PreprintCited by 156Artificial Intelligence in LawTopic ModelingLegal Education and Practice Innovations

Legalbench: A Collaboratively Built Benchmark for Measuring Legal Reasoning in Large Language Models

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Guha, Neel, Nyarko, Julian, Ho, Daniel E., Ré, Christopher, Chilton, Adam, Narayana, Aditya, Chohlas-Wood, Alex, Peters, Austin +32 more·2023·SSRN Electronic Journal

Abstract

The advent of large language models (LLMs) and their adoption by the legal community has given rise to the question: what types of legal reasoning can LLMs perform? To enable greater study of this question, we present LegalBench: a collaboratively constructed legal reasoning benchmark consisting of 162 tasks covering six different types of legal reasoning. LegalBench was built through an interdisciplinary process, in which we collected tasks designed and hand-crafted by legal professionals. Because these subject matter experts took a leading role in construction, tasks either measure legal reasoning capabilities that are practically useful, or measure reasoning skills that lawyers find interesting. To enable cross-disciplinary conversations about LLMs in the law, we additionally show how popular legal frameworks for describing legal reasoning—which distinguish between its many forms—correspond to LegalBench tasks, thus giving lawyers and LLM developers a common vocabulary. This paper describes LegalBench, presents an empirical evaluation of 20 open-source and commercial LLMs, and illustrates the types of research explorations LegalBench enables.

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Crossref · 10.2139/ssrn.4583531

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  • Lawyers are often taught to analyze situations with an IRAC framework-first identify the issue and governing legal rule, then analyze the facts with that rule to arrive at a conclusion.

    “Lawyers are often taught to analyze situations with an IRAC framework-first identify the issue (I) and governing legal rule (R), then analyze (A) the facts with that rule to arrive at a conclusion (C) (Guha et al. 2023).”

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Authors
Guha, N., Nyarko, J., Ho, D. E., Ré, C., Chilton, A., Narayana, A., Chohlas-Wood, A., Peters, A., Waldon, B., Rockmore, D., Zambrano, D., Talisman, D., Hoque, E., Surani, F., Fagan, F., Sarfaty, G., Dickinson, G. M., Porat, H., Hegland, J., Wu, J., Nudell, J., Niklaus, J., Nay, J., Choi, J. H., Tobia, K., Hagan, M., Ma, M., Livermore, M. A., Rasumov-Rahe, N., Holzenberger, N., Kolt, N., Henderson, P., Rehaag, S., Goel, S., Gao, S., Williams, S., Gandhi, S., Zur, T., Iyer, V., & Li, Z.
Affiliations
  • Stanford University (US)
  • University of Chicago (US)
  • Georgetown University (US)
  • Dartmouth College (US)
  • University of California, Santa Barbara (US)
  • South Texas College of Law (US)
  • University of Toronto (CA)
  • University of Nebraska–Lincoln (US)
  • Harvard University (US)
  • University of Bern (CH)
  • New York University (US)
  • University of Minnesota (US)
  • University of Virginia (US)
  • Institut Polytechnique de Paris (FR)
  • Princeton University (US)
  • York University (CA)
  • California Western School of Law (US)
  • Indiana University Bloomington (US)
Corresponding author
Guha, Neel
Venue
SSRN Electronic Journal
Publisher
Elsevier BV
Published
2023
Volume
4583531
Pages
1-143
ISSN
1556-5068 (ISSN-L)
OpenAlex
W4389403907
Cited by
154
References
106
Citations by year
2026: 36 · 2025: 74 · 2024: 38 · 2023: 6
Type
posted content
Language
en
Open access
Locations
  • SSRN Electronic Journal (acceptedVersion)
  • HAL (submittedVersion)
  • bepress Legal Repository (submittedVersion)
Topics
  • Social Sciences › Political Science and International Relations › Artificial Intelligence in Law
  • Physical Sciences › Computer Science › Artificial Intelligence › Topic Modeling
  • Social Sciences › Law › Legal Education and Practice Innovations
Keywords
legal reasoning, large language models, benchmark design, lawyers, LLM evaluation, interdisciplinary collaboration

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