Hallucination-Free? Assessing the Reliability of Leading AI Legal Research Tools

Authors: Varun Magesh, Faiz Surani, Matthew Dahl, Mirac Suzgun, Christopher D. Manning, Daniel E. Ho

Our dataset, tool outputs, and labels will be made available upon publication. This version of the manuscript (May 30, 2024) is updated to reflect an evaluation of Westlaw's AI-Assisted Research
License: CC BY 4.0

Results of the summarizing process for the arXiv paper: 2405.20362v1

  • Comprehensive Summary
  • Key points
  • Layman's Summary
  • Blog article
Legal practice has seen a significant increase in the use of artificial intelligence (AI) tools to assist with various legal tasks, such as legal research and document drafting. However, these AI tools, particularly those using large language models, are prone to "hallucinate," or generate false information, which poses risks in high-stakes legal domains. Some legal research providers have claimed that methods like retrieval-augmented generation (RAG) can eliminate or avoid hallucinations in their AI tools. A recent empirical evaluation of AI-driven legal research tools by researchers revealed that while hallucinations were reduced compared to general-purpose chatbots like GPT-4, popular AI tools like LexisNexis' Lexis+ AI and Thomson Reuters' Westlaw AI-Assisted Research and Ask Practical Law AI still exhibited hallucination rates between 17% and 33%. The study also highlighted differences in responsiveness and accuracy among these systems. The limitations of RAG in the legal domain were discussed in detail. Retrieval in law is complex due to the lack of clear-cut answers in legal queries and the evolving nature of case law. Document relevance is not solely based on text similarity but also on contextual factors specific to different jurisdictions and time periods. Generating meaningful legal text requires synthesizing facts, holdings, and rules from various sources while maintaining the appropriate legal context. Furthermore, challenges such as closed systems restricting access to interfaces and the need for manual evaluation of results hinder automated evaluations of legal AI tools. Despite advancements in LLM-based evaluations, the legal AI product space remains largely closed off. In conclusion, this detailed analysis sheds light on the limitations of RAG-based proprietary legal AI tools and emphasizes the importance of understanding vulnerabilities in these systems. It also underscores the need for legal professionals to supervise and verify AI outputs effectively for responsible integration into law practices.
AI-generated keywords: Legal practice Artificial intelligence Hallucinations Retrieval-augmented generation (RAG) Limitations

AI-generated Key Points

  • Legal practice increasingly relies on AI tools for tasks like research and document drafting
  • AI tools, especially those using large language models, can generate false information (hallucinations) in high-stakes legal domains
  • Some providers claim methods like retrieval-augmented generation (RAG) can reduce hallucinations
  • Empirical evaluation showed popular AI tools still exhibit hallucination rates between 17% and 33%
  • Retrieval in law is complex due to lack of clear-cut answers and evolving case law
  • Generating meaningful legal text requires synthesizing facts, holdings, and rules while maintaining legal context
  • Challenges include closed systems limiting access and the need for manual evaluation of results
  • Legal AI product space remains largely closed off despite advancements in evaluations
  • Importance of understanding vulnerabilities in legal AI tools and effective supervision by professionals
Also access our AI generated: Comprehensive summary, Lay summary, Blog-like article; or ask questions about this paper to our AI assistant.

Abstract: Legal practice has witnessed a sharp rise in products incorporating artificial intelligence (AI). Such tools are designed to assist with a wide range of core legal tasks, from search and summarization of caselaw to document drafting. But the large language models used in these tools are prone to "hallucinate," or make up false information, making their use risky in high-stakes domains. Recently, certain legal research providers have touted methods such as retrieval-augmented generation (RAG) as "eliminating" (Casetext, 2023) or "avoid[ing]" hallucinations (Thomson Reuters, 2023), or guaranteeing "hallucination-free" legal citations (LexisNexis, 2023). Because of the closed nature of these systems, systematically assessing these claims is challenging. In this article, we design and report on the first preregistered empirical evaluation of AI-driven legal research tools. We demonstrate that the providers' claims are overstated. While hallucinations are reduced relative to general-purpose chatbots (GPT-4), we find that the AI research tools made by LexisNexis (Lexis+ AI) and Thomson Reuters (Westlaw AI-Assisted Research and Ask Practical Law AI) each hallucinate between 17% and 33% of the time. We also document substantial differences between systems in responsiveness and accuracy. Our article makes four key contributions. It is the first to assess and report the performance of RAG-based proprietary legal AI tools. Second, it introduces a comprehensive, preregistered dataset for identifying and understanding vulnerabilities in these systems. Third, it proposes a clear typology for differentiating between hallucinations and accurate legal responses. Last, it provides evidence to inform the responsibilities of legal professionals in supervising and verifying AI outputs, which remains a central open question for the responsible integration of AI into law.

Submitted to arXiv on 30 May. 2024

Tools for this paper

Explain it differently 3 free rewrites left today
Export BibTeX · RIS (Zotero, Mendeley, EndNote) · Markdown (Notion, Obsidian) · Premium
Citation alerts Premium
Journal club Slides to present it Premium
For journalists Press kit and hype check Premium

Ask questions about this paper to our AI assistant

You can also chat with multiple papers at once here.

Figures and plots

Ask about a figure by number or use its question button to request visual analysis. Up to two figures and four image panels per question. Values read from plots are approximate; check the original data.

AI assistant instructions?

Assess the quality of the AI-generated content by voting

Score: 0

Why do we need votes?

Votes are used to determine whether we need to re-run our summarizing tools. If the count reaches -10, our tools can be restarted.

The previous summary was created more than a year ago and can be re-run (if necessary) by clicking on the Run button below.

Similar papers summarized with our AI tools

Navigate through even more similar papers through a

tree representation

Disclaimer: The AI-based summarization tool and virtual assistant provided on this website may not always provide accurate and complete summaries or responses. We encourage you to carefully review and evaluate the generated content to ensure its quality and relevance to your needs.