forensics Flashcards
the top down approach
A tool to help investigators to accurately predict likely offenders.
american approach
US- result of work by FBI in 1970s
drew upon data from in-depth interview
categorised into organised or disorganised
data from crime scenes match they can predict patterns
this could be used to find the offender
collect data about a murder characteristics of the murderer the crime scene and then decide on the category the data best fit
organised and disorganised type of offender
Organised offender- Evidence of planning, targets victim, tends to be socially and sexually competent with higher-than-average intelligence.
Disorganised offender- Little evidence of planning, leaves clues, tends to be socially and sexually incompetent with lower-than-average intelligence.
constructing an FBI profile
(1) Data assimilation- profiler reviews evidence
(2) crime scene classification- organised or disorganised
(3) crime reconstruction- hypotheses of events and behaviour of the victim
(4) profile generation- hypotheses related to the likely offender
research support
strength- support for a distinct organised category of offender
100 US murders each committed by a different serial killer
technique called smallest space analysis
this analysis revealed that there does seem to be a subset of features of many serial killings which matched the FBI typology for organised offenders.
suggest that a key component of the FBI typology approach has some validity
counterpoint
many studies suggest that the organised and disorganised types are not mutually exclusive.
difficult to classify killers as one or the other type
a killer may have multiple contrasting characteristics such as high intelligence and sexual competence but commit a spontaneous murder leaving the victim’s body at the crime scene
suggesting that the organised disorganised typology is probably more of a continuum.
wider application
strength- adapted to other kinds of crimes eg burglary
critics claim that it only applies to a limited number of crimes eg sexually motivated murder
reports that top down profiling has recently been applied to burglary leading to an 85% rise in solved cases in three US states.
add in two other categories- interpersonal- know the victim and steal something of significance and opportunistic- inexperienced younger offenders
suggest that top-down profiling has wider application than was originally assumed
flawed evidence
limitation- evidence that it is based on
FBI profiling was developed using interviews with 36 murderers in the US
25 were serial killers
other 11 being single or double murderer
24- organised
12- disorganised
sample is poor- FBI didn’t select a random or even a large sample and didn’t include different kinds of offender
no standard questions and not comparable
doesn’t have a sound scientific basis
personality
limitation- based on behaviour consistency may not always lead to successful identification of an offenders
based on behaviour consistency-
serial offenders have characteristic ways of working
referred as leaving their signature on the victim
level of violence or souvenir
questions the idea of behavioural consistency- personality drives behaviour
behaviour is driven more by situation than personality
eg people are not aggressive but in certain situations
behavioural patterns tell us little about the behaviour in everyday life
profiling method based on behavioural consistency may not always lead to successful identification of an offender.
bottom up approach
Profilers work up from evidence collected from the crime scene to develop hypotheses.
british
instead the profile is data driven and emerges as the investigator engages in deeper and more rigorous scrutiny of the details of the offence
more grounded in psycho
investigative psychology
Establishes patterns of behaviour forming a statistical ‘database’.
Interpersonal coherence- Offender’s behaviour at crime scene reflects their everyday behaviour and thus is a clue.
Forensic awareness- Individuals who have been the subject of police interrogation before ‘cover their tracks’.
geographical profiling
The location of crimes is a clue, crime mapping based on psychological theories of offender’s behaviour in relation to their home base.
Canter’s circle theory- Marauders operate close to home, commuters operate further afield.
spatial decision- important insight into the nature of the offence eg planned or opportunistic
revealing other important factors about offenders
evidence for investigative psychology
strength- evidence supports its use
66 sexual assault cases
data was examined using smallest space analysis
several behaviours were identified as common in different samples eg impersonal language
each individual displayed a characteristic pattern of such behaviour and help establish whether two or more offences were committed by the same person
supports basic principle of investigative psychology that people are consistent in their behaviour
counterpoint
case linkage depends on the database and this will only consist of historical crimes that have been solved.
the fact that they were solved may be because it was relatively straightforward to link these crimes together in the first place
suggesting that investigative psychology may tell us little about crimes that have few links between them and therefore remain unsolved
evidence for geo profiling
strength- evidence to support
120 murder cases involving serial killers
smallest space analysis reveals spatial consistency in the behaviour of the killers.
the offender base was invariably located in the centre of the pattern. the effect was more noticeable for offenders who travelled short distances
supports the view that geo info can be used to identity an offender
geo info insufficient
limitation- may not be sufficient on its own
the success of geo profiling msy be reliant on the quality of data that the police can provide
recording of crime is not always accurate can vary between police forces and estimated 75% of crime are not even reported to police in the first place.
calls into question of utility of an approach that relies on the accuracy of geo data
other factors are just as important for creating a profile eg timing, age, experience
geo info alone may not always lead to the successful capture of an offender
mixed result
limitation- little practical value
mixed history
regarded different ways by police forces
some positive- 48 police departments found advice useful in 83% of cases
some negative- 3% cases lead to accurate identification of the offender
colin stagg case
chemistry students produced more accurate offenders profiles on solved murder cases than experienced senior detectives
little practical value
may focus police investigations
new lines of enquiry
but leads to identification of the offender falls short
eysenck’s theory
Three dimensions combine to form personality: introversion–extraversion (E), neuroticism–stability (N), psychoticism–sociability (P).
bio basis
bio origin
types of nervous we inherit
innate bio
extravert- underactive nervous system
seek excitment stimulation more likely to engage i risk taking behaviour
neurotic- high levels of reactivity in the sympathetic nervous system, quick to respond- nervous jumpy general instability= difficult to predict
psychotic- higher levels of testosterone unemotional and prone to aggression
criminal personality
Mostly neurotic-extraverts: emotionally unstable and overreact (neuroticism) + need arousal and enjoy danger/risk (extraversion). Also high P (aggressive, lack empathy).