A Comparative Analysis of Large Language Models for Extracting Judicial Entities

Abstract

Legal judgments contain rich structured information, but the content is typically embedded inside long, formal narrative text. Named Entity Recognition (NER) is therefore a practical building block for legal search, analytics, and document understanding. In Pakistan, however, there is limited comparative evidence showing how well current large language model (LLM) services extract judicial entities from Lahore High Court (LHC) judgments under consistent experimental conditions.

This thesis benchmarks four LLM families, ChatGPT, Gemini, Grok, and DeepSeek, for prompt-only judicial NER on a corpus of 500 LHC judgments. A 22-type entity schema is defined to reflect common information needs in case law, including parties, judges, citations, acts, sections, and dates. Gold labels are produced as token-level IOB tags and then converted into a gold JSON representation with reconstructed entity spans and offsets. For model inference, a batch API application submits a unified prompt template to each model and converts responses into a standardized prediction JSON format. A separate evaluation application matches prediction JSON against the gold JSON using strict span-level exact match rules and reports micro-averaged precision, recall, and F1, supported by qualitative error analysis.

Results show that the top three models perform closely under strict scoring, with Grok achieving the highest micro F1 (0.6854), followed by Gemini (0.6820) and ChatGPT (0.6783), while DeepSeek scores lower (0.5790). ChatGPT produces the highest precision (0.7366), whereas Grok and Gemini achieve higher recall (0.6628 and 0.6534), indicating different operating points that matter for deployment. The error analysis highlights recurring legal-specific challenges, particularly span boundary drift, citation formatting variability, and confusions among closely related legal labels.

Overall, the thesis provides a reproducible, schema-driven benchmarking pipeline for Pakistani legal NLP and offers practical guidance on selecting and integrating LLM-based extraction into legal information systems where precision, recall, and auditability must be balanced.

Keywords: legal NLP, judicial named entity recognition, Lahore High Court, large language models, IOB tagging, prompt-based information extraction, evaluation pipeline