U-CREAT: Unsupervised Case Retrieval using Events extrAcTion

Abhinav Joshi, Akshat Sharma, Sai Kiran Tanikella, Ashutosh Modi


Abstract
The task of Prior Case Retrieval (PCR) in the legal domain is about automatically citing relevant (based on facts and precedence) prior legal cases in a given query case. To further promote research in PCR, in this paper, we propose a new large benchmark (in English) for the PCR task: IL-PCR (Indian Legal Prior Case Retrieval) corpus. Given the complex nature of case relevance and the long size of legal documents, BM25 remains a strong baseline for ranking the cited prior documents. In this work, we explore the role of events in legal case retrieval and propose an unsupervised retrieval method-based pipeline U-CREAT (Unsupervised Case Retrieval using Events Extraction). We find that the proposed unsupervised retrieval method significantly increases performance compared to BM25 and makes retrieval faster by a considerable margin, making it applicable to real-time case retrieval systems. Our proposed system is generic, we show that it generalizes across two different legal systems (Indian and Canadian), and it shows state-of-the-art performance on the benchmarks for both the legal systems (IL-PCR and COLIEE corpora).
Anthology ID:
2023.acl-long.777
Volume:
Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)
Month:
July
Year:
2023
Address:
Toronto, Canada
Editors:
Anna Rogers, Jordan Boyd-Graber, Naoaki Okazaki
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
13899–13915
Language:
URL:
https://aclanthology.org/2023.acl-long.777
DOI:
10.18653/v1/2023.acl-long.777
Bibkey:
Cite (ACL):
Abhinav Joshi, Akshat Sharma, Sai Kiran Tanikella, and Ashutosh Modi. 2023. U-CREAT: Unsupervised Case Retrieval using Events extrAcTion. In Proceedings of the 61st Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers), pages 13899–13915, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
U-CREAT: Unsupervised Case Retrieval using Events extrAcTion (Joshi et al., ACL 2023)
Copy Citation:
PDF:
https://aclanthology.org/2023.acl-long.777.pdf
Video:
 https://aclanthology.org/2023.acl-long.777.mp4