A neural network program then uses this to seek out crimes with similar profiles. The neural network the DePaul team uses, called a Kohonen network, is particularly good at finding patterns in a set of input data without any human intervention, Muscarello says. Some neural networks require an operator to "train" them to find patterns in data sets - but this requires foreknowledge of the pattern. If it finds a possible link between two crimes, CSSCP compares when and where they took place to find out whether the same criminals would have had enough time to travel from one crime scene to the other. In a ring-fenced lab trial of the system using three years' worth of data on armed robbery- it wasn't operating on a live police network- Muscarello claims the system was able to spot 10 times as many patterns as a team of detectives with access to the same data. Muscarello stresses that CSSCP will not replace human detectives. It simply provides a starting point for detectives by flagging potentially related crimes. While detectives could probably identify the same patterns, the sheer mass of available data usually makes this too time-consuming. In the UK an online version of a manually searchable crime database called Crimelink was launched this week. But while Crimelink can be used to search for specified patterns of criminal activity- querying if, say, a certain type of car has been used in armed robberies in Cambridge- it will not search for similarities that have not been suggested by a human operator.
Muscarello is now hoping to convince the Chicago police department to run trials of the system. Feedback from six leading detectives in the Chicago area have been positive, and he says one reason for this is that the researchers consulted detectives on how the system should work. "To a certain extent we based it on the way detectives solve these crimes," Muscarello says. In conventional investigations, the work of finding a pattern may be split between several detectives, with each one handling a different aspect of the case. For example, one might focus on the witnesses or victims, while another might try to trace a getaway vehicle. CSSCP can do the same by applying different neural networks to find patterns in different facets of the investigation. The amount of information being filed for each crime is constantly increasing, says John Kingston, director of the Joseph Bell Centre for Forensic Statistics and Legal Reasoning at the University of Edinburgh, UK. This means that "data mining" is likely to become increasingly necessary in crimefighting, he predicts.
Written by DUNCAN GRAHAM-ROWE
This article appears in New Scientist issue: 4 December 2004
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