forensic psychology

Criminal Psychology

The application of psychological theories and research to understand crime, improve police investigations, analyse courtroom behaviour, and support rehabilitation.

Offender Profiling

An investigative tool that uses psychological theory and crime scene evidence to predict the likely characteristics, behaviour, and habits of an unknown offender.

Purpose of Profiling

To predict who the offender might be, who they may target next, where and when they might strike, and how they should be interviewed.

Profiling as an Investigative Tool

Profiling supports police investigations but should not be used alone or as definitive proof.

Types of Evidence in Profiling

Includes DNA, CCTV, witness statements, pathology reports, crime scene photos, shoe prints, tyre tracks, and environmental damage.

🕵️ TOP-DOWN VS BOTTOM-UP PROFILING – AO1

Top-Down Profiling (FBI Approach)

A deductive approach that applies pre-existing typologies (organised/disorganised) to a crime scene to classify the offender.

Bottom-Up Profiling (British Approach)

An inductive, data-driven approach that builds a profile from patterns across many crimes using statistics and psychological theory.

🕵️ TOP-DOWN APPROACH – AO1

Top-Down Approach (Ressler, Douglas & Burgess)

An FBI method developed in the 1970s based on interviews with 36 sexually motivated serial killers to create offender typologies.

Organised/Disorganised Typology

A classification system that categorises offenders based on crime scene features and inferred personality traits.

Modus Operandi (MO)

The offender’s method or ‘signature’ way of committing crimes that helps link offences to the same individual.

Stages of FBI Profiling

Data assimilation → crime scene classification → crime reconstruction → profile generation.

🧍 ORGANISED OFFENDER – AO1

Organised Offender

An offender who plans crimes carefully, brings tools, leaves little evidence, targets strangers, and shows high control at the crime scene.

Organised Offender Characteristics

High IQ, socially competent, skilled employment, may follow media coverage and communicate with police.

🧍 DISORGANISED OFFENDER – AO1

Disorganised Offender

An offender whose crimes are impulsive, chaotic, leave lots of evidence, use improvised weapons, and show little control.

Disorganised Offender Characteristics

Lower IQ, socially isolated, unskilled, history of abuse, lives near the crime scene, panics under stress.

🧪 TOP-DOWN APPROACH – AO3

Limitation – Unrepresentative Sample

P: The typology is based on a biased sample.
E: The FBI interviewed only 36 American, male, sexually motivated serial killers.
A: This limits generalisation to other crimes, cultures, and genders.
L: Therefore, the top-down approach has low population validity.

Limitation – Lack of Empirical Support (Canter et al., 2004)

P: The typology lacks scientific support.
E: Canter found evidence for organised offenders but not for disorganised ones.
A: Many offenders show mixed features.
L: Therefore, the classification is overly simplistic and unreliable.

Limitation – Over-Simplification (Godwin, 2002)

P: Real offenders rarely fit neatly into categories.
E: Godwin argued most offenders display both organised and disorganised traits.
A: This reduces practical usefulness.
L: Therefore, the model lacks validity.

Research Evidence – Snook et al. (2007)

P: Profiling has limited predictive accuracy.
E: Meta-analysis showed profilers were no better than non-profilers.
A: This suggests profiling relies on common sense rather than science.
L: Therefore, top-down profiling has low predictive validity.

📊 BOTTOM-UP PROFILING / INVESTIGATIVE PSYCHOLOGY – AO1

Investigative Psychology (Canter)

A bottom-up approach that uses psychological theory and statistical analysis to interpret crime scene behaviour.

Smallest Space Analysis (SSA)

A statistical technique that maps how often behaviours occur together across crimes to identify patterns and link offences.

Interpersonal Coherence

The idea that how an offender treats victims reflects how they behave in everyday life.

Geographical Profiling

A technique that uses crime locations to predict the offender’s home base or operational area.

Circle Theory (Canter & Larkin, 1993)

The idea that most offenders live within a circle drawn around their crime locations.

Marauder

An offender who lives inside their offending area.

Commuter

An offender who travels into the area to commit crimes.

📍 BOTTOM-UP – AO3

Research Support – Canter & Lundrigan (2001)

P: There is strong support for geographical profiling.
E: Found killers’ homes were often at the centre of body disposal sites.
A: This supports spatial consistency.
L: Therefore, bottom-up profiling has good empirical validity.

Research Support – Snook et al. (2005)

P: Real-world evidence supports crime mapping.
E: 63% of killers lived within 6 miles of the crime scene.
A: This shows geographical profiling is useful.
L: Therefore, the approach has practical value.

Limitation – Data Quality

P: Profiles are only as good as the data.
E: Many crimes go unreported and records vary between police forces (Ainsworth, 2001).
A: This reduces accuracy.
L: Therefore, bottom-up profiling is limited by input quality.

Strength – Scientific Basis

P: Bottom-up profiling is more scientific than top-down.
E: It uses statistics, databases, and psychological theory.
A: This improves objectivity.
L: Therefore, it has higher scientific credibility.

🧬 LOMBROSO & THE ATAVISTIC FORM – AO1

Atavistic Form

The idea that criminals are evolutionary throwbacks with primitive physical characteristics.

Lombroso’s Theory

The view that criminals are ‘born not made’ and can be identified by physical features.

Examples of Atavistic Traits

Sloping brow, strong jaw, facial asymmetry, extra digits, tattoos, dark skin, unemployment.

🧬 LOMBROSO – AO3

Strength – Historical Importance

P: Lombroso was the first to study crime scientifically.
E: Before him, crime was seen as moral or religious failing.
A: He laid foundations for modern profiling.
L: Therefore, his work has historical value.

Limitation – Goring (1913)

P: Lombroso’s findings lack validity.
E: Goring found no physical differences between criminals and non-criminals.
A: This suggests Lombroso’s conclusions were biased.
L: Therefore, the theory lacks scientific credibility.

Limitation – Methodological & Ethical Issues

P: Lombroso used biased, uncontrolled methods.
E: No proper control group and heavy confirmation bias.
A: Also labels people as criminals based on appearance.
L: Therefore, the theory is unscientific and socially sensitive.

Limitation – Self-Fulfilling Prophecy (Agnew, 1992)

P: Labelling may cause crime rather than predict it.
E: People treated as criminals may behave criminally.
A: This suggests social factors matter more than biology.
L: Therefore, Lombroso’s theory is overly deterministic.

🧬 GENETIC EXPLANATIONS OF CRIME – AO1

Genetic Explanation

The view that some individuals inherit traits that predispose them to offending behaviour.

Diathesis–Stress Model

The idea that genetic vulnerability interacts with environmental stress to produce crime.

Twin Studies

Compare MZ and DZ twins to assess genetic influence.

Adoption Studies

Compare biological and adoptive parents to separate genes and environment.

🧬 GENETICS – AO3 EVIDENCE

Christiansen (1977)

MZ concordance 35% vs DZ 13% → genetic influence.

Crowe (1972)

Criminal biological mother → 50% criminal by 18 vs 5% control.

Mednick et al. (1984)

Both genes and environment contribute → supports diathesis–stress.

Brunner et al. (1993)

Defective MAOA gene linked to violent behaviour (Brunner syndrome).

Tihonen et al. (2015)

MAOA and CDH13 linked to violent crime in Finland.

🧠 NEURAL EXPLANATIONS – AO1

Neural Explanation

The view that crime is linked to brain structure or neurotransmitter imbalance.

Serotonin

Low levels linked to impulsivity and aggression.

Dopamine

High levels linked to risk-taking and reward-seeking.

Prefrontal Cortex

Controls decision-making and impulse control.

Amygdala

Regulates emotional responses and aggression.

🧠 NEURAL – AO3

Raine et al. (1997)

P: Found brain differences in violent offenders.
E: Reduced activity in prefrontal cortex and other areas.
A: Suggests biological basis.
L: But cannot show cause and effect.

Limitation – Determinism

P: Biological explanations may remove responsibility.
E: But biology does not mean inevitability.
A: Environment still matters.
L: Therefore, interactionist approach is better.