Reproduce “LegalSearchLM: Rethinking Legal Case Retrieval as Legal Elements Generation” on OpenResearch

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About this paper

Chaeeun Kim, Jinu Lee, Wonseok Hwang

LBOX and the University of Illinois Urbana-Champaign introduced LegalSearchLM, a generative retrieval model for legal case retrieval that re-conceptualizes the task as generating key legal elements, and developed LEGAR BENCH, a large-scale Korean legal benchmark. LegalSearchLM achieved a Precision@5 of 0.68 on LEGAR BENCH_Standard, outperforming strong baselines like Contriever by 20 percentage points, and demonstrated robust generalization to unseen crime types.

Key insights

  • Reframing legal case retrieval as a generative task, focusing on specific legal elements, aligns more closely with how legal professionals determine relevance, mitigating information loss and improving semantic precision.
  • Self-supervised fine-tuning on legal elements from query cases enhances generalization across diverse and rare crime types by teaching the model to reason over legal components.
  • Integrating constrained beam decoding with an FM-index ensures that all generated legal elements are directly verifiable within the target corpus, providing strong grounding and preventing hallucinations.

Summary by alphaXiv.

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