Bottom Up Approach Flashcards
The bottom up approach is a data driven approach which uses statistical techniques to produce predictions about the likely characteristics of an offender.
Investigative psychology was developed by canter who proposed profiling should be based on psychological theory and research. The three main features are interpersonal coherence, forensic awareness and smallest space analysis. Interpersonal coherence means that people are consistent in their behaviour and that links can be made between elements of the crime and their everyday behaviour. Also peoples behaviour may change over time and so looking at differences in crimes over a period of time may offer further clues
Certain behaviours may reveal an awareness of police techniques or previous experience.
Smallest space analysis is a statistical technique developed by canter. Data about many crime scenes and offender characteristics are correlated so common connections can be identified. Three underlying themes that have been identified are instrumental opportunistic, instrumental cognitive and expressive impulsive.
Geographical profiling also proposed by canter is a form of the bottom up approach which looks at locations of connected crime scenes and considers where the crimes were committed, the spatial relationship between different crime scenes and how they may relate to the offender. Canter and Larkin proposed the idea of two different types of offenders. Marauder- the offenders home is within the area the crime was committed. Commuter- the offender travels to another area and commits the crime
Computerised geographical targeting is a system proposed by rossmo based on his own formula. The formula produces a 3D map displaying spatial data and distance to and from crime scenes. The map is called a jeopardy surface and the different colours indicate likely closeness to crime scenes
One advantage of the bottom up approach is that it is considered to be more scientific than the top down approach because of the use of statistical techniques and computer analysis. However an issue with using such techniques is that the data used to drive these systems is only related to offenders who have been caught and so tells us little about patterns of behaviour related to unsolved crimes.
In terms of computer programming Someone has to develop a formula to use and this may be incorrect which means the data collected will not be valid. This therefore means that the bottom up approach has the potential to be objective and scientific but in practice is biased.
A strength of the bottom up approach is that there is supportive research for the circle theory and the classification of marauders and commuters. Canter and Larkin studied 45 sexual assaults and showed support for distinguishing between marauders and commuters. However over 90% of the offenders were classed as marauders. If most criminals are marauders then the classification seems useless.
Another researcher found flaws with the model. One being that if the offenders home base is not at the centre of the circle this means police may look in the wrong area which wastes police time and may give the offender more time to cover up the crime.
A weakness of using geographical profiling is that it may not actually be useful or successful. Rossmo is a supporter of the geographical approach and claims that although it may not solve crimes specifically it can be useful in prioritising house to house searches or identifying an area where DNA could be collected. However it can not distinguish between multiple offenders in the same area. Therefore if several criminals from the same area work together they may be able to get away with their crimes if investigators were using the geographical approach.
Also it only looks at spatial behaviour and not any personality characteristics so it may not offer more than the traditional method of placing pins on a map to see where a group of crimes were committed. This suggests that using geographical profiling alone to solve any crimes would not be useful as the approach can not solve crimes specifically
Overall the success rates of offender profiling and the views of police who have used the technique suggest that profiling can not reliably identify an offender but assists police in narrowing down the field of possibilities. However sticking too closely to any profile can be dangerous. Rachel nickell was stabbed to death and a forensic psychologist helped police create a profile which led to the identification of Colin stagg. It was later revealed after a lot of time and money spent that the murderer was someone else who had first been ruled out as he was taller than the picture given in the profile.
This therefore suggests that the police should not solely rely on a profile created and should be mindful of the fact that mistakes could have been made when constructing the profile.
