AC2.1 - Describe Biological Theories of Crime
Genetic Theories
XYY Theory:
- This theory suggests that crime may be attributed to chromosomal abnormality
- XYY men are called super males - there is a suggestion that they are more
aggressive and more inclined to be violent (Jacob et al. - 1965)
- There are also studies to show that XYY men are over represented in the prison
population. There are 15 sufferers per 1000 in the prison population, compared to 1
in 1000 in the general population.
- The serial killer John Wayne Gacy is thought to have had XYY syndrome. He
sexually assaulted and killed 33 men in the USA
Twin Studies:
- These studies support the idea that an inheritable trait may cause criminal behaviour
- Identical twins are monozygotic (MZ) as they are from one fertilised egg meaning
they share 100% of DNA, whereas dizygotic (DZ) twins only share 50% of DNA
- Johannes Lange found that MZ twins had a much higher degree of concordance than
DZ twins for criminal behaviour.
- Ten of 13 MZ twins had both served prison, whereas only two of the 17 DZ twins had
such concordance.
- Christiansen found a concordance rate of 35% for MZ twins and 13% for DZ male
twins. He also found a concordance rate of 21% for MZ twins and 13% for DZ female
twins
Adoption Studies:
- The comparison of criminals with both their biological and adoptive parents.
- Hutchings and Mednick studied 1,145 male adoptees in Denmark who had been
adopted between 1924 and 1947
- 36.2% of adoptees were likely to have a criminal record who had both biological and
adoptive fathers with criminal records, 21.4% chance if only biological, 11.5% chance
if only adoptive, 10.5% if neither father had a criminal record.
- This shows a genetic link to criminal behaviour, as even those who no longer lived
with their criminal parents still were more likely to commit crime.
Physiological Theories
Lombroso:
- Tried to relate certain characteristics such as jaw size, to a person’s tendency to
commit crime.
- He was an Italian university professor and criminologist and was inspired by
evolutionary and genetical studies in the 19th century
Genetic Theories
XYY Theory:
- This theory suggests that crime may be attributed to chromosomal abnormality
- XYY men are called super males - there is a suggestion that they are more
aggressive and more inclined to be violent (Jacob et al. - 1965)
- There are also studies to show that XYY men are over represented in the prison
population. There are 15 sufferers per 1000 in the prison population, compared to 1
in 1000 in the general population.
- The serial killer John Wayne Gacy is thought to have had XYY syndrome. He
sexually assaulted and killed 33 men in the USA
Twin Studies:
- These studies support the idea that an inheritable trait may cause criminal behaviour
- Identical twins are monozygotic (MZ) as they are from one fertilised egg meaning
they share 100% of DNA, whereas dizygotic (DZ) twins only share 50% of DNA
- Johannes Lange found that MZ twins had a much higher degree of concordance than
DZ twins for criminal behaviour.
- Ten of 13 MZ twins had both served prison, whereas only two of the 17 DZ twins had
such concordance.
- Christiansen found a concordance rate of 35% for MZ twins and 13% for DZ male
twins. He also found a concordance rate of 21% for MZ twins and 13% for DZ female
twins
Adoption Studies:
- The comparison of criminals with both their biological and adoptive parents.
- Hutchings and Mednick studied 1,145 male adoptees in Denmark who had been
adopted between 1924 and 1947
- 36.2% of adoptees were likely to have a criminal record who had both biological and
adoptive fathers with criminal records, 21.4% chance if only biological, 11.5% chance
if only adoptive, 10.5% if neither father had a criminal record.
- This shows a genetic link to criminal behaviour, as even those who no longer lived
with their criminal parents still were more likely to commit crime.
Physiological Theories
Lombroso:
- Tried to relate certain characteristics such as jaw size, to a person’s tendency to
commit crime.
- He was an Italian university professor and criminologist and was inspired by
evolutionary and genetical studies in the 19th century
