MadSci Network: Neuroscience |
I think first of all this question is more of a philosophical question, rather than a scientific question. You have not asked whether genes influence our risk for committing violence (which would be a scientific question), but rather if we still responsible for violent acts when they do (a philosophical/legal question).
I am not an attorney but my understanding of the law is that we are responsible for a criminal act as long as we understand the distinction between right and wrong. The insanity defense rests on this notion. To date, no cases (see the very good article below) have successfully used a defense that "my genes made me do it" because, while genes may increase our risk of being violent (like the MAO genes described below), we are still considered to have free will in the eyes of the law.
Human behavior is very complicated, and can not be reduced simply to genes; it is a product of an interaction between the environment and genetics. If one can show that a gene predisposes towards violence, and one had a life that included substantial abuse as a child, I could see this as mitigating circumstances which might affect the sentencing, but you would have to argue that this combination of environment and genetics did not allow you to distinguish right from wrong, which is an unlikely event.
I do believe that individuals with severe mental disease such as schizophrenia
are not able to tell right from wrong when they are in the midst of a
psychotic episode, but even then the legal system is very hesitant to go along
with an insanity defense.
hope this helps
Gabriel Vargas. MD/PhD
Reference: Paul S. Appelbaum, M.D. (2005) Law & Psychiatry: Behavioral Genetics and the Punishment of Crime Psychiatr Serv 56:25-27.
Law & Psychiatry: Behavioral Genetics and the Punishment of Crime
Paul S. Appelbaum, M.D.
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Behavioral genetics would seem to have little impact on the daily work of
most mental health professionals, attorneys, judges, and others involved in
the criminal justice system. Arcane research findings, often not
replicated, that suggest some link between genes and the propensity to
commit criminal acts are currently of dubious relevance to a system that
struggles simply to provide basic justice to a complex mix of criminal
defendants. Recent research findings, however, suggest that behavioral
genetics may be the next frontier for the world of criminal justice, and
mental health professionals are likely to play a critical role in helping
the courts make sense of the new data.
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Of course, claims that hereditary factors play a causal role in the genesis
of criminal behavior are hardly new. Late 19th- and early 20th-century
theories of crime relied heavily on now-discredited beliefs that offenders
who manifested hereditary degeneration, which was believed to be apparent
by their physiognomy and low intelligence, were responsible for a majority
of criminal acts (1). In the 1960s and 1970s men who carried an extra Y
chromosome—the so-called XYY syndrome—were thought to be at increased risk
of violence, another subsequently disproven contention (2). The latest
findings on a connection between genetic predispositions and violent crime,
however, are much more sophisticated and are already stirring considerable
interest in the legal literature.
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A 1993 report in the respected journal Science described a Dutch kindred in
which several males exhibited a syndrome of borderline mental retardation
and "abnormal behavior, including disturbed regulation of impulsive
aggression" (3). They were found to have a complete absence of activity of
the enzyme monoamine oxidase A (MAOA), which breaks down many of the
brain's key neurotransmitters. Genetic analysis revealed that the affected
men carried a mutation on the X chromosome in the gene that codes for MAOA.
As intriguing as this finding was, it seemed to be of limited import for a
general understanding of genetic factors affecting violence, because
complete absence of MAOA activity was clearly rare.
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Just under a decade later, however, Science published another paper that
extended the scope of the MAOA findings. This time the data came from a
major longitudinal study of a birth cohort of 1,037 children in Dunedin,
New Zealand. The participants had first been assessed at three years of age
and had just completed their ninth follow-up at the age of 26 years (4).
Because mutations that lead to an absence of MAOA activity were unlikely to
be present, the researchers examined 442 males in the group for differences
in the promoter region of the gene, which determines how strongly the gene
is expressed (that is, how much MAOA is produced). And rather than merely
looking at the effect of MAOA levels on criminal behavior, the
investigators explored the interactions of the participants' genetic
endowments with their environmental circumstances. Specifically, the
researchers were interested in how experiences of maltreatment between the
ages of three and 11 years affected the later antisocial propensities of
participants with either a high or low MAOA activity.
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Using four separate measures of antisocial behavior, including convictions
for violent crime, the research team found that each measure was
significantly increased in the group that had both low MAOA activity and a
history of severe maltreatment. In contrast, for participants with high
levels of MAOA, no significant increase was found in any of the antisocial
measures, even when they had experienced the same level of maltreatment.
The overall impact of this gene-environment interaction can be judged from
the fact that the 12 percent of the cohort that had both low MAOA and
maltreatment accounted for 44 percent of the cohort's convictions for
violent crime. Looked at somewhat differently, 85 percent of the males with
both risk factors developed some form of antisocial behavior.
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It did not take long for the Dunedin data to be noticed by the legal
community and for the potential impact of these findings on the criminal
process to become the object of intense speculation (5,6). The elegance of
the Dunedin data notwithstanding, it is worth underscoring that the results
will, as the authors themselves noted, require replication before being
accepted as established fact. However, whether or not the Dunedin findings
stand up to scrutiny, it seems likely that with continued advances in
behavioral genetics we will at some point be able to identify genes that
combine with environmental stimuli to predispose persons to increased rates
of criminality, including violence.
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One important question for the criminal justice system, therefore, concerns
the applicability of the MAOA data and similar findings for determining
criminal responsibility. Anglo-American law has created categories that
excuse defendants from culpability when their capacity to choose their
behaviors is significantly impaired. The insanity defense and the defense
of automatism are two well-known examples. If mental disorders that impair
the understanding or appreciation of wrongfulness or the ability to control
behavior negate culpability, why should genetic determinants (for example,
low MAOA activity) with similar consequences not have the same effect?
Indeed, one author has already proposed a defense of "genetic determinism"
that would work in this way (7).
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This would not be the first time that courts have had to grapple with such
claims. In the 1970s several defendants attempted to introduce evidence of
their XYY status in an effort to negate their culpability. Courts uniformly
rejected the defense, but the grounds for their decisions varied. Their
rulings were based alternatively on the conclusions that only a showing of
legal insanity would excuse the defendant, that XYY syndrome did not
constitute a requisite "mental disease or defect," that evidence
demonstrating a causal link between XYY and violence was not sufficiently
certain to be admitted, and that even if XYY predisposed a defendant to
violence, it was not possible to show that any particular behavior was
linked conclusively to the genetic abnormality (8). Taken as a whole the
XYY decisions reflect the deeply inbred skepticism of the criminal law for
nonculpability defenses. Substantial hurdles must be overcome to convince
any court that someone who committed a proscribed act should not be
punished for it.
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What then is the future of nonculpability defenses that are based on
genetic variables such as low MAOA, combined with relevant environmental
factors like severe childhood maltreatment? The very nature of genetic
evidence will likely make it difficult to meet traditional standards for
exculpation. One can imagine that most relevant genetic data will
demonstrate an increased predisposition among people with a particular
combination of genetic and experiential factors to engage in violent and
other criminal behavior but will not be able to establish a definitive
causal link between the genetic defect and the defendant's act. Genetic
data will probably be inadequate to meet criteria for an insanity defense
and may not even be sufficient to satisfy more lenient approaches, such as
the proposed defense of genetic determinism. Genetic data may even run
afoul of standards for admissibility of evidence, because guidelines such
as the Federal Rules of Evidence exclude testimony aimed solely at
demonstrating that the defendant has a propensity to behave in a particular
way. Successful defenses based on genetic factors are not very likely.
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Even if genetic predispositions are not exculpatory, they might be seen as
mitigating and be taken into account at sentencing. Indeed, a convicted
murderer in Georgia tried to take advantage of the potential mitigating
effect of genetic data soon after the Dutch study first documented a link
between the absence of MAOA and violence (9). Although the Georgia courts
declined to authorize the prisoner to be tested for MAOA activity at state
expense to establish a basis for appealing his death sentence—probably
because he offered no basis to believe that he might have the rare
condition reported in the Netherlands—many more such requests can be
anticipated in the wake of the dissemination of the Dunedin data. Oddly, at
present no reported cases exist in which genetic data of any sort have been
cited as the basis for mitigation at criminal sentencing. The most widely
discussed case is of questionable relevance; the Supreme Court of
California overturned the disbarment of an attorney, noting that evidence
that he had not been told of his "genetic predisposition to addiction" was
mitigating—although what role this comment really played in the Court's
decision is unclear (10).
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Should genetic propensities mitigate punishment for criminal behavior? The
answer to that question depends in part on whether one believes that
factors reducing but not eliminating one's capacity for self-control ought
to reduce moral responsibility for one's behavior. Moral philosophers
differ on this question, with some requiring an impairment of normal
deliberative processes or at least a repudiation of the desires that the
person finds difficult to control before they would accept an argument for
mitigation (6). In the end utilitarian considerations are likely to
determine how the courts deal with this issue. Unlike most mental
illnesses, genetic propensities for criminality are currently not
treatable. Hence, no clear means exists of reducing the risk presented by
these defendants. That leaves defense attorneys with the rather
unpersuasive argument that because their clients are more likely than most
people to offend—and presumably to reoffend—as a result of their genetic
endowment, they should be sentenced more leniently. Until effective
interventions emerge for any condition that serves as the basis for a
genetic claim for leniency, such arguments are not likely to make much
headway in the courts.
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Although I have focused on the use of genetic information for mitigating
punishment, it is worth noting that its impact at sentencing might run in
the opposite direction as well. Whether prosecutors can introduce genetic
evidence of a predisposition to criminality as an aggravating factor that
should lead to more severe punishment is an open question. In a small
number of states, such as Texas, which require prosecutors to establish
that defendants are likely to commit future acts of violence before the
jury can impose a death sentence, one can imagine prosecution efforts to
introduce MAOA levels in support of that contention. The power of the state
to test a defendant's genetic profile without his or her consent is another
issue that may well be subject to future litigation.
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We stand, in all likelihood, at the threshold of an era in which we will
see progressive growth in our knowledge of the genetic bases of behavior.
Genes that alone or in combination with environmental influences put
persons at high risk of violence and other crimes will be identified. Faced
with that prospect, it would behoove us to think through now how we believe
our criminal justice system should be responding to the inevitable dilemmas
that will arise.
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Footnotes
Dr. Appelbaum, who is editor of this column, is A. F. Zeleznik
distinguished professor and chair in the department of psychiatry at the
University of Massachusetts Medical School, 55 Lake Avenue North,
Worcester, Massachusetts 01655 (e-mail, appelbap@ummhc.org).
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References
1. Lombroso C: Crime: Its Causes and Remedies. Boston, Little, Brown, 1911 2. Wikin HA, Mednick SA, Schulsinger F, et al: Criminality, aggression, and intelligence among XYY and XXY men, in Biosocial Bases of Criminal Behavior. Edited by Mednick SA, Christiansen KO. New York, Gardner Press, 1977 3. Brunner HG, Nelen M, Breakefield XO, Ropers HH, van Oost BA. Abnormal behavior associated with a point mutation in the structural gene for monoamine oxidase A. Science 262:578–580, 1993 [Full Text] 4. Caspi A, McClay J, Moffitt TE, Mill J, Martin J, Craig IW, Taylor A, Poulton R Role of genotype in the cycle of violence by maltreated children. Science 297:851–854, 2002 [Full Text] 5. Stone RD: The cloudy crystal ball: genetics, child abuse, and the perils of predicting behavior. Vanderbilt Law Review 56:1557–1590, 2003 6. Wasserman D: Is there value in identifying individual genetic predispositions to violence? Journal of Law, Medicine, and Ethics 32:24–33, 2004 7. Johnson M: Genetic technology and its impact on culpability for criminal actions. Cleveland State Law Review 46:443–470, 1998 8. Coffey MP: The genetic defense: excuse or explanation? William and Mary Law Review 35:353–399, 1993 9. Mobley v State, 455 SE 2d 61 (Ga 1995) 10. Baker v State Bar of California, 781 P2d 1344 (Calif 1989) |
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