Hallucination Detectives at SemEval-2025 Task 3: Span-Level Hallucination Detection for LLM-Generated Answers

Passant Elchafei, Mervat Abu - Elkheir


Abstract
Detecting spans of hallucination in LLM-generated answers is crucial for improving factual consistency. This paper presents a span-level hallucination detection framework for the SemEval-2025 Shared Task, focusing on English and Arabic texts. our approach integrates Semantic Role Labeling (SRL) to decompose the answer into atomic roles, which are then compared with a retrieved reference context obtained via question-based LLM prompting. Using a DeBERTa-based textual entailment model, we evaluate each role’s semantic alignment with the retrieved context. The entailment scores are further refined through token-level confidence measures derived from output logits, and the combined scores are used to detect hallucinated spans. Experiments on the Mu-SHROOM dataset demonstrate competitive performance. Additionally, hallucinated spans have been verified through fact-checking by prompting GPT-4 and LLaMA. Our findings contribute to improving hallucination detection in LLM-generated responses.
Anthology ID:
2025.semeval-1.84
Volume:
Proceedings of the 19th International Workshop on Semantic Evaluation (SemEval-2025)
Month:
July
Year:
2025
Address:
Vienna, Austria
Editors:
Sara Rosenthal, Aiala Rosá, Debanjan Ghosh, Marcos Zampieri
Venues:
SemEval | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
601–606
Language:
URL:
https://preview.aclanthology.org/transition-to-people-yaml/2025.semeval-1.84/
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Bibkey:
Cite (ACL):
Passant Elchafei and Mervat Abu - Elkheir. 2025. Hallucination Detectives at SemEval-2025 Task 3: Span-Level Hallucination Detection for LLM-Generated Answers. In Proceedings of the 19th International Workshop on Semantic Evaluation (SemEval-2025), pages 601–606, Vienna, Austria. Association for Computational Linguistics.
Cite (Informal):
Hallucination Detectives at SemEval-2025 Task 3: Span-Level Hallucination Detection for LLM-Generated Answers (Elchafei & Abu - Elkheir, SemEval 2025)
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https://preview.aclanthology.org/transition-to-people-yaml/2025.semeval-1.84.pdf