Abstract
In the case of arson, the police often have difficulty in finding forensic evidence and eyewitnesses. If the police can identify the suspects based on their crime scene behaviours, it will be helpful for the criminal investigation.
As the first step to fulfill the above purpose, this study focused on the behavioural characteristics of the Japanese repeat arsonists. It examined their behavioural consistency using the suspect retrieval support system developed by Adachi and his colleagues (1993, 1996, 1997). The system estimated behavioural similarities between a target sample and a database containing prior offenders and their offences, using the random choice probability method.
The data comprised arsonists who had committed crimes between 1982 and 2005. Three hundred and nineteen repeat arsonists were the target sample in the above system. The offences in the database numbered 10,237, and these crimes were committed by 10,154 arsonists.
Fifteen out of the 319 repeat arsonists were retrieved as a rank score of 1 among 10,154 offenders in the database, based on the similarity. The past records of 170 repeat arsonists were ranked within 10th percentile in the database. Additionally, an examination of the offenders who had more than one offence recorded in the database revealed that the most recent crimes among the offences committed by the same offender were most similar to the target crimes.
The consistency in the characteristics of each offence were compared by performing a chi-squared test between 81 offenders who showed the highest similarity and 81 offenders who showed the lowest similarity, differentiated by the suspect retrieval support system. The results showed that consistencies regarding the following behavioural characteristics showed highly significant differences between the two groups: the tools used and the way in which the fires were set, the objects burned, and the towns where the arsonists committed their crimes.
