Forensics Flashcards
What is offender profiling?
A method of identifying the perpetrator of a crime based on analysis of the nature of the offence and the manner in which it was committed.
What is an offender profile?
Outlines the type of person likely to have committed a crime.
They are used to shorten the list of suspects.
What is a dichotomy?
Two exclusive categories; organised or disorganised.
What are the organised characteristics of a crime?
- Actions reflect planning and control
- Uses weapons and restraints that are planned
- Crime scene is in order, leaves few clues
- Victim is a targeted stranger
What are the likely characteristics of the offender in an organised crime?
- In a skilled occupation
- Above average intelligence
- Married/co-habiting
- Socially and sexually competent
What are the disorganised characteristics of a crime?
- No pre-planning
- Uses whatever weapons are available
- Crime scene is chaotic, leaves blood, fingerprints and murder weapon behind - little attempt to hide evidence
- Victim is random (convient)
What are the likely characteristics of an offender in a disorganised crime?
- Unskilled occupation
- Low levels of intelligence
- Lives alone - near crime scene
- Sexually and socially inadequate
What are the four stages in the construction of a top down profile?
1 - Data assimilation (profiler reviews evidence; crime scene, witness reports)
2 - Crime scene classification (either organised or disorganised)
3 - Crime reconstruction (hypothesis in terms of sequence of events)
4 - Profile generation (hypothesis related to the likely offender)
What are the limitations to top down profiling?
- The original sample is based on interviews 36 sexually motivated killers; small sample.
- Only applies to particular crimes such as serial crimes.
- Based on outdated models of personality.
- Classification is too simplistic; killers can be act-focused or process-focused, so there may be more categories.
- Evidence does not support the dichotomy - Canter analysed 100 cases of serial killings and found that most crime scenes include elements of both organised and disorganised.
What hypothesis did Canter develop?
- Criminal consistency hypothesis
- States that an offender’s behaviour while committing a crime will be consistent with their behaviour in their everyday life.
- Contains Interpersonal consistency and Spatial consistency
What is interpersonal consistency?
The theory that the behaviour of the offender at the time of the crime will be similar to everyday life.
For example, ‘overkill’ indicates a perpetrator of a violent, sexual crime is likely to be on record for domestic violence.
What is spatial consistency?
Locates the most probable location of the home of the offender from the distribution of the scenes of the crime.
It assumes criminal offences will occur in places the offender makes regular use of.
What is distance decay?
The further from the home of the offender, the fewer crimes.
What is circle hypothesis?
The majority of offender’s homes can be located within a circle, with its diameter defined by the distance between the offender’s two furthermost crimes.
What is the Marauder model?
The offender operates in close proximity to their home base.
What is the commuter model?
The offender travels from home base to a location, eg. workplace, partner’s home, and operates in a circle pattern there.
What is dragnet?
A computer package, based on Canter’s empirical research into the spatial behaviour of offenders.
It uses a series of crime locations and determines the most likely area for the perpetrator’s home.
Who is John Duffy?
- The ‘Railway Rapist’
- 24 sexual attacks and 3 murders in the 1980s, around railway stations across North London.
What from Canter’s profile turned out to be correct about John Duffy?
- Canter suggested he lived in an area near to the area of his first crimes; Duffy did live in the area he suggested.
- Canter said he had a knowledge of railways; Duffy worked for British Rail.
- Canter said he had previous criminal record for violence; Duffy raped his wife at knifepoint.
What are the strengths of Bottom-Up Offender Profiling?
- Case of John Duffy supports the method; led to the capture of Duffy.
- Evidence supports geographical profiling as effective: analysis of 120 serial murder cases was conducted and found evidence for spatial consistency in the behaviour of the killers. The offender’s base was inevitably located in the centre of the circle created by their crimes. However, this is only really useful for serial crimes.
What is an atavistic form?
Proposed criminals are a sub-species of genetic throwbacks that cannot conform to the rules of modern society.
Distinguishable by particular facial and cranial characteristics.
What did Lombroso investigate?
The facial and cranial characteristics of over 4,000 Italian convicts both living (90%) and dead (10%). Measurements were taken of the skulls and features of criminals; this is empirical evidence. 'Markers' - Facial asymetry - Narrow, sloping forehead - Strong, prominent jaw - High cheekbones - Dark skin - Extra toes, nipples or fingers
What did Lombroso conclude?
That criminals are genetic throwbacks with identifiable atavistic features and that specific features are associated with specific crimes:
- Bloodshot eyes/ curly hair/ long ears: murderers
- Glinting eyes/ fleshy lips/ projecting ears: sexual deviants
- Thin lips: fraudsters
What is the strength of the theory of the atavistic form?
- The contribution to criminology: it paved the way for empirical examination of criminals, and also for offender profiling.
What are the limitations of the theory of the atavistic form?
- It can be accused of scientfic racism because some features that they identified as linked with criminality were more common in people of African descent.
- There is contradictory evidence: Goring conducted a comparison between 3000 criminals and 3000 non-criminals and concluded there was no evidence that offenders are a distinct group with unusual features.
- There are confounding variables: physical injuries to head and disease in childhood can cause the physical differences.
How is MAOA a genetic explanation for offending?
MAOA is an enzyme that breaks down neurotransmitters such as serotonin at the synapses of the brain. Some people have a variant of the MAOA gene which code for this enzyme. The variant means they produce less of the enzyme which means they end up with more serotonin left to be active in the synapses. This variant is associated with offending. This results in losing sensitivity to serotonin so that it no longer functions as it should in the brain.
What happened in Tiihonen’s study?
- Almost 900 offenders underwent genetic analysis.
- Cadherin 13 (CDH13) variation - codes for protein involved in neuron growth; linked to ADHD and substance abuse
- Participants with both MAOA and CDH13 variations were 13 times more likely to have a history of violence.
- This shows there is a genetic basis to offending and that offending is determined by interaction between two or more genes.
What are the strengths of genetic explanations for offending behaviour?
There is evidence to support it from Christiansen’s study, Mednick’s study and Caspi’s study.
What happened in Christiansen’s study?
- Compared concordance rates for having served time in prison.
- 87 MZ twins and 147 DZ twins
- Concordance: 33% MZ and 12% DZ
- Therefore this suggests a strong genetic influence on offending because the higher the percentage of shared genes, the higher concordance rate for being in prison
- However, because concordance rate is not 100% for MZ, the findings show that the environment must also play an important role
What happened in Mednick et al’s study?
- 13,000 Danish adoptees
- No parents with criminal conviction: 13.5% offending rate
- Adoptive parent with criminal conviction: 14.7%
- Biological parents with cc: 20%
- Biological and adoptive parent with cc: 24.5% offending rate
What does Mednick et al’s study show?
- Suggests an interactionist explanation if the effect is even stronger where the biological and adoptive parents have a conviction.
- But there are confounding variables:
- Some children are raised for years by biological parents before adoption
- The prenatal environment impacts the child
- Others maintain contact after separation
What happened in Caspi et al’s study?
- Studied over 1000 participants from childhood to adulthood.
- They carried out genetic analysis and gathered information from participants.
- They found the MAOA variant on its own was not associated with antisocial behaviour. Maltreatment in childhood alone was.
- 85% of males with low MAOA activity and who had been severely maltreated in childhood developed some form of antisocial behaviour.
- An interaction between the variables was shown.
What are the neural explanations of offending behaviour?
Brain structure/pathology
Brain function
Neurotransmitters
How is brain damage an explanation of offending behaviour?
- 8.5% of Americans have had a brain injury
- 60% of the prison population have had a brain injury
- Example of nurture affecting nature
- Brain damage can change structure and functioning