Case Study; Raine et al (1997); Brain Abnormalities in Murderers Indicated by Positron Emission Tomography

Aim

• to use PET scans to investigate brain differences between murderers who were pleading not guilty by reason of insanity (NGRI) and non-murderers

Experiment type

Quasi-experiment

• the independent variable was not manipulated as the difference between the focus and the control groups was pre-existent (murderer and non-murderer)

Sample type

Opportunity sample

• all of the participants were at the University of California, where Raine was likely working

Experimental design

Matched pairs

• both groups shared similar characteristics and were matched regarding age and gender

  • there were six schizophrenics in each group

Experimental group

• 41 in total

• 39 males and 2 females

• mean age of 34.3 years

• reasons for referral included history of brain damage

• no subject was taking any medication

Control group

• 41 in total

• 39 males and 2 females

• mean age of 31.7 years

• normal controls had been screened for health by physical exam, medical history and a psychiatric interview

• no subject was taking any medication

Procedure; Step 1

• ten minutes before fluorodeoxyglucose (FDG) injection, participants were given practice trials on a continuous performance task (CPT)

Procedure; Step 2

• thirty seconds before FDG injection, the CPT was started so that initial task novelty would not interfere with the results of the PET scan

Procedure; Step 3

• FDG tracer was injected into each participant

Procedure; Step 4

• FDG tracer was taken up by the brain for a 32 minute period during which the participant completed a CPT

Procedure; Step 5

• participant was then transferred to a PET scanner where the brain was scanned in 10mm horizontal slices

Findings

• the murderers had significantly lower parietal glucose metabolism compared to the control group, especially in the left angular gyrus

• the murderers had significantly higher occipital lobe glucose metabolism than controls

• the murderers showed an abnormal asymmetry of activity with reduced left and increased right activity in the amygdala and hippocampus

• no significant differences in the temporal lobe glucose metabolism and in the amount of midbrain and cerebellum activity between the murderers and controls

Conclusions

• the findings cannot be used to demonstrate that violence is determined by biology alone

• social, psychological, cultural and situational factors also play important roles in a predisposition to violence

• findings cannot be generalised to other types of violent offenders

• data does not demonstrate that murderers pleading NGRI are not responsible for their actions

• data does not demonstrate that PET scans can be used as a diagnostic technique

• findings do not establish a causal link between brain dysfunction and violence

Ethics (positive)

confidentiality - names of participants were not revealed

Ethics (negative)

consent - murderers were pleading NGRI due to brain injuries so they could not give informed consent and 6 participants (in each group) were unmedicated schizophrenics

protection from harm - physical harm from PET scans and radioactive tracer

Social (positive)

• Raine tried to reduce negative impacts with his conclusions'

• provides evidence that suggests more support is needed for similar cases

Social (negative)

• may lead to feelings of injustice

• prejudice and discrimination

  • removal of human rights

• bias applied to other cases (generalisation)

Evaluation Point: One strength is that PET scans were used as a research method

Evidence; PET scans allowed detailed looks at different sections of the brain

Explain; scans are scientific and provide solid, observable evidence of results meaning that Raine could show some sort of cause-and-effect relationship between brain areas and violent crime

Link; PET scans allow researchers to examine different areas of the brain

Evaluation Point: One limitation is that alternative evidence has suggested that brain dysfunction may not be the sole cause of violence

Evidence; Raine pointed out that findings do not show violence is due to biology alone, other factors such as upbringing must influence violence

Explain; James Fallon found that he had criminal genes but he didn't become a criminal as he had positive childhood experiences

Link; experience can influence criminality as Fallon, despite having the criminal genes, didn't become a criminal

Evaluation Point: One limitation is that the sample may not be representative of criminals

Evidence; this sample only covers one type of violent offender (murderers)

Explain; many violent crimes do do not involve murder e.g. robbery, so conclusions are restricted to a very specific group of criminals

Link; results can only be generalised to specific crimes. this can lead to discrimination against people with different brain function

Evaluation Point: One limitation is the use of Quasi experiments as the IV is not manipulated

Evidence; the IV was pre-existent, the murderers had already committed the crime

Explain; since the murderer had already committed the crime, it is impossible to determine whether brain dysfunction cause the murder or if it was pre-existent brain function

Link; we cannot draw causal conclusions from this research, people may misinterpret these findings and assume that criminal behaviour is predetermined which may have negative consequences for the individuals with this brain dysfunction