responses similar to other psychopaths Kiehl has tested.
But the crucial question is what is that abnormal brain functioning?  Is it an abnormality that renders the defendant unable to bring reason to bear on his or her decisions?  Keep in mind that the hallmark feature of psychopathy is willful engagement in planned, predatory behavior.  Neurotalk can make any behavior sound pathological, but describing brain patterns doesn't equate to excuse (yet) in any jurisdiction.

But what if those doctrines were to change?

At the least, they were have to hold that defendants who have a sophisticated enough understanding of legal wrongfulness that they often engage in planned behavior designed to subvert detection by law enforcement are insane.  What's more, they would hold that citizens who have antisocial tendencies, are impulsive, and hurt other without feeling bad about it deserve excuse. 

And that is no small doctrinal change.


In the sentencing phase of a capital trial, the factor the defendant claims in mitigation doesn't need to be a legal excuse. The Lockett rule allows him to throw anything he wants against the wall and hope it sticks with at least one juror.

In 1993, Justice Thomas used exactly the example described here to illustrate how absurd the Lockett rule had become.

Every month, defendants who claim a special victimization file with this Court petitions for certiorari that ask us to declare that some new class of evidence has mitigating relevance "beyond the scope" of the State's sentencing criteria. It may be evidence of voluntary intoxication or of drug use. Or even - astonishingly - evidence that the defendant suffers from chronic "antisocial personality disorder" - that is, that he is a sociopath. See Pet. for Cert. in Demouchette v. Collins, O. T. 1992, No. 92-5914, p. 4, cert. denied, 505 U. S. 1246 (1992). We cannot carry on such a business, which makes a mockery of the concerns about racial discrimination that inspired our decision in Furman.

Graham v. Collins, 506 U.S. 461, 500 (concurrence).

Of course Kent is right insofar as this is a sentencing case. But the door has been opened (and his hard to shut once it is opened).

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