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Introduction to Human

Behavioral Genetics

Unit 8:

Summary, Public Policy &

Prospects

Behavioral Genetics, the Law and Personal Responsibility: Part I

(Module C)

Behavioral genetics and the law

• Most legal systems are based on the assumption that we are generally responsible for our behavior

• There have not been many uses of behavioral genetic research in the courts

• When introduced it has typically been used by the defense in an attempt to absolve or mitigate responsibility

Continuum of Genetic Influence

Mendelian (Single-gene) Diseases: High Genotype Phenotype Correlation Specific Genetic Etiology – e.g., Huntington Disease

Multifactorial (Multi-gene) Diseases: Modest to Moderate Genotype Phenotype Correlation Genetic Heterogeneity – e.g., Schizophrenia

GENETIC

ACQUIRED

Non- (or Low-) Heritable Diseases: Little/No Genotype Phenotype Correlation – e.g., Head trauma, brain tumor

Does Continuum of Genetic Influence Implicate

Complementary Continuum of Responsibility?

Mendelian (Single-gene) Diseases:

Multifactorial Diseases:

GENETIC

ACQUIRED

Non- (or Low-) Heritable Diseases:

LOW PERSONAL

RESPONSIBILITY?

HIGH PERSONAL

RESPONSIBILITY?

Genetics in the courtroom?

The XYY male • Usually tall and slender

• Slightly lower IQ than average

• Produce higher levels of testosterone than XY males

• In 1965 & 1966 Pat Jacobs reported males with XYY were over-represented in British penal institutes

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Richard Speck

• On July 14, 1966 murdered 8 student nurses in Chicago

• He was somewhat tall and some speculated he might have an XYY karyotype

• Media erroneously reported he was XYY

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A more successful use of a ‘genetic

defense’? The case of Bradley Waldroup

• On Oct 16, 2006 shot his ex-wife’s best friend 8 times, killing her, and attacked his ex-wife with a machete

• Defense presented evidence that Waldroup carried a “high-risk” MAO-A allele and had a history of childhood abuse

A focus on MAO-A

• Serotonin and aggression: Animals with no MAO-A have high levels of brain serotonin and are aggressive

• Dutch pedigree: Males affected with impulsive aggression had low levels of MAO-A activity

• Nonsense mutation: In position 936 a C to T mutation changes a glutamine (CAG) codon to a stop (TAG) codon

Brunner, H. G., et al. (1993). Abnormal behavior associated with a point mutation in the structural gene for monoamine oxidase-A Science, 262(5133), 578-580.

Another MAO-A variant was found to interact with childhood

history of maltreatment in predicting antisocial behavior

Published by AAAS Caspi, A., et al. (2002). Role of genotype in the cycle of violence in maltreated children. Science, 297(5582), 851-854.

The MAO-A gene has gained quite

a reputation

• The murder gene: http://www.duhaime.org/LegalDictionary/M/MurderGene.aspx

• The warrior gene: http://news.brown.edu/pressreleases/2009/01/hotsauce

• The rage gene: http://channel.nationalgeographic.com/channel/videos/born-to-rage2/

Please take a look at the first couple of minutes of the documentary:

http://channel.nationalgeographic.com/channel/videos/born-to-rage2/

That begins with the question:

“Are some people born violent?”