Criminology Notes – Unit 2
AC2 - Crime Theories
Biological Theory
- The basic idea behind all biological theories is that criminals are biologically
different than non-criminals and this difference makes them commit crimes;
people are born with criminal tendencies or have brain injuries that cause them
to act irrationally.
Four different types of biological explanations for criminality:
1) Genetic theories – see criminality as inherited
2) Physiological theories – focusing on criminal’s physical characteristics.
3) Brain injuries and disorders – that cause people to offend
4) Biochemical – involving hormones/substances that would make people offend.
Genetic Theories
- We have 46 chromosomes each as people
- Chromosomes are structures in cell nuclei which contain our genes.
- 23 from our mother, 23 from our father
- These chromosomes determine everything about us and are code for all the
structures in the body e.g. hair colour, eye colour.
Jacob’s XYY Theory
- There is a genetic condition in which a male has an extra (Y) chromosome, giving
a total of 47 chromosomes. Such a condition occurs every 1 in 1,000 male
births.
- Symptoms include Unusually tall, impaired intellectual development, weak
muscle tone and delayed speech.
- Some XYY men have an increase of aggression due to this extra chromosome.
- Jacob et al (1965) published their findings of a chromosome survey conducted at
a maximum-security hospital, 9 out of 315 prisoners had the extra Y
chromosome.
- There are 15 people per 1,000 with XYY in prisons, and 1 per 1000 in the general
population.
- The presence of an extra Y chromosome can cause criminal behaviour.
, - Case study John Wayne Gacy = was a criminal known as ‘killer clown’ and
sexually abused young boys and killed them, he had an extra Y chromosome.
Strengths =
- Jacobs et al found an association between XYY syndrome and offenders
imprisoned for violent behaviour. (research support)
- Price and Whatmore found some links between the syndrome and property
crime. (research support)
- Adler et al (2007) indicated that it is possible that aggressive and violent
behaviour is at least partly determined by genetic factors. (research support)
- Explains why criminal behaviour may be caused if the criminal has a positive
environment when growing up.
Weaknesses =
- XYY males are tall and well built, so they fit the stereotype of ‘violent offenders’
and get labelled as such by the courts, so they are more likely to get a prison
sentence. Therefore, XYY males are over-represented in samples drawn from
prisoners and this overstates the importance of the syndrome as a possible
cause of crime.
- Does not explain crimes which are committed by individuals who do not suffer
from the XYY syndrome, this cannot fully explain why crime is committed.
The Warrior Gene
- Dutch Professor, Han Brunner made the discovery of an ‘MAOA’ gene mutation
in 1993 when he studied a Dutch family whose male generations displayed
extreme violent aggression
, - Nine of the males from the family were studied through biologically testing; they
all were missing the MAOA gene completely.
- MAOA gene is designed to remove the stress hormones from our body, when it
does not work, we are in a state of constant stress/aggression.
- Therefore, the MAOA gene mutation may cause crime.
Note: You will never be asked a question directly on the warrior gene, but it is
useful to use in other questions.
Twin Studies
- Monozygotic twins = ‘Identical Twins’, they share 100% of the same genetics.
- Dizygotic twins = ‘Fraternal Twins’, they share 50% of the same genetics.
Christiansen’s study of Twins
- Compared 3,596 pairs of Monozygotic Twins
- He found a 52% concordance rate, this means 52% of the cases when one twin
had a conviction, the other one did too.
- Afterwards, he conducted the same study but with dizygotic twins, he found a
22% concordance rate.
- We can conclude that as both monozygotic and dizygotic twins are raised in the
same environment, as monozygotic has a higher concordance rate genes must
play a role in criminality.
Strengths =
- Twin studies help isolate the role of genetics in behaviour, providing insights into
the heritability of certain traits (e.g., aggression) expanding our understanding of
why crime may be committed.
- The studies involved a large sample size, the number of twin pairs was 3,596,
increasing the reliability and generalizability of the results.
Weaknesses =
- Does not fully explain crime, if genetics were the sole reason for crime the
concordance rate would be 100% for monozygotic twins, therefore there must
be other factors this theory does not account for.
, - Assumes that identical twins experience the same environment, which may not
always be the case, leading to potential biases in the findings.
Twin Adoption Studies
Cloninger et al. (1982)
- Examined adopted twins who were adopted by different parents, it studied the
criminal backgrounds of the biological parents and the environments of the
adoptive families they were raised in.
- 27% of adopted individuals whose biological parents had criminal records
went on to commit crimes.
- They found a higher likelihood of criminal behaviour in adoptees whose
biological parents had criminal histories, despite the differences of the adoptive
families.
- Therefore, genetic factors play a role in criminal behaviour rather than
environmental factors.
Strengths =
- By comparing the criminal behaviour of biological and adoptive parents, the
study could better isolate genetic vs. environmental influences, being able to
explain the understanding of why people may commit crime.
Weaknesses =
- The study was conducted in Denmark, which may limit the generalizability of the
results to other cultures or countries with different social structures or laws.
AC2 - Crime Theories
Biological Theory
- The basic idea behind all biological theories is that criminals are biologically
different than non-criminals and this difference makes them commit crimes;
people are born with criminal tendencies or have brain injuries that cause them
to act irrationally.
Four different types of biological explanations for criminality:
1) Genetic theories – see criminality as inherited
2) Physiological theories – focusing on criminal’s physical characteristics.
3) Brain injuries and disorders – that cause people to offend
4) Biochemical – involving hormones/substances that would make people offend.
Genetic Theories
- We have 46 chromosomes each as people
- Chromosomes are structures in cell nuclei which contain our genes.
- 23 from our mother, 23 from our father
- These chromosomes determine everything about us and are code for all the
structures in the body e.g. hair colour, eye colour.
Jacob’s XYY Theory
- There is a genetic condition in which a male has an extra (Y) chromosome, giving
a total of 47 chromosomes. Such a condition occurs every 1 in 1,000 male
births.
- Symptoms include Unusually tall, impaired intellectual development, weak
muscle tone and delayed speech.
- Some XYY men have an increase of aggression due to this extra chromosome.
- Jacob et al (1965) published their findings of a chromosome survey conducted at
a maximum-security hospital, 9 out of 315 prisoners had the extra Y
chromosome.
- There are 15 people per 1,000 with XYY in prisons, and 1 per 1000 in the general
population.
- The presence of an extra Y chromosome can cause criminal behaviour.
, - Case study John Wayne Gacy = was a criminal known as ‘killer clown’ and
sexually abused young boys and killed them, he had an extra Y chromosome.
Strengths =
- Jacobs et al found an association between XYY syndrome and offenders
imprisoned for violent behaviour. (research support)
- Price and Whatmore found some links between the syndrome and property
crime. (research support)
- Adler et al (2007) indicated that it is possible that aggressive and violent
behaviour is at least partly determined by genetic factors. (research support)
- Explains why criminal behaviour may be caused if the criminal has a positive
environment when growing up.
Weaknesses =
- XYY males are tall and well built, so they fit the stereotype of ‘violent offenders’
and get labelled as such by the courts, so they are more likely to get a prison
sentence. Therefore, XYY males are over-represented in samples drawn from
prisoners and this overstates the importance of the syndrome as a possible
cause of crime.
- Does not explain crimes which are committed by individuals who do not suffer
from the XYY syndrome, this cannot fully explain why crime is committed.
The Warrior Gene
- Dutch Professor, Han Brunner made the discovery of an ‘MAOA’ gene mutation
in 1993 when he studied a Dutch family whose male generations displayed
extreme violent aggression
, - Nine of the males from the family were studied through biologically testing; they
all were missing the MAOA gene completely.
- MAOA gene is designed to remove the stress hormones from our body, when it
does not work, we are in a state of constant stress/aggression.
- Therefore, the MAOA gene mutation may cause crime.
Note: You will never be asked a question directly on the warrior gene, but it is
useful to use in other questions.
Twin Studies
- Monozygotic twins = ‘Identical Twins’, they share 100% of the same genetics.
- Dizygotic twins = ‘Fraternal Twins’, they share 50% of the same genetics.
Christiansen’s study of Twins
- Compared 3,596 pairs of Monozygotic Twins
- He found a 52% concordance rate, this means 52% of the cases when one twin
had a conviction, the other one did too.
- Afterwards, he conducted the same study but with dizygotic twins, he found a
22% concordance rate.
- We can conclude that as both monozygotic and dizygotic twins are raised in the
same environment, as monozygotic has a higher concordance rate genes must
play a role in criminality.
Strengths =
- Twin studies help isolate the role of genetics in behaviour, providing insights into
the heritability of certain traits (e.g., aggression) expanding our understanding of
why crime may be committed.
- The studies involved a large sample size, the number of twin pairs was 3,596,
increasing the reliability and generalizability of the results.
Weaknesses =
- Does not fully explain crime, if genetics were the sole reason for crime the
concordance rate would be 100% for monozygotic twins, therefore there must
be other factors this theory does not account for.
, - Assumes that identical twins experience the same environment, which may not
always be the case, leading to potential biases in the findings.
Twin Adoption Studies
Cloninger et al. (1982)
- Examined adopted twins who were adopted by different parents, it studied the
criminal backgrounds of the biological parents and the environments of the
adoptive families they were raised in.
- 27% of adopted individuals whose biological parents had criminal records
went on to commit crimes.
- They found a higher likelihood of criminal behaviour in adoptees whose
biological parents had criminal histories, despite the differences of the adoptive
families.
- Therefore, genetic factors play a role in criminal behaviour rather than
environmental factors.
Strengths =
- By comparing the criminal behaviour of biological and adoptive parents, the
study could better isolate genetic vs. environmental influences, being able to
explain the understanding of why people may commit crime.
Weaknesses =
- The study was conducted in Denmark, which may limit the generalizability of the
results to other cultures or countries with different social structures or laws.
