Forensic Psychology


Defining Crime

Crime is a social construct relative to the morals and norms of a current society. There are several problems in defining crime:

  • Age: age of criminal responsibility varies across time and culture
  • Culture: social norms of crime vary
  • Historical context: even within a ulture, law is being constantly updated
  • Circumstance: for a crime to be persecuted a person must be shown to have commited the act and also intended for it to be commited
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Measuring Crime

Official Statistics:

Data is gathered from several sources by the Office of National Statistics on the amount of crime commited in england and wales. Published every year headlining amount and types of crime commited 

Police recording of crime:

Data is taken from police computer systems that log reports of crime and therefore measures amaount of crime commited, stats given to office of national statistics

Victim surveys

The Crime Survey for england and wales conducts annual face to face surveys with 40,000 people about criminal experince (provides data on 'dark figure of crime'.

Offender Surveys

Annual survey of 5000 people on commitance of crime (high reponse rate but varied reliability)

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Offender Profiling: top-down

  • Profiling inputs- the crime scene (photos, drawings), info about victim (employment, hobby, relationships) and the crime (weapon, cause of death, autopsy report). To avoid bias no suspects are considered at this stage.
  • Decision-making model- profile organises data into meaningful patterns (murder type: mass, spree or serial; time factors: time taken, time of day; and location)
  • Crime assessment- organised and disorganised crime
  • Criminal profile- profiler hypothesises about offenders background
  • Crime assessment- police are given written report and persons matching profile are evaluated
  • Apprehension- if a suspect is apprehended, entire profile is reviewed
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Top Down research

+ Shawcross: murder 2x children sentenced to 25 years and released after 15. 1 year later he killed 11 prostitutes. McCray (FBI) made an accurate profile which lead to arrest as he theorised Shawcross would return to teh body.

- Snook: "effective as a psychic"- Barnum effect suggests that due to high ambiguity of profilers suggestions they could fit almost any situation. Could lead to misleading information in court.

- Jackson: suggests that smart offenders can read about how profiles are constructed and deliberately  mislead profilers by providing misleading clues. Question of whether profiling methods should be released to public.

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Oragnised and Disorganised Typologies


  • orderly life (attacks after a critical event)
  • planning and control evident in crime 
  • average or high intelligence 
  • socially competent 
  • probably eldest child in family

Disorganised :

  • crime of passion 
  • no evidence of pre-planning 
  • below average intelligence 
  • not socially competent 
  • poor employment history 
  • low birth order
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Offender Profiling: bottom-up

Makes no assumptions about crikminal until data from the crime scene has been taken from a data base of past crimes.

Investigative psychology:

  • Forensic awareness (no evidence left =maybe criminal record)
  • Time and Place: lifestyle of criminal
  • criminal career
  • interpersonal coherance: behaviour in crime same as behaviour IRL
  • criminal charcteristics: categorising offedners 

Geographical Profiling:

Developed by Canter, analyses time and place the crime was commited in (geographical pattern of crime). Commuter (travels to crime scene) or marauder (commited on own territory)- circle theory. 

Criminal Geographical Targeting (CGT): a computerised system based on Rossmo's formula presenting a 3D map of spatial data relating to time, distance and movement to and from crime scenes. This 'jeopardy surface' uses different colours to indicate likely closeness of offenders residence to crime scene.

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Bottom-up research

Canter led a profile on John Duffy that eventually led to his arrest. He used theories of: Interpersonal coherence ( from canters assumption that Duffy would keep to him self due to him using minimal dominance in his attacks as he attacked weak victims).

He could also have determined where he lived and worked by Duffy's knowledge of trains (career) and the occupation of the rapes/murders (around his home area - marauder) Canter gave a total of 17 characteristics he determined through profiling and 12 were correct in the end. 

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Atavistic (historical) explanation.

Atavistic form: a historical approach that uses a biological basis to explain why we become criminals. Uses idea that criminality is a throwback to primate form. Turvey identified 18 characteristcis such as: assymetical face, excessive jaw, unusual ears and excseeive arm length.

Lombroso et al: 50,000 live/ post mortem exams measuring skulls. In 383 criminals, 21% had 1 atavistic trait, 43% has 5 traitsLombroso later proposed inherited atavistic forms interacted with a person's physical and social environment to determine behaviour.

Kretchmer's study of over 4000 criminals led him to propose 4 main body types and associated criminal behaviour: Leptosome- tall and thin; petty thieves, Athletic - tall and muscular; violent crime, Pyknic- short and fat; deceptive crime, Dysplastic- ramge of types; moral crime.

- Lombroso did not screen for people w learnign disabilities so not reliable 

- extreme reductionism 

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Genetic Explanation

Twin studies

Raine: MZ concordance= 52%, DZ concordance =21% for criminality

MAOA gene theory: Brunner

DNA analysis of an italian family with mant convictions for sexual or violent crimes. Shared the absence of  a gene that led to a decrease in seretonin breakdown = increased aggresion. Similar resualts from Tihonen in study of 900 offenders that had low levels of MAOA and no activity f the CDH13 gene. Estimated that 5-10% crime in Finland could be due to these factors.

Genetic influences on aggression:

Somep psychologists believe that aggression can lead to offending. Studies have shown a link between genes and levels of aggresion, particularly through the use of twin studies.

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Neural Explanation

Neurochemical Differences:

  • Noradreneline: fight or flight, increased levels may increse aggression 
  • Seretonin: mood and impulse control, incresed levels lead to poor impulse controll
  • Dopamine: released when we do something pleasurable, for some this is aggression

+ Brunner et al: case study of a family of violent cirminals that showed differences in the way seretonin was metabolised.

Structural Differences:

  • The limbic system: A smaller than average amygdyla has been linked to psychopathy which may lead to an inceased dispoition fior criminality (lack of guild or empathy).
  • The anterior cingulate cortext: liks limbic to preforontal cortex (impulse controll). Damage to this area has been linked to criminal behaviour.

- impossoble for this to prove causality

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Eysencks theory of the criminal personality

Psychotocism - High levels of testosterone linked to increased aggresion (more likely to commit crime; high aggression and lack of conscience)

Extraversion - ascending reticular activating system (ARAS) is responsible for the general arousal level in the NS. If level of activation is low, extraverts seek stimuli to increase arousal (thrill seeking could lead to criminal activity)

Neurotocism - The limbicsystem (control emtional reactions) is easily triggered. Neurotic people reacr to emotional stimuli quickly

Eysenck and Eysenck compared 2070 male prisoners' scores on PEN with 2422 male controls. Groups divided into age groups 16-69. on measures of PEN across all age groups, prisoners recorded higher scores than controls which supports original theory.

Digman suggests alongside E and N there are additional dimensions of openness, agreeableness and conscientiousness. Multiple combinations of these are availible so a high E and N score doesn't mean that offending is inevitable.

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Cognitive explanation

Piaget: cog ability develops over time so childrent think differently to adults (impact ability to tell right from wrong). Stage 1: focus on rules Stage 2: responsobility Stage 3: justice (by age 9)

Kohlburg suggested this model was too simplistic. He furthered this theory by using moral dilema research (crime or not if for a cancer patient etc)

Level 1: Pre-conventional morality (right or wrong depends on the outcome of the behvaiour

  • stage 1: acts are right or wrong depending on punishment or reward
  • stage 2: multiple views about right or wrong are recognised

Level 2: Conventional Morlality (morality internalised from others and society)

  • stage 3: gain approval from following rules
  • stage 4: maintain order in society by obeying rules

Level 3: Post-conventional Morality

  • stage 5: distinguish between morality and legality (can break rules for morality)
  • stage 6: conciounce defines right and wrong (higher ethical rules of the universe apply)
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