Genetic Theories of Criminality

• Twin Studies:

  • Genetic Theories have used studies of identical twins as a way to test theory of criminality
  • This is because identical twins share exactly the same genes so if one is criminal, the other twin is ought to be criminal too
  • Evidence for this comes from Christiansens Study on 3586 twins in Denmark which found there was a 52% chance that if one identical twin has a criminal conviction then the other one would too
  • Among non-identical twins it was only a 22% chance.
  • A later study by Ishikawa and Raine found similar findings.
• Adoption Studies:

  • Mednick‘s Theory/Study supports a genetic explanation for the cause of crime because that sone were more likely to have a criminal record if their biological parent had one
  • Genetic parents having a criminal record increased the adopted son being a criminal by 20%
  • However, if the adoptive parents have had a criminal record, the chance of the adoptive child having one was only 14%
• Jacob’s XYY Study:

  • Jacob claimed that men with XYY syndrome are more aggressive, taller, well built, and potentially violent than other criminals.
  • Price and Whatmore found XYY males to be more immature and unstable and more likely to commit crimes.