@inproceedings{buakhaw-etal-2026-deka,
title = "Deka Retrieval: Component-Level Criteria for Mining Legal Case Pairs in {T}hai {S}upreme {C}ourt Decisions",
author = "Buakhaw, Pasin and
Akarajaradwong, Pawitsapak and
Chaksangchaichot, Chompakorn",
editor = "Aletras, Nikolaos and
Chalkidis, Ilias and
Barrett, Leslie and
Goanț{\u{a}}, C{\u{a}}t{\u{a}}lina and
Preoțiuc-Pietro, Daniel and
Spanakis, Gerasimos and
Xu, Shanshan",
booktitle = "Proceedings of the Natural Legal Language Processing Workshop 2026",
month = oct,
year = "2026",
address = "Budapest, Hungary",
publisher = "Association for Computational Linguistics",
url = "https://aclanthology.org/2026.nllp-1.35/",
pages = "399--419",
ISBN = "979-8-89176-494-1",
abstract = "Legal case retrieval (LCR) defines relevance beyond text similarity, judgments may describe near-identical events yet be decided under different charges. Existing synthesis pipelines mine training pairs from text similarity and shared charges, which separates positives from negatives but leaves the difficulty of each pair implicit. We present Deka Retrieval, an LCR benchmark on Thai Supreme Court decisions with an LLM relevance cases mining pipeline for a civil-law jurisdiction. We decompose each judgment into case components (Charge, Fact, Reasoning, Decision) and split easy/hard level on exist binary signals and introduce an anomaly variant a conflict judgment that shares the anchor{'}s charge and facts but reaching a different reasoning and decision. Retriever performance follows query length: Fact {\ensuremath{>}} Lawyer expert {\ensuremath{>}} Lay people. Fine-tuning gains most on the weakest type, lifting Lay R@10 by 2.6x (7.6 -{\ensuremath{>}} 19.5) versus 1.5x on Lawyer and 1.3x on Fact. Training on the shortest query also transfers to the longer ones, but not the reverse. Adding anomaly cases as positives raises the chance of retrieving them at test time and degrades performance relative to training without them. Our dataset and models are available at https://hf.co/collections/VISAI-AI/deka-retrieval."
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<abstract>Legal case retrieval (LCR) defines relevance beyond text similarity, judgments may describe near-identical events yet be decided under different charges. Existing synthesis pipelines mine training pairs from text similarity and shared charges, which separates positives from negatives but leaves the difficulty of each pair implicit. We present Deka Retrieval, an LCR benchmark on Thai Supreme Court decisions with an LLM relevance cases mining pipeline for a civil-law jurisdiction. We decompose each judgment into case components (Charge, Fact, Reasoning, Decision) and split easy/hard level on exist binary signals and introduce an anomaly variant a conflict judgment that shares the anchor’s charge and facts but reaching a different reasoning and decision. Retriever performance follows query length: Fact \ensuremath> Lawyer expert \ensuremath> Lay people. Fine-tuning gains most on the weakest type, lifting Lay R@10 by 2.6x (7.6 -\ensuremath> 19.5) versus 1.5x on Lawyer and 1.3x on Fact. Training on the shortest query also transfers to the longer ones, but not the reverse. Adding anomaly cases as positives raises the chance of retrieving them at test time and degrades performance relative to training without them. Our dataset and models are available at https://hf.co/collections/VISAI-AI/deka-retrieval.</abstract>
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%0 Conference Proceedings
%T Deka Retrieval: Component-Level Criteria for Mining Legal Case Pairs in Thai Supreme Court Decisions
%A Buakhaw, Pasin
%A Akarajaradwong, Pawitsapak
%A Chaksangchaichot, Chompakorn
%Y Aletras, Nikolaos
%Y Chalkidis, Ilias
%Y Barrett, Leslie
%Y Goanță, Cătălina
%Y Preoțiuc-Pietro, Daniel
%Y Spanakis, Gerasimos
%Y Xu, Shanshan
%S Proceedings of the Natural Legal Language Processing Workshop 2026
%D 2026
%8 October
%I Association for Computational Linguistics
%C Budapest, Hungary
%@ 979-8-89176-494-1
%F buakhaw-etal-2026-deka
%X Legal case retrieval (LCR) defines relevance beyond text similarity, judgments may describe near-identical events yet be decided under different charges. Existing synthesis pipelines mine training pairs from text similarity and shared charges, which separates positives from negatives but leaves the difficulty of each pair implicit. We present Deka Retrieval, an LCR benchmark on Thai Supreme Court decisions with an LLM relevance cases mining pipeline for a civil-law jurisdiction. We decompose each judgment into case components (Charge, Fact, Reasoning, Decision) and split easy/hard level on exist binary signals and introduce an anomaly variant a conflict judgment that shares the anchor’s charge and facts but reaching a different reasoning and decision. Retriever performance follows query length: Fact \ensuremath> Lawyer expert \ensuremath> Lay people. Fine-tuning gains most on the weakest type, lifting Lay R@10 by 2.6x (7.6 -\ensuremath> 19.5) versus 1.5x on Lawyer and 1.3x on Fact. Training on the shortest query also transfers to the longer ones, but not the reverse. Adding anomaly cases as positives raises the chance of retrieving them at test time and degrades performance relative to training without them. Our dataset and models are available at https://hf.co/collections/VISAI-AI/deka-retrieval.
%U https://aclanthology.org/2026.nllp-1.35/
%P 399-419
Markdown (Informal)
[Deka Retrieval: Component-Level Criteria for Mining Legal Case Pairs in Thai Supreme Court Decisions](https://aclanthology.org/2026.nllp-1.35/) (Buakhaw et al., NLLP 2026)
ACL