Genetic

• Genetic mutation:


  Family members that share a genetic mutation are predisposed to committing crime. 

  Price et al: high number of violent male criminals had XXY chromosome pattern which leads to increase testosterone and therefore increased aggression. 
• Candidate genes: 


  MAOA gene- linked to aggressive behaviour.

  CDH13- linked to ADD and substance abuse.

  With both genes an individual is 13x more likely to commit a crime suggesting that offending is polygenic. 
• Twin studies:


  Concordance rates for offender behaviour is 35% for identical twin (MZ) males and 13% for non-identical twin (DZ) males (with lower rates for females). This indicates that it’s not just behaviour that might be inherited but the underlying predisposition traits. 

  Adopted children whose biological mother had a criminal record had a 50% risk of having a criminal record by the age of 18, whereas if an adopted child didn’t have a biological mother who had a criminal record only had a 5% risk.
• strength of genetic explanation is its high scientific crediblity. Genetic testing and PET scans are used by biologists to investigate the causes of offending behaviour. These methods are highly credible because theyre objective, avoiding issues associated with subjective research. methods are falsifiable, meaning that it’s possible for researchers to prove or disprove them. This suggests that  research and theories derived from biology are more accurate and credible than the work from other approaches, such as psychodynamic and cognitive theories, which focus on largely untestable concepts. 
• weakness of genetic explanation is issue of twin studies assuming there is equal environment. assumed by researchers studying twins that environmental factors are held constant as twins are brought up together so must experience similar environments. However, this ‘shared environment assumption’ may apply much more to MZ twins than DZ twins because MZ twins look identical and people (esp parents) tend to treat them more similarly which affects their behaviour. Therefore higher concordance rates for MZs twins in twin studies may simply be because they are treated more similarly than DZ twins.