Cited but Not Consulted: A Counterfactual Audit of Legal Chain-of-Thought Faithfulness
Large language models increasingly justify legal decisions by naming the statute or precedent behind a verdict, treated as evidence that the decision follows from it. We test this directly: holding case facts fixed, we substitute the named legal authority for an unrelated one and decode a model's evolving verdict from its hidden states. Across seven open-weight models (8B-70B) and four benchmarks spanning judicial and contractual reasoning, when explicitly required to justify a verdict by naming the governing authority, models name the correct one in 66.7%-100% of generations, while the verdict changing when the authority changes is far less consistent: 0.0%-21.7% on CaseHOLD, 30.0%-76.7% on ECHR and SCOTUS, and 43.3%-50.0% on ContractNLI. Neither scale nor a purpose-built legal-reasoning
研究测试了语言模型在改变法律依据时的判决变化一致性。
- 核心方法
- 固定案例事实，替换模型引用的法律权威为无关内容，观察模型判决的变化情况。
- 适合谁读
- 研究者、法律领域工程师
- 要解决的问题
- 大型语言模型在做出法律判决时是否真正依赖所引用的法律依据，还是仅仅形式上引用。
- 关键实验
- 在七个开放权重模型（8B-70B参数）上进行了测试，涵盖了四个不同的法律推理基准（CaseHOLD、ECHR、SCOTUS、ContractNLI）。
- 主要贡献
- 揭示了语言模型在法律推理中对具体法律依据的依赖程度较低，质疑了其解释的忠实性。
- 意义与局限
- 该研究对于理解语言模型在法律应用中的可靠性和局限性具有重要意义，但未提供解决方案以提高模型的依赖性。