genetic explanations

• Genetic explanations = would-be offenders inherit a gene that predisposes them to commit crime
• Christiansen studied over 3500 twin pairs in Denmark, and found concordance rates for offender behaviour of 35% for identical male twins and 13% for non-identical male twins. Offender behaviour was checked against Danish police records. This data indicates that it is not just the behaviour that might be inherited but the underlying predisposing traits.
• Crowe found that adopted children whose biological mother had a criminal record had a 50% risk of having a criminal record by 18, whereas adopted children whose biological mother didn’t have a criminal record only had a 5% risk.
• A genetic analysis of 800 Finnish offenders by Tiihonen suggested that two genes (MAOA and CDH13) may be associated with violent crime.
• The MAOA gene regulates serotonin in the brain and has been linked to aggressive behaviour.
• The CDH13 gene has been linked to substance abuse and ADHD.
• The analysis found that about 5-10% of all severe violent crime in Finland is attributable to the MAOA and CDH13 genotypes.
• One limitation of using twin studies as genetic evidence is the assumption of equal environments. It is assumed by researchers that because twins grew up together they would experience the same environment. However, this applies more to MZ twins than DZ twins as people, especially parents, are more likely to treat identical twins the same which in turn affects their behaviour. Therefore high concordance rates in MZ twins may simply be because they are treated much more similarly than DZ twins.
• One strength is support for the diathesis-stress model of offending. A study of 13,000 Danish adoptees was conducted by Mednick et al.
• Mednick found that when neither the biological nor adoptive parents had convictions, the percentage of adoptees that did was 13.5%. This figure rose to 20% when either of the biological parents had convictions, and 24.5% when both adoptive and biological parents had convictions. This shows genetic inheritance plays an important role in offending but environmental influence is clearly also important, providing support for the diathesis-stress model of crime.
• Diathesis-stress model = a tendency towards offending behaviour may come from a combination of genetic predisposition and a psychological trigger.