Genetic explanation

• The assumption suggests that offenders inherit a gene or combination of genes that predispose them to commit crime
• Christiansen studied over 3500 twin pairs in Denmark finding a concordance for offender behaviour of 35% males and 13% for DZ males (slightly lower rates for females). This supports a genetic component in reoffending
• Crowe found that adopted children who had a biological mother with a criminal record had a 50% risk of having a criminal record at age 18. Whereas adopted children whose mother didn't have a criminal record only had a 5% risk
• Genetic analysis of 800 Finnish offenders by Tihohen suggested 2 genes that may be associated with violent crime

  • MAOA gene regulates serotonin and is linked to aggressive behaviour
  • CDH-13 gene linked to substance abuse and ADHD
• Tihonens analysis found that about 5-10% of all severe violent crime in Finland is attributable to the MAOA and CDH-13 genotypes
• If genes influence offending, this influence is likely to be at least partly moderated by environmental factors
• Diathesis stress suggests that a tendency to offending behaviour is due to a combination of:

  • genetic predisposition (diathesis)
  • biological or psychological stressor
• One limitation of twin studies is assuming equal environments. Often assumed that environmental factors are the same for MZ and DZ twins because they experience similar environments. However, because MZ twins look identical, people tend to treat them more similarly which, in turn, affects their behaviour. Therefore higher concordance rates for MZ may be because they are treated more similarly than DZs suggesting conclusions lack validity
• One strength is the support for a diathesis stress model of offending. Mednick et al studied 13000 Danish adoptees having at least one court conviction. Conviction rates 13.5% (biological or adoptive parents had no convictions), 20% (one biological parent), 24.5% (both adoptive and biological parents). This data suggests that both genetic inheritance and environment influence criminality - supporting the diathesis stress model of crime
• A counterpoint to the diathesis stress model of offending is low generalisability. This only accounts for petty crimes and doesn't account for violent behaviours