forensic psychology

• Top-down approach summary 


  Originated in the FBI, a qualitative approach to offender profiling based on past experiences and intuition rather than scientific methods
• 4 steps of top-down approach

  1. Crime classification

  2. Crime reconstruction

  3. Profile generation

  4. Data assimilation
• Organised offender


  • Crime is planned, victim is specifically targeted, weapon absent, clues hidden, socially/sexually competent, potentially living with family and having good job and car
• Disorganised offender


  • Crime is not planned, victim randomly chosen, weapon present at crime scene, clues left, lonely and not sexually/socially competent
• The FBI interviewed 36 convicted individuals and categorised them into two groups: organised and disorganised
• One limitation of the top-down approach is that it has limited explanatory power as it can only be used to explain crimes where there are obvious, visible characteristics
• The top-down approach may only be effective with blue collar crimes and lacks generalisability to all crimes, such as middle class crimes like fraud where there is no crime scene or physical evidence to analyse
• Limitation of too down approach

  • It can be considered unscientific as the method relies more on intuition than fact and evidence
  • It can be seen as unreliable and not following the scientific requirements of psychology, potentially leading to false convictions of individuals
• limitation however

  • Increases number of successful convictions made, protecting future individuals from harm, and making the streets safer overall
  • Decreases cost of additional policing as there is less wanted criminals
• Evidence on organised and disorganised offender types


  • There is evidence to support the existence of an organised offender type
  • The same cannot be said for disorganised type (canter et al)
  • Researchers analysed data from 100 murders in the US, with comparisons of each made to 39 typical traits of both offender types
  • The disorganised offender cannot be identified as distinctly different from organised offenders suggesting system lacks validity and breadth
  • Only US crimes analysed, differs for all cultures
• Bottom-up approach to offender profiling

  1. Investigative psychology undertaken in the UK

  2. Relies on making inferences from actual data

  3. Develops a profile as the crime scene and eyewitness testimonies are analysed
• Bottom-up approach


  • More scientific as the method relies on making inferences from actual data
  • Two hallmarks: investigative psychology and geographical profiling
• Investigative psychology


  Uses computer databases and statistical procedures to look for similarities and differences in patterns between offences and offenders
• Key factors investigated in investigative psychology

  • Interpersonal coherence (way offender behaves at crime scene/how they interacted with victim)
  • Significance of time and place (may indicate where offender is living if crime takes place within same 'centre of gravity')
  • Forensic awareness (focuses on those who have been the focus of police attention before, behaviour may show how mindful they are of covering their tracks)
• Geographical profiling

  Offenders' operationalised base, or their homes is revealed by the geographical location of their crime-crime mapping
• Geographical profiling


  1. Involved the circle theory

  2. Canter and Larkin proposes people operate within imagined boundaries which crime are likely to be committed

  3. Proposed 2 models of offenders: the marauder (offender operates near home base) and the commuters (offender likely travelled long distance from home)

  4. Offender pattern most likely form a circle around their home and give investigators idea of residence
• limitation of bottom up approach 


  • Useful method but does not always lead to the correct identification of the offender
  • Information from an offender profile only led to the successful identification of the offender in 3% of cases but was useful 83% of the time
  • Best reserved for simply narrowing the field of enquiry, as opposed to being relied upon as a chief means of offender identification
• Offender profiling overall may be considered unreliable as the Rachel nickel murder case highlighted how a profile can fit more than one person and be misused
• Collin Stagg was charged with murder because he matched the profile despite no forensic evidence and was later found to be innocent-highlighting how it may be unreliable
• The offender profile used to intensify and arrest john Duffy was highly successful, made Duffy seem like a much more likely suspect than previously thought