cell | Advances in understanding genetic predispositions to
behavioral and neuropsychiatric syndromes are squarely in the sights of
the legal profession. With data suggesting substantial genetic
contributions to the risk for criminal behavior (Tuvblad et al., 2011), attorneys have begun to explore the potential uses of genetic evidence in their clients’ defense (Denno, 2011).
In addition, the first signs that genetic data may be of interest to
the civil justice system have begun to appear. As is true whenever
scientific data are introduced in court, these developments hold
potential for assisting judges and juries with some of the difficult
judgments that they face—but they also bring a substantial risk of
misinterpretation and misuse.
In considering current and
future uses of behavioral and neuropsychiatric genetic evidence, the
unhappy history of genetics in the courtroom cannot be ignored. Even
before the structure of DNA was identified and the transmission of
genetic information elucidated, courts recognized that behavioral traits
could be handed down in families. However, judges’ understanding of
genetics typically reflected the science of the day, and the
consequences of their reliance on contemporary knowledge were not always
salutary. For example, in the U.S. Supreme Court’s decision in Buck v. Bell
(274 U.S. 200, 1927), which upheld Virginia’s involuntary sterilization
statute, Justice Oliver Wendell Holmes, appealing to the popular view
that intellectual disability was passed from parent to child and was
associated with promiscuity and crime, notoriously declared, “It is
better for all the world, if instead of waiting to execute degenerate
offspring for crime, or to let them starve for their imbecility, society
can prevent those who are manifestly unfit from continuing their kind.”
Presumptions
about the relationship between crime and hereditary intellectual
deficiencies appear to have influenced the lower courts as well, with
defendants who were viewed as “defective delinquents” often sent to
state institutions where they could be confined indefinitely, rather
than being sentenced to a fixed term in a correctional facility (Willrich, 1998).
But the first use of genetic tests in the courts for their presumed
relationship to criminal behavior did not arrive until the late 1960s
and was based on data purporting to show that the XYY karyotype was
linked to violent crime (Denno, 1996).
Derived from a number of studies demonstrating overrepresentation of
XYY men in correctional populations, the data were recruited by
enterprising defense attorneys to argue that their clients’ violence was
driven by genetic factors beyond their control, and thus that they
could not be held criminally responsible for their behavior. Courts,
however, were skeptical about the validity of data suggesting a causal
link between the XYY karyotype and violent behavior and generally
declined to admit karyotyping of defendants into evidence. As it turned
out, the courts’ skepticism was fully justified—the purported link
between XYY and violence has never been generally accepted (Stochholm et al., 2012).
