LeCoPCR: Legal Concept-guided Prior Case Retrieval for European Court of Human Rights cases

2025-01-23

AI Summary

Existing case law retrieval methods for the European Court of Human Rights (ECtHR) neglect legal semantic intent, leading to inaccurate relevance judgments and hindering both legal professionals’ efficient case searching and secondary-school students’ comprehension. To address this, we propose a legal-concept-guided precedent retrieval framework: (1) it explicitly models the legal intent of queries via conceptualized representations; (2) it introduces a weakly supervised key concept extraction method based on Determinantal Point Processes (DPP), optimizing for both conceptual quality and diversity without annotated data; and (3) it integrates concept generation with semantic-enhanced retrieval. Evaluated on the ECtHR-PCR dataset, our approach achieves significant improvements in retrieval accuracy. Results validate the effectiveness of legal-concept guidance and DPP-driven concept extraction, establishing an interpretable and generalizable semantic modeling paradigm for case law retrieval.

Technology Category

• Data Mining & Knowledge Management: Conversational Systems for Recommendation & Retrieval
• Natural Language Processing: Information Extraction
• Cognitive Modeling & Cognitive Systems: Conceptual Inference and Reasoning

Application Category

• Search and Retrieval-Augmented AI: Web evaluation methodologies and metrics
• Semantics and Knowledge: Methods to enhance, augment, integrate or synergize semantic models such as knowledge graphs and LLMs
• User Modeling, Personalization and Recommendation: Fairness-aware retrieval and ranking

Abstract

Prior case retrieval (PCR) is crucial for legal practitioners to find relevant precedent cases given the facts of a query case. Existing approaches often overlook the underlying semantic intent in determining relevance with respect to the query case. In this work, we propose LeCoPCR, a novel approach that explicitly generate intents in the form of legal concepts from a given query case facts and then augments the query with these concepts to enhance models understanding of semantic intent that dictates relavance. To overcome the unavailability of annotated legal concepts, we employ a weak supervision approach to extract key legal concepts from the reasoning section using Determinantal Point Process (DPP) to balance quality and diversity. Experimental results on the ECtHR-PCR dataset demonstrate the effectiveness of leveraging legal concepts and DPP-based key concept extraction.

Problem

• European Court of Human Rights
• case law retrieval
• legal precedent understanding

Innovation

• LeCoPCR
• Semantic Association
• Weak Supervision