forensics Flashcards
what did Canon and Heritage find from analysis of sex offenders
analysed 66 cases of sexual assault against women by 27 different offenders
rape- where offender doesnt initiate high level of contact they tend to have low sexual contact in life and probably live alone
use of impersonal and degrading language- consider women as objects of desire, have failed relationships with women both domestically and in work
offenders warn victim not to go to the police- usually have knowledge of police procedures/previous offences
offender profiling using the top down approach
the aim is to narrow the list of potential suspects
involves scrutiny of the crime scene
analysis of witness reports
this approach originated with the FBI in america (1970s) using data 36 sexually motivated murderers- inclusing ted bundy and charles manson
the analysis suggested crimes could be divided into organised and disorganised
type of murderer from an organised offender
crime is planned
victim specifically targeted (particular location/charachteristics
body transported from scene of crfrime
high control of situation (use of restraints)
leaves few clues (weapon is usually hidden)
voilent fantasies acted out on victim
likely charachteristics of an organised offender
generally high IQ
socially and sexually competent
confident and attractive
usually living with a partner
car in good working order
follows media coverage of crime
experiencing anger/depression at time of attack and calm after attack
type of murder from a disorganised offender
unplanned/impulsive crime with no plan to avoid detection
random victim
engaged little with victim
facial destruction and sexually sadistic acts performed after death
little attempt to hide evidence at crime scene (body,weapon etc)
what are disorganised offenders usually charachterised by
lives alone, near to crime scene
sexually inadequate
poor social skills
severe forms of mental illness
physically or sexually abused in childhood
confused and distressed at time of attack
how does using the top down approach have the potential to cause harm
profiles based on the top down approach may be based on the barnum effect- ambiguos descriptions can be made to fit any situation eg horoscopes
profiling has the potential to cause harm because profiles may mislead investigations if they are wrong
Jackson and Beckerian suggested smart offenders can read about how profiles are constructed and deliberately mislead profilers by providing misleading clues
what has been argued about the relevance of the top down approach
critics argued the top down approach was only relevant to murder cases however
Meketa reports that 3 states in the US have used it for buglary cases and had an 85% increase in solved cases
in these cases they keep the organised/disorganised distinction but add two more categories: interpersonal (offender knows victim) and opportunistic
suggests the approach has a wider application
the bottom up approach of offender profiling
favoured in the uk where profiles are created in terms of charachteristics, social background and routine behaviour through systematic analysis of evidence at the crime scene and moving UP towards a classification rather than start with a fixed typology the profile is data driven and emerges as the investigator carries out rigorous examination of the details
uses statistical technique to produce predictions about the likely charachterstics of an offender
two examples of the bottom up approach
investigative psychology and geographical profiling
investigative psychology
attempts to apply statistical procedures alongside psychological theory
aim to establish patterns of behaviour across crime scenes
develop a statistical database to act as a baseline for comparison
specific offences then matched against database to reveal details of the offender eg family,background,personal history
aim is to see if a series of offences are linked
what is central to the theory of investigative psychology
interpersonal coherence
forensic awareness
small space analysis
interpersonal coherence
identifying correlations in individuals behaviour between day to day and the crime scene- assumes people are essentially consistent
forensic awareness
behaviours at the crime scene may reveal awareness of police techniques eg Davis 1977- rapist who conceal fingerprints often had a previous conviction for burglary
small space analysis
stats technique developed by Canter
analysed 48 crime scenes for correlations
what are the key things involved in geographical profiling
spatial consistency and crime mapping
circle theory
criminal geographic targeting
spatial consistency and crime mapping
individual activities are confined to a few fairly limited areas so a persons offences will often also be limited to that geographical area=spatial consistency
crime mapping makes inferences about likely home of offender and identifies spatial patterns of behaviour
this is the basis of canters circle theory
circle theory
identifies offender as either Marauder- live in the area crimes are committed or
commuter- travel to an area away from their home eg to work and commit crimes
criminal geographic targetting
computerised system produces a jeapordy surface showing data related to time, distance and movement to and from crime scenes
what offenders support the bottom up approach
the railway rapists
1980s
the railway rapists
24 sexual attacks and 3 murders in North London Canter analysed geographic info and combined with data of past similar attacks and was able to compile a profile of the offender
success in Canters first bottom up profiling case- the railway rapists
helped police reduce suspect pool and led to effective conviction
in surveys of 48 police forces 75% of police said profiling was helpful
however only 3% said it has helped identify the actual offender
evaluation of the bottom up approach- is the distinction between marauders and commuters useful
in a study of 45 sexual assaults (Canter and Larkin) support was found for the distinction between commuters and marauders however 91% were marauders= the majority- so how useful is it to distinguish if most are marauders anyway
Petherick said that if the offenders home isnt at the centre of the geographical circle they may look elsewhere anyway
what is atavistic form
an early biological explanation which proposed criminals are a sub species of genetic throwbacks that cant conform to the rules of modern society
such individuals are distinguished by particular facial and chranial charachteristics- these acted as markers for particular offences
examples of atavistic form
criminals- string prominent jaw high cheekbones
murderers- bloodshot eyes curly hair
sexual deviants- glinting eyes, swollen fleshy lips
fraudsters- thin and reedy lipa
lambrosos research 1876
sysetamtically examined facial and cranial charachteristics of convicts- 3839 alive and 383 dead before concluding there was an atavostic form
these features were considered to be key indivators of criminality
concluded that 40% of crime was committed by those with atavistic form charachteristics
what did lambroso say about environmental influences
inherited atavistic form interacted with a persons physical and social environment- unlikely one factor would be the cause of criminality
environment interacted with atavistic form
how did lambroso later distinguish different types of criminals
lambrosos distinguished between 3 types of criminals
born criminals- atavistic type
insane criminals- suffering from mental illness
criminaloids- a large general class of offenders whose mental charachteristics predisposed them to criminal behaviour under the right circumstances
what are somatotypes
identified 4 main types
Kretschmer studied 4,000criminals
leptosome- tall and thin pretty thieves
athletic- tall and muscular crimes of voilence
pyknic- short and fat- crimes of depression and voilence
dysplastic- more than one type of crime or crimes against morality eg prostiution
why might lambrosos work be accused of scientific racism and linked to the eugenics movement
linked to eugenics movement (Galton 1880s)
influenced by chales darwin and ‘‘survival of the genetically fit’’ theory
he suggested desorable traits are inherited eg intelligence, morality
these groups are at a genetic advantage and breed for good of society- others shouldnt
what contradictory evidence was there against lambrosos research
lambrosos research didnt use controls- cant make a comparison
contradictory evidence-Garing 1913- compared 3,000 convicts qith non convicts-found no difference except that convicts were slightly smaller
what are the two biological explanations of offending behaviour
genetic and neural
genetic explanations of offending behaviour
assume the likelehood of exhibiting criminal behaviour is determined by a persons genetic makeup
what twin studies looked at genetic explanations for offending behaviour
twin studies Raine 1993
research on delinquent behaviour of twins found 52% concordance for MZ twins compared with 21% for DZ
this suggests certain genes predispose individuals to criminal behaviours
what did adoption studies find about genetic explanations for offending behaviour
adoption studies found that adoptees whose biological mothers had a criminal record had a 50% chance of having a criminal record themselves by age 18 whereas adoptees whose biological mothers did not have a criminal record had only a 5% chance of this
what candidate genes are involved in offending behaviour
monoamine oxidase A
MAOA
Cadherin 13 CDH13
diathesis stress
monoamine oxidase A MAOA
Brunner 1993 analysed DNA of a famoly with a history of voilent criminal behaviour and found they shared a gene that casued abnormally low levels of MAOA
deficiency in MAOA has been associated with aggression and voilent crime
Cadherin 13 CDH13
Tihonen 2015
900 offenders
low MAOA
low activity from CDH13 gene
can cause voilent behaviour and crime
diathesis stress
epigentics suggests that gene expression can also be reduced by environmental factors
epigentics- genes can be switched on or off by certain environmental factors such as childhood maltreatment
if the combination of the predisposition (genes) and life experiences (environment) exceeds a threashold the person will start to exhibit offending behaviour
Capsi et al 2002- 12% of men with low MAOA genes had experienced maltreatment when they were babies
issues with twin evidence
limited because of a assumption of equal environments
assumes environmental factors rae consistent because twins are brought up together and therefore must experience similar environments- shared environments assumption -applies more to MZ than DZ twins- MZ look identical so people, especially parents may treat them more similarly
what is a strength of genetic explanations for offending behaviour
lots of research support uincluding research from adoption studies- these studies suggest genes are marginally more significant than environment in influencing offending behaviour
what are the two neural explanations for offending behaviour
brain regions
neurotransmitters
brain region explanations for offending behaviour
an explanation of behaviour (and its disorders) in terms of (dys)functions of the brain and the nervous system including brain structures such as the prefrontal cortex and neurotransmitters such as serotonin and noradrenaline
prefrontal cortex
area involved in regulating emotion and moral behaviour
reduced functioning in this region found in voilent offenders/psychopaths
lowered activity here is associated with impulsive behaviour and loss of control
implicated in planning complex cognitive behaviour personality expression decision making emotional behaviour (higher functioning)
people with antisocial personality disorder have reduced functioning on the prefrontal cortex eg lack of empathy eg Raine
looked at 71 brain imaging studies
murderes psycopaths and voilent individuals showed reduced functioning in PFC
limbic system
series of structures involved in motivation, emotion, learning and memory (amygdala mostly deals with emotion)
studied murderers found not guilty by reason of insanity
abnormal assymetries in limbic system- reduced left amygdala activity- increaszed right amygdala activity
neurotransmitters involved in neural explanations of offending behaviour
seretonin
noradrenaline
mirror neurons
serotonin
mood anxiety happiness
research shows low levels can predispose people to impulsivity and aggression
serotonin inhibits the prefrontal cortex
noradrenaline
arousal and alertness
both very high and very low levels associated with aggression
high levels associated with activation of sympathetic nervous system (fight or flight) can lead to aggression
low levels associated with reduced ability to react/percieve threat
mirror neurons
control empathy
anti social personality disorder sufferers need the empathy switch to be turned on eg told whereas non APD the empathy switch is always on
weaknesses of neural explanations
difficult to infer cause and effect- correlation- Seo et al- do low levels of seretonin cause voilence or does being voilent reduce levels of serotonin
the theory is based on research which usually looks at aggression not offending- do all aggressive people go on to offend- validity
strengths of neural explanations
it allows for many real world applications drugs or surgery to alter these neural changes eg influence diet in prisons
what is a psychological explanation of offending behaviour
personality theory
eysnecks personality theory
eysnecks personality questionaire
suggested that personality can be measured and developed the eysneck personality questionaire a test to measure the extent of extraversion, neuroticism and psychotcism
he related these personality variables to other behaviours such as criminality
eysnecks personality theory
an adults personality is a mix of biological tendencies combined with learning experiences
eysneck proposed that criminals have a specific mix that cause offending behaviour therefore criminality can be explained by specific personality traits
what are the three dimensions that eysneck proposed cause a person to offend
extraversion
neuroticism
psychoticism
extraversion definition
extraverts are charachterised as outgoing, having positive emotions but may get bpred easily, they enjoy risk and danger
what is extraversion biologically determined by
eysneck suggested extraversion is biologically determined by the overall level of arousal in a persons nervous system
extraverts have less innate cortical arousal so seek external stimulation; whereas introverts are innately over aroused so do not seek external arousal
extroversion/introversion
extraverts- under aroused nervous system- need stimulation- less likely to be affected by negative outcomes such as punishment
introverts- over aroused nervous system- avoid stimulation- cannot deal with negative outcomes casually, will take punishment to heart
neuroticism/stability
neurotic- experience more negative emotions- anxiety depression isolation anger easily upset
stable- more posotive emotional states, calm under pressure
neuroticism
based in the sympathetic nervous system, so a tendency to overreact in situations of trheat (fight or flight)
how does neuroticisim link to offending behaviour
instability in the fight or flight response may cause someone to commit a crime because your more likely to interpret ordinary situations as threatening
psychoticism/normality
psychoticism is linked to higher levels of testosterone (could explain why its more prevalent in men)
charachteristics include- egocentric aggressive impulsive lack of empathy and conscience
how does psychoticism link to offending behaviour
higher levels of testosterone can cause someone to commit a crime because testosterone can cause individuals to be more aggressive and a lack of empathy is linked to offending behaviour
aim of mcgurk and mcdougall
to investigate the link between eysencks personality type and criminality
method of mcgurk and mcdougall
100 students classed as delinquents and 100 non delineunts completed EPQ
their scores were calculated
findings of mcgurk and mcdougall
there were significant differences in scores of all 3 dimensions between both groups
the delinquent group had a combination of high P E and N scores