Genetic

• genetic explanation


  suggests that people can inherit a predisposition to commit crime
• what do genetic explanations look for?

  evidence of a family history of criminal behaviour, suggesting a genetic basis
• Two types of studies used to test the genetic explanations

  Twin studies and adoption studies
• Rosanoff et al (1934)

  looked at 97 male twin pairs

  concordance rates:

  • MZ: 67%
  • DZ: 13%
• Crowe (1972)

  looked at criminal records of people who had a biological mother with a criminal record, and had all been adopted

  findings:

  • 50% with a biological mother with a criminal record had a criminal record themselves
  • 5% of the control group had a criminal record where their biological mother did not have one
• MAOA gene 


  an enzyme that breaks down neurotransmitters in the brain such as serotonin and dopamine
• variants of the MAOA gene

  • MAOA H
  • MAOA L
• link between MAOA L and crime

  people with low levels of MAOA had high levels of serotonin, which is associated with aggression and impulsivity
• Brunner et al (1993)

  • case study of a large family, many of which had criminal records
  • average IQ was 85
  • found males have a genetic condition called Brunner Syndrome that results in lower intelligence and low levels of MAOA
• Tilhonen et al (2015)

  • genetic analysis of 800 Finnish offenders
  • 5-10% of severe violent crime in Finland is attributable to 2 genes: MAOA and CDH13
• diathesis stress model

  proposes that a tendency towards offending may be due to a combination of genetic predisposition and psychological triggers
• Caspi et al (2002)

  • longitudinal study on 1000 males
  • 12% of males with MAOA-L were responsible for 44% of violent crimes

  however they were all mistreated or abused as children