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 ar- ticles 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 arti- cles (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 mur- der 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 simi- larity between cases for sentence estimation after fil- tering out inadequate factors by using previously re- trieved precedents. Finally we confirmed that using similarity-based weights gives less erroneous sentence estimation than the baseline method lacking those weights.