Lecture Notes: 3.3. Forensic Psychology (Elective)
Week 1
Lecture I
Legal aspects of a crime:
• Actus Reus (criminal act, or lack of an act)
• Mens Rea (intent, willingness)
Psychiatric Defences – if accepted by the court, the charge is reduced from murder to
manslaughter
Þ diminished responsibility (provocation)
o “Where a person kills or is a party to the killing of another, he shall not be convicted
of murder if he was suffering from such abnormality of mind as substantially
impaired his mental responsibility for his acts and omissions in doing or being a
party to the killing.”
Þ infanticide
o Where a woman by any wilful act or omission causes the death of her child, being a
child under the age of 12 months, but at the time of the act or omission the balance of
her mind was disturbed by reason of her not having fully recovered from the effect
of giving birth to the child or by reason of the effect of lactation consequent upon the
birth of the child, then, notwithstanding that the circumstances were such that but for
this Act the offence would have amounted to murder, she shall be guilty of felony, to
wit of infanticide, and may for such offence be dealt with and punished as if she had
been guilty of the offence of manslaughter of the child.
Þ automatism – accused lacked intent (mens rea) or act was involuntary and beyond the
control of the individual's mind
o insane automatism – e.g.: epilepsy, narcolepsy, dissociative state
o sane automatism – e.g.: reflex, sleepwalking, insulin induced hypoglycaemia, head
injury, intoxication
Lecture II
Family Studies
Correlate the degree of genetic relatedness (how many genes do family members share), with
the degree of personality similarity à More similar to your sibling, than your mom, than your
aunt etc.
Assumption: if a trait is highly heritable, then family members who are more related should be
more similar on that trait
Twin Studies
reflects the proportion of phenotypic (behavioural variance) that can be attributed to genotypic
(genetic) variance
General Findings (Twin Studies)
• Most genetic effects upon antisocial behaviour increase with age and shared
environmental effects decrease
• Early-onset persistent antisocial behaviour is more heritable than (later-onset) conduct
disorder
• Family environment is relevant for the initiation and early maintenance of aggression
(particularly in men), but its effect fades
, • Some genes influence antisocial behaviour across the entire lifespan, and others only in
adolescence and adulthood
Grey matter – neurons
White matter – connectivity
Damage to the PFC à associated with aggressive and/or violent behavioural histories
• Strongest evidence for an association between PFC dysfunction and impulse subtype
of aggressive behaviour
PFC study
APD group – lower grey matter volume in the PFC; White matter – not affected
Fear inhibition
• Impaired fear response – don’t feel fear as normal people à increased likelihood to
engage in criminal behaviour
Heart rate – APD did not show an increase in their heart rate
APD also did not show skin conductance, i.e.: sweating
• 5min to prepare a speech about “your flaws as a human being”
Age-Crime curve
Most of us fall into the adolescence limited anti-social behaviour
Limbic system
• Primary instinct part of the brain
Amygdala
• Emotions
• How we process emotional stimuli
• Overstimulation of the amygdala à violent, aggressive behaviour
, • Lesions of the amygdala à flat affect, not many peaks/lows in emotions, emotional
stimuli do not “stick” à could lead to violence
prefrontal dysfunction is associated with aggressive and/or violent behavioural histories
• lower prefrontal activity, decreased grey matter volume
• evidence is strongest for an association between prefrontal dysfunction and an
impulsive subtype of aggressive behaviour
temporal lobe dysfunction, particularly left-sided medial-temporal (subcortical) activity, is
associated with aggression and/or violence
the relative balance of activity between the prefrontal cortex and the subcortical structures is
associated with impulsive aggression and/or violence
• reduced prefrontal functioning relative to subcortical functioning was characteristic of
those who commit impulsive acts of aggression and/or violence
• by contrast, aggression and/or violence of a predatory nature was not related to reduced
prefrontal and/or subcortical ratios.
traumatic brain injuries precede violence and law-enforcements contact
• could be because of abuse (risk factor)
Week 1
Lecture I
Legal aspects of a crime:
• Actus Reus (criminal act, or lack of an act)
• Mens Rea (intent, willingness)
Psychiatric Defences – if accepted by the court, the charge is reduced from murder to
manslaughter
Þ diminished responsibility (provocation)
o “Where a person kills or is a party to the killing of another, he shall not be convicted
of murder if he was suffering from such abnormality of mind as substantially
impaired his mental responsibility for his acts and omissions in doing or being a
party to the killing.”
Þ infanticide
o Where a woman by any wilful act or omission causes the death of her child, being a
child under the age of 12 months, but at the time of the act or omission the balance of
her mind was disturbed by reason of her not having fully recovered from the effect
of giving birth to the child or by reason of the effect of lactation consequent upon the
birth of the child, then, notwithstanding that the circumstances were such that but for
this Act the offence would have amounted to murder, she shall be guilty of felony, to
wit of infanticide, and may for such offence be dealt with and punished as if she had
been guilty of the offence of manslaughter of the child.
Þ automatism – accused lacked intent (mens rea) or act was involuntary and beyond the
control of the individual's mind
o insane automatism – e.g.: epilepsy, narcolepsy, dissociative state
o sane automatism – e.g.: reflex, sleepwalking, insulin induced hypoglycaemia, head
injury, intoxication
Lecture II
Family Studies
Correlate the degree of genetic relatedness (how many genes do family members share), with
the degree of personality similarity à More similar to your sibling, than your mom, than your
aunt etc.
Assumption: if a trait is highly heritable, then family members who are more related should be
more similar on that trait
Twin Studies
reflects the proportion of phenotypic (behavioural variance) that can be attributed to genotypic
(genetic) variance
General Findings (Twin Studies)
• Most genetic effects upon antisocial behaviour increase with age and shared
environmental effects decrease
• Early-onset persistent antisocial behaviour is more heritable than (later-onset) conduct
disorder
• Family environment is relevant for the initiation and early maintenance of aggression
(particularly in men), but its effect fades
, • Some genes influence antisocial behaviour across the entire lifespan, and others only in
adolescence and adulthood
Grey matter – neurons
White matter – connectivity
Damage to the PFC à associated with aggressive and/or violent behavioural histories
• Strongest evidence for an association between PFC dysfunction and impulse subtype
of aggressive behaviour
PFC study
APD group – lower grey matter volume in the PFC; White matter – not affected
Fear inhibition
• Impaired fear response – don’t feel fear as normal people à increased likelihood to
engage in criminal behaviour
Heart rate – APD did not show an increase in their heart rate
APD also did not show skin conductance, i.e.: sweating
• 5min to prepare a speech about “your flaws as a human being”
Age-Crime curve
Most of us fall into the adolescence limited anti-social behaviour
Limbic system
• Primary instinct part of the brain
Amygdala
• Emotions
• How we process emotional stimuli
• Overstimulation of the amygdala à violent, aggressive behaviour
, • Lesions of the amygdala à flat affect, not many peaks/lows in emotions, emotional
stimuli do not “stick” à could lead to violence
prefrontal dysfunction is associated with aggressive and/or violent behavioural histories
• lower prefrontal activity, decreased grey matter volume
• evidence is strongest for an association between prefrontal dysfunction and an
impulsive subtype of aggressive behaviour
temporal lobe dysfunction, particularly left-sided medial-temporal (subcortical) activity, is
associated with aggression and/or violence
the relative balance of activity between the prefrontal cortex and the subcortical structures is
associated with impulsive aggression and/or violence
• reduced prefrontal functioning relative to subcortical functioning was characteristic of
those who commit impulsive acts of aggression and/or violence
• by contrast, aggression and/or violence of a predatory nature was not related to reduced
prefrontal and/or subcortical ratios.
traumatic brain injuries precede violence and law-enforcements contact
• could be because of abuse (risk factor)
