SubmissionNumber#=%=#243 FinalPaperTitle#=%=#Archimedes-AUEB at SemEval-2024 Task 5: LLM explains Civil Procedure ShortPaperTitle#=%=# NumberOfPages#=%=#16 CopyrightSigned#=%=#Odysseas S. Chlapanis JobTitle#==# Organization#==# Abstract#==#The SemEval task on Argument Reasoning in Civil Procedure is challenging in that it requires understanding legal concepts and inferring complex arguments. Currently, most Large Language Models (LLM) excelling in the legal realm are principally purposed for classification tasks, hence their reasoning rationale is subject to contention. The approach we advocate involves using a powerful teacher-LLM (ChatGPT) to extend the training dataset with explanations and generate synthetic data. The resulting data are then leveraged to fine-tune a small student-LLM. Contrary to previous work, our explanations are not directly derived from the teacher's internal knowledge. Instead they are grounded in authentic human analyses, therefore delivering a superior reasoning signal. Additionally, a new `mutation' method generates artificial data instances inspired from existing ones. We are publicly releasing the explanations as an extension to the original dataset, along with the synthetic dataset and the prompts that were used to generate both. Our system ranked 15th in the SemEval competition. It outperforms its own teacher and can produce explanations aligned with the original human analyses, as verified by legal experts. Author{1}{Firstname}#=%=#Odysseas S. Author{1}{Lastname}#=%=#Chlapanis Author{1}{Username}#=%=#odychlapanis Author{1}{Email}#=%=#odyhlapanis@aueb.gr Author{1}{Affiliation}#=%=#Department of Informatics, Athens University of Economics and Business & Archimedes Unit, Athena Research Center Author{2}{Firstname}#=%=#Ion Author{2}{Lastname}#=%=#Androutsopoulos Author{2}{Email}#=%=#ion@aueb.gr Author{2}{Affiliation}#=%=#Department of Informatics, Athens University of Economics and Business & Archimedes Unit, Athena Research Center Author{3}{Firstname}#=%=#Dimitrios Author{3}{Lastname}#=%=#Galanis Author{3}{Email}#=%=#galanisd@athenarc.gr Author{3}{Affiliation}#=%=#Institute for Language and Speech Processing, Athena Research Center & Archimedes Unit, Athena Research Center ========== èéáğö