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By Use Case

AI for Legal Writing: Briefs, Contracts, Memos

Legal AI has the widest gap between individual and institutional adoption of any writing category. The 8am 2025 Report (a survey of 1,300+ legal professionals) found individual gen AI use jumped from 31% in 2024 to 69% in 2025. But Thomson Reuters' parallel global survey found only 26% of legal organizations actively integrating gen AI at the firm level. Harvey, the leading legal AI vendor, now serves over 1,500 global customers including most major Am Law 100 firms — but most lawyers inside those firms still use ChatGPT informally for tasks they don't tell their general counsel about. Hanging over the entire category: the 2023 Mata v. Avianca case, in which a New York law firm was fined $5,000 for filing a brief with six fictitious cases hallucinated by ChatGPT. This page tracks the adoption surge, the firm-level lag, and the hallucination risk that defines the category.

4 visualizations + signals card 7 sources Last updated June 2026 Free to embed
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Chart 2 · What lawyers use AI for

Top legal AI use cases by frequency

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Source: Thomson Reuters 2025 Generative AI Report; RSGI/Harvey 2025 independent adoption study (40 law firms surveyed). Document review consistently ranks as the most-used capability — AI completes in seconds tasks that take lawyers hours.
Chart 3 · Vendor traction

Harvey global customer growth, 2023–2025

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Source: Harvey 2025 Adoption Metrics Report; Harvey public funding announcements. 1,500+ global customers by end 2025, including most major Am Law 100 firms. Microsoft (Azure) and LexisNexis partnerships extended distribution; Harvey acquired RAG infrastructure as well to power agent workflows.

About this data

The AI Behavior Index is the research arm of OneChat AI. This page focuses on AI applied to legal writing — drafting briefs, contracts, memos, demand letters, and discovery responses — as well as legal research and document review, which feed into writing workflows. It draws on the 8am Legal Insight Report (n=1,300+, the largest recent survey of US legal professionals), Thomson Reuters' Generative AI Report (firm-level institutional data), Clio Legal Trends, RSGI/Harvey's independent adoption study, and Embroker's lawyer concerns survey.

Two methodological caveats matter. First, the 8am Report's 69% headline figure is heavily weighted to solo and small-firm practitioners — 83% of respondents came from firms with 5 or fewer lawyers. Large-firm individual lawyer adoption is likely lower than 69% but higher than the 28% firm-level Thomson Reuters figure; the true number sits somewhere in between, with no single survey covering it well. Second, the hallucination sanction count is necessarily incomplete — many sanctions are issued at the trial-court level and never make it into databases. The direction (rising) is clearer than the absolute number. Data is refreshed when major surveys publish. If you have a study to suggest or notice an error, contact us at research@aibehaviorindex.org.

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Every statistic shown is sourced from a publicly available study, survey, or report. We aggregate, organize, and contextualize this data — but the underlying research is conducted by the cited sources. Click any source link to access the original methodology. If you run into any issues or have a study to suggest, contact us at research@aibehaviorindex.org.