Crime psych- 1- What makes a criminal?

What makes a criminal (biological)

Criminal behaviour= an act which breaks/violates a law

Jeff Landrigan was a convicted murderer who found out on death row that his biological father (whom he had not seen since he was 6 months old) was also on death row in another state, cases like these suggest that there is potentially a faulty gene which predisposes individuals to criminal/violent behaviour. 

Family history studies:

Osborne & West (1982) found, when comparing the sons of criminal and non-criminal fathers, that 13% of the sons of non-criminal fathers had criminal convictions compared to 40% of sons with criminal fathers.

So it could be concluded from this if father is a criminal there appears to be an increased risk of son becoming one- however, another expl for this other than genetics could be SLT.

Even if we accept that the higher rate of criminality in the sons of criminal fathers is attributable to genetics, it is necessary to explain why 60% of them do not go on to commit crimes and why 13% of the sons of non criminal fathers did. Therefore, it seems unlikely that genetics can be the sole expl for criminal behaviour.

Twin studies:

If criminality is genetically inherited the concordance rates should be higher in MZ twins.

Early twin studies found higher concordance of criminality between MZ and DZ twins which supports the expl of a genetic influence.

However, much of this early research was flawed by: small samples and poor methods for determining zygocity (whether the twin pairs were MZ or DZ)

The most convincing studies come from Denmark, where researchers have access to extensive data on over 3,500 twin pairs.

Christiansen (1977) found MZ concordance rates of 35% compared to 13% for DZ twins.

Dalgard & Kringlen (1976) in Norway, found similar results of 26% in MZ twins and 15% for DZ twins. 

However, concordance is not even close to 100% which would be expected if criminality is genetic. There is a possibility that MZ twins are treated similarly which could account for the higher concordance rates i.e. nurture rather than nature.

Adoption studies:

In family and twin studies, the Ps live together so it is impossible to distangle the influence of nature or nurture. 

In adoption studies similarities between biological parents and their children suggest that genes are important whereas similarities between adoptive parents and their children suggest that the env is important. 

Researchers compare children born to criminal parents and raised in a diff en. If genetics are important then rates should be higher in children born to criminal parents and raised outside that env in comparison to control adoption children. 

Main findings: if biological parents have a criminal record, the % of sons with a criminal record is higher than if they didn't have a criminal father. 

Having adoptive parents with a criminal record also increases the chance of sons having a criminal record. The risk is even higher if both bio and adopted parents have a criminal record.

Conclusions…