Cognitive abilities such as
impulse control and forward
planning are some of the last
aspects of the brain to
develop.
An ABI (acquired brain injury) could
disrupt this development, meaning that
the individual may fail to move beyond
reckless and risk-taking behaviour which
is sometimes associated with childhood.
This may lead to increased crime and
anti-social behaviour.
Williams et al found that 60% of a sample of 196 inmates
from a UK prison recalled a history of one or more brain
injuries in their youth. Furthermore, they found that this
group tended to be younger at the time of their first
offence, had higher rates of recidivism, and had spent more
time in prison over the last five years than the rest of the
sample.
Injuries to the brain may also
destabilise mood, concentration
and decision-making, meaning
that offending behaviour may be
more likely.
Fazel et al found that there was a higher percentage
of Swedish individuals who suffered a traumatic
brain injury and committed a violent crime
compared to a group of matched controls,
suggesting that physical trauma to the brain may
cause violent crimes.
However, supporting studies often show a correlation between
the two, but this does not necessarily show causation. Other
variables may have had an influence, for example individuals
who have sustained serious head injuries are more likely to
experience mental illness, or be alcohol/drug abusers. These
factors may predispose an individual to offend, rather than it
being the brain injury itself.
Amygdala and aggression
The amygdala is located in the
brain's limbic system which
helps direct how we react to
threatening situations.
Abnormalities in the size,
structure and activity of the
amygdala correlates with an
increase in aggression, which
could make criminal behaviour
more likely.
Raine observed that there was a reduced
level of activity in several areas of the
brains of NGRIs (murderers), including the
left amygdala. This shows that there is a
relationship between the amygdala and
criminal behaviour.
Pardini found that a group of 26-year-old
men with a reduced amygdala size were
3x more likely to be aggressive, violent
and show psychopathic traits compared
to a group with a normal-sized amygdala.
A weakness of this idea is that the amygdala is implicated with other
regions of the brain. It is suggested that the amygdala does not operate
alone, but with other areas of the brain, such as the OFC which is a part
of the frontal lobe and is thought to regulate self control - its reduced
functioning is associated with increased aggression and violent
outbursts. This means that the influence of the amygdala on aggression
and crime is hard to disentangle.
XYY syndrome
About 1 in 1000 males are born
with an extra Y chromosome,
which is known as having XYY
syndrome.
Males with XYY syndrome are typically
taller than average, have lower intelligence,
can be more impulsive and experience
behavioural difficulties. This may lead them
to be more likely to commit crimes or to
partake in anti-social behaviour.
Early studies reported a connection between XYY syndrome
and aggression and crime. Jacobs et al found that men with
XYY were over-represented in prison populations compared
to the general population. The idea of a criminal
chromosomal pattern was widely publicised at the time.
However, there is a lack of evidence to support this supposed
relationship. Re and Birkhoff conducted a meta-analysis using data
from over 50 years and concluded that there is no link between XYY
and offending behaviour. It is suggested that where there is a
prevalence of XYY males in prison populations it may be more due
to social factors, such as XYY males finding it more difficult to
integrate into society and find work. The lack of evidence therefore
suggests XYY is not a credible explanation of crime.
Application
Biological research could
lead to new ways in
assessing criminal
culpability.
Williams, for example, argued for an increased
awareness surrounding brain injuries throughout the
criminal justice system, including a screening of young
people when they first offend. They recommended
that neural injuries should be treated the same way
as mental illness in court, and that it should result in a
reduced punishment as the individual is less
responsible for their crime.