Place Matters: Comparing LLM Hallucination Rates for Place-Based Legal Queries

Fuente: arXiv
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Auteurs principaux: Curran, Damian, Sporne, Vanessa, Frermann, Lea, Paterson, Jeannie
Format: Preprint
Publié: 2025
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author Curran, Damian
Sporne, Vanessa
Frermann, Lea
Paterson, Jeannie
author_facet Curran, Damian
Sporne, Vanessa
Frermann, Lea
Paterson, Jeannie
contents How do we make a meaningful comparison of a large language model's knowledge of the law in one place compared to another? Quantifying these differences is critical to understanding if the quality of the legal information obtained by users of LLM-based chatbots varies depending on their location. However, obtaining meaningful comparative metrics is challenging because legal institutions in different places are not themselves easily comparable. In this work we propose a methodology to obtain place-to-place metrics based on the comparative law concept of functionalism. We construct a dataset of factual scenarios drawn from Reddit posts by users seeking legal advice for family, housing, employment, crime and traffic issues. We use these to elicit a summary of a law from the LLM relevant to each scenario in Los Angeles, London and Sydney. These summaries, typically of a legislative provision, are manually evaluated for hallucinations. We show that the rate of hallucination of legal information by leading closed-source LLMs is significantly associated with place. This suggests that the quality of legal solutions provided by these models is not evenly distributed across geography. Additionally, we show a strong negative correlation between hallucination rate and the frequency of the majority response when the LLM is sampled multiple times, suggesting a measure of uncertainty of model predictions of legal facts.
format Preprint
id arxiv_https___arxiv_org_abs_2511_06700
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Place Matters: Comparing LLM Hallucination Rates for Place-Based Legal Queries
Curran, Damian
Sporne, Vanessa
Frermann, Lea
Paterson, Jeannie
Computers and Society
Artificial Intelligence
Computation and Language
How do we make a meaningful comparison of a large language model's knowledge of the law in one place compared to another? Quantifying these differences is critical to understanding if the quality of the legal information obtained by users of LLM-based chatbots varies depending on their location. However, obtaining meaningful comparative metrics is challenging because legal institutions in different places are not themselves easily comparable. In this work we propose a methodology to obtain place-to-place metrics based on the comparative law concept of functionalism. We construct a dataset of factual scenarios drawn from Reddit posts by users seeking legal advice for family, housing, employment, crime and traffic issues. We use these to elicit a summary of a law from the LLM relevant to each scenario in Los Angeles, London and Sydney. These summaries, typically of a legislative provision, are manually evaluated for hallucinations. We show that the rate of hallucination of legal information by leading closed-source LLMs is significantly associated with place. This suggests that the quality of legal solutions provided by these models is not evenly distributed across geography. Additionally, we show a strong negative correlation between hallucination rate and the frequency of the majority response when the LLM is sampled multiple times, suggesting a measure of uncertainty of model predictions of legal facts.
title Place Matters: Comparing LLM Hallucination Rates for Place-Based Legal Queries
topic Computers and Society
Artificial Intelligence
Computation and Language
url https://arxiv.org/abs/2511.06700