Snook, Canter and Bennell - Bottom-up approach

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  • Created by: Steff06
  • Created on: 30-05-16 14:35
What does Canter's bottom-up approach look for?
Looks for consistencies in offender's behaviour during the crime.
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What are no initial assumptions made about?
No initial assumptions made about the offender and the approach uses computer databases.
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What can be crucial to the success of a case?
The little details that are often overlooked.
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What does geographical profiling involve?
Involves generalising from the locations of linked crimes scenes to the likely home/work/social base of the offender.
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What is the assumption?
That most offenders like to operate in areas they know well.
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What is the crime range of most offenders?
As little as 2 miles.
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What is a distinction drawn between?
Marauders who like to commit crimes in their own neighbourhoods and commuters who travel to commit their crimes.
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What does Canter argue his method is built on?
Psychological theory.
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Describe this psychological theory
People store information about their lives in schemas/mental maps. These are organised knowledge of our experiences.
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Describe each person's mental maps
Each person's mental map is highly individual and the location of crime scenes can be used to infer where the offender is based and other information about their likely interests, employment and relationships.
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What can then be set up?
A surveillance area for the next/subsequent crimes.
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What is one type of geographical profiling?
DRAGNET, which uses information about the location of offences to predict where an offender is likely to live.
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What is a second type of geographical profiling?
Circle theory where circles are drawn around the area of offence to locate the criminal.
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Describe a geographical profile
A prediction of the most likely location at which the search for a serial killer's home should commence.
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What did Canter's laboratory experiment test?
Tested the extent to which human judges could accurately predict the home location of serial offenders before and after training.
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What did they research?
Researched the accuracy with which participants before and after training could predict the likely home of serial offenders and compared these with predictions produced by a geographical profiling system (DRAGNET).
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What groups were in the study?
A control group and an experimental group. Both groups mixed nationality, had no prior knowledge of offender profiling.
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Describe the control group used in this study
21 university students (10 male, 11 female).
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Describe the experimental group
21 students (13 male, 8 female).
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Describe phase 1
All participants given from 10 spatial displays, 1 for each of 10 different US serial murderers, indicating locations of 5 offences committed by a serial murderer.
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What were participants asked to do in all conditions?
Asked to place an X on each spatial display, corresponding to where they thought the offender lived.
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What were the participants asked to explain?
Asked to explain how they came to this conclusion (what heuristics did they use).
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What happened in phase 2?
Spatial displays were taken in.
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What was the procedure for the control group?
Given the same displays again and asked to indicate again where they thought the home location would be. They had no feedback between the 2 phases.
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What was the procedure for the experimental group?
Told the majority of offenders commit offences close to home, the majority of offenders' homes can be located within a circle and the diameter is the distance between the 2 most distant crimes.
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What 2 heuristics were the experimental group given to follow?
Distance decay and circle hypothesis.
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What did the results show about the experimental group?
Showed they made more accurate predictions when they were provided with the 2 heuristics.
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Describe the overall accuracy of the second set of predictions for experimental group
Not significantly different from the accuracy of the predictions generated by DRAGNET.
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Can people be trained to do geographical profiling?
People can be trained to do geographical profiling if given appropriate heuristics.
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What do heuristics seem to do?
Focus the decision making.
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What may there be limited value in?
Limited value in using specially trained geographical profilers or computer programmes.
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Whose home locations is it harder for DRAGNET and the experimental group to predict?
The commuters' home locations.
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Other cards in this set

Card 2


What are no initial assumptions made about?


No initial assumptions made about the offender and the approach uses computer databases.

Card 3


What can be crucial to the success of a case?


Preview of the front of card 3

Card 4


What does geographical profiling involve?


Preview of the front of card 4

Card 5


What is the assumption?


Preview of the front of card 5
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