On the importance of Legal Catchphrases in Precedence Retrieval

This paper presents our working notes for FIRE 2017, Information Retrieval from Legal documents -Task 2 (Precedence retrieval). Common Law Systems around the world recognize the importance of precedence in Law. In making decisions, Judges are obliged to consult prior cases that had already been decided to ensure that there is no divergence in treatment of similar situations in different cases. Our approach was to investigate the effectiveness of using legal catchphrases in precedence retrieval. To improve retrieval performance, we incorporated term dependency in our retrieval. In addition, we investigate the effects of deploying query expansion on the retrieval performance. Our results show an improvement in the retrieval performance when we incorporate term dependence in scoring and ranking prior cases. However, we see a degradation in the retrieval performance when we deploy query expansion.