Toward Automatic Support For Japanese Lay Judge System - Processing Precedent Factors For Sentencing Trends Discovery

In this paper we investigate factors that influence trends in sentencing process basing on newspaper articles in order to find lexical clues for automatic trial verdict estimation. We examine verdicts for murder cases of the last 10 years using 149 newspaper articles (1998-2001) and 160 precedents from a database available online (2001-2007). The results showed that there is a tendency to give stricter verdicts for murder cases and clustered by CLUTO into five classes were judged as descriptive factors related to a crime method and lethal weapon usage. We also use similarity between cases for sentence estimation after filtering out inadequate factors by using previously retrieved precedents. Finally we confirmed that using similarity-based weights gives less erroneous sentence estimation than the baseline method lacking those weights.