forensics Flashcards
what are the 2 approaches to offender profiling
- top down
- bottom up
what is the top down approach also known as + who was it developed by
- american approach
- developed by fbi
how was the top down approach developed
- through interviews with 36 serial killers
- behavioural science unit drew upon data gathered from in-depth interviews with 36 sexually motivated serial killers
- match what is known about the crime and offender to a pre-existing template developed by the fbi
- offenders classified into 1 out of 2 categories based on evidence
what categories can offenders be classified into
organised offender
disorganised offender
organised offender profiling
- tend to plan crime
- meticulous at covering tracks
- leave little to no clues
- victim likely to be a stranger
- socially and sexually competent
- married/co-habiting
disorganised offender profiling
- unplanned/haphazard
- likely to leave clues
- likely to have known the victim
- socially and sexually inadequate
- unskilled occupation
- sexual problems in relation to mother
- lives alone
constructing a fbi profile
- data assimilation review of evidence
- crime scene classification, organised or disorganised
- crime reconstruction, hypothesis in terms of sequence of events
- profile generation - demographic, background, physical characteristics
example of when top down approach was used to catch an offender
holmes & holmes 1996:
- murder of young girl and her boyfriend-
- suspect showed photographs of crime scene and he showed familiarity with the crime: gave himself away
evaluation of top down approach
original sample used to develop profile are not representative of all criminals:
- initial category = 36 killers: 25 serial killers, 11 double or single killers therefore not representative
- based on self reports: may be exaggerated; respondents may be too embarrassed to reveal private details; various biases may affect the results, like social desirability bias
only applies to particular crimes such as serial killers:
- method better suited to certain crimes e.g rape, murder etc (male predominant crimes): causes a gender bias in the approach
- crimes such as burglary don’t lend themselves to profiling as you cannot retrieve much information about the offender from the crime scene
based on outdated models of personality - assumes characters are stable and more modern approaches look at situations changing personality
- crime classifications = too simple
- further research shows that there are 4 types of killers according to Holmes visionary, mission-oriented, hedonistic, and power or control
evidence doesn’t support the disorganised offender - Canter’s research only supports organised
- undermines profile
- canter used a technique called smallest space analysis - analysed data from 100 murders in the USA
- findings suggested a distinct organised type but no disorganised
bottom up approach
- profilers work up from evidence collected at the crime scene
- makes use of past data on similar crimes committed in order to build a picture of the offender
techniques used in bottom up approach
- investigative psychology
- geographical profiling
- forensic awareness
investigative psychology through interpersonal coherence
- investigative psychology = applying statistical procedures alongside psychological theories to the analysis of crime scene evidence
- interpersonal coherence = offender’s behaviour towards victims and during crimes reflects their normal behaviour
geographical profiling
- takes note of the principle of time and place
- canter and young’s (2008) study identified number of clues regarding place of crimes in relation to offender
canter’s circle theory
- marauders
- commuters
- the pattern of offending is likely to form a circle around their usual residence.
- such spatial decision making can offer the investigative team important insight into the nature of the offence -whether the crime was planned or opportunistic, mode of transport, employment status.
marauders
- commits crimes close to where they live
- more familiar with the area and may feel secure there
commuters
- commit crimes away from where they live
forensic awareness
- knowledge of how police investigate the crime would suggest the offender previously has been questioned/arrested
- behaviour may denote how mindful they are at covering their tracks
example of when bottom up approach has been used
- john duffy case: railway rapist
- 23 assaults over 4 years
- canter used geographic profiling to study the location of the crimes going back over 4 years.
- helped pin down where the attacker lived.
- pattern discovered suggested the killer was a marauder who operated out of a home base.
- profile Canter created said he was married with no children and had marriage problems; he was physically small with feelings of unattractiveness and lived in Kilburn or Cricklewood.
- this offender profiling was found to be accurate as Duffy lived in Kilburn, was married, infertile and separated from his wife, was 5’4” and had acne.
evaluation of bottom up approach
evidence supports investigative psychology - canter 1990:
- conducted a content analysis of 66 sexual assault cases
- data examined using smallest space analysis
- several characteristics identified as common e.g use of impersonal language
evidence supports geographical profiling:
- lundrigran and canter collated info from 120 murder cases
- smallest space analysis revealed spatial consistency in behaviour of killers
- location of each body disposal site was in a different direction from previous sites
- created a ‘centre of gravity’
scientific basis:
- research supporting the bottom up approach is more scientific than the top down approach which is more based in speculation and hunches
wider application:
- bottom up approach can be applied to more types of crime than the top down approach
- techniques like small space analysis and the principle of spatial consistency can be used in investigation of crimes like robbery and serious crimes e.g murder
case of when profiling went wrong
- case of rachel nickell
- rachel was murdered and criminal profiler paul britton assigned to help case
- drew up offender profile
- colin stagg quickly targeted as he fit profile but after 5 months of an undercover police woman pursuing him trying to get him to confess, the judge threw the case out
- in 2008, robert napper was convicted
- but he wasn’t considered a suspect because he was a few inches taller than the profile
