Genetic

• Twin studies - Lange (1930)

  The importance of genes is illustrated by twin studies

  First criminal twin studies were conducted by Johannes Lange (1930) who investigated 13 MZ and 17 DZ twins where one of the twins in each pair had served time in prison

  Lange found that 10 of the MZ twins but only 2 of the DZ twins had a co-twin who was also in prison

  Lange concluded that genetic factors must play a predominant part in offending behaviour
• Adoption Studies - Crowe (1972)

  Found that adopted children who had a biological parent with a criminal record had a 50% risk of having a criminal record by the age of 18

  Whereas adopted children whose mothers didn’t have a criminal record only had a 5% risk
• Candidate Genes 


  Tilhonen et al (2014) - A genetic analysis of almost 900 offenders revealed abnormalities on two genes that may be associated with violent crime

  • MAOA / Warrior gene - controls dopamine and serotonin in the brain and has been linked to aggressive behaviour
  • CDH13 - linked to substance abuse and ADHD

  Within Finnish sample - individuals with this high risk combination were 13 times more likely to have a history of violent behaviour

  However this research is still in infancy and hasn’t been replicated
• Diathesis-Stress 


  If genetics do have some influence on offending, it seems likely that this is at least partly moderated by the effects of the environment

  A tendency towards criminal behaviour may come about through the combination of genetic predisposition and biological or psychological trigger - eg, being raised in a dysfunctional environment or having criminal role models