用大模型提升法律判决预测的因果推理能力,解决噪声干扰与结构模糊问题。
LLM-Assisted Causal Structure Disambiguation and Factor Extraction for Legal Judgment Prediction
- 结合统计抽样与大模型语义推理,精准提取法律要素
- 利用大模型作为先验知识,消除因果结构不确定性
- 通过因果图约束注意力,提升模型在混淆罪名上的判别力
基于预训练语言模型的法律判决预测方法主要依赖案件事实与判决结果之间的统计相关性,缺乏对法律构成要件和深层因果逻辑的显式建模,易学习虚假关联且鲁棒性差。尽管引入因果推断可缓解此问题,现有因果法律判决方法在真实法律文本中仍面临两大瓶颈:法律要素提取噪声严重、稀疏特征下因马尔可夫等价导致因果结构发现存在显著不确定性。为此,我们提出一种融合大语言模型先验与统计因果发现的增强型因果推理框架。首先,设计粗粒度到细粒度的混合抽取机制,结合统计采样与大模型语义推理,精准识别并净化标准法律构成要件。其次,为解决结构不确定性,引入大模型辅助的因果结构消歧机制,利用大模型作为受约束的先验知识库,对模糊的因果方向进行概率评估与剪枝,生成符合法律规范的候选因果图。最后,通过生成的因果图显式约束文本注意力强度,构建因果感知的判决预测模型。在LEVEN、QA和CAIL等多个基准数据集上的大量实验表明,所提方法在预测准确率和鲁棒性方面均显著优于现有最先进基线,尤其在区分相似罪名时表现突出。
原文摘要 · Abstract (English)
Mainstream methods for Legal Judgment Prediction (LJP) based on Pre-trained Language Models (PLMs) heavily rely on the statistical correlation between case facts and judgment results. This paradigm lacks explicit modeling of legal constituent elements and underlying causal logic, making models prone to learning spurious correlations and suffering from poor robustness. While introducing causal inference can mitigate this issue, existing causal LJP methods face two critical bottlenecks in real-world legal texts: inaccurate legal factor extraction with severe noise, and significant uncertainty in causal structure discovery due to Markov equivalence under sparse features. To address these challenges, we propose an enhanced causal inference framework that integrates Large Language Model (LLM) priors with statistical causal discovery. First, we design a coarse-to-fine hybrid extraction mechanism combining statistical sampling and LLM semantic reasoning to accurately identify and purify standard legal constituent elements. Second, to resolve structural uncertainty, we introduce an LLM-assisted causal structure disambiguation mechanism. By utilizing the LLM as a constrained prior knowledge base, we conduct probabilistic evaluation and pruning on ambiguous causal directions to generate legally compliant candidate causal graphs. Finally, a causal-aware judgment prediction model is constructed by explicitly constraining text attention intensity via the generated causal graphs. Extensive experiments on multiple benchmark datasets, including LEVEN , QA, and CAIL, demonstrate that our proposed method significantly outperforms state-of-the-art baselines in both predictive accuracy and robustness, particularly in distinguishing confusing charges.
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