Adapting IndicTrans2 for Legal Domain MT via QLoRA Fine-Tuning at JUST-NLP 2025
Akoijam Jenil Singh, Loitongbam Sanayai Meetei, Yumnam Surajkanta
Abstract
Machine Translation (MT) in the legal domain presents substantial challenges due to its complex terminology, lengthy statutes, and rigid syntactic structures. The JUST-NLP 2025 Shared Task on Legal Machine Translation was organized to advance research on domain-specific MT systems for legal texts. In this work, we propose a fine-tuned version of the pretrained large language model (LLM) ai4bharat/indictrans2-en-indic-1B, a transformer-based English-to-Indic translation model. Fine-tuning was performed using the parallel corpus provided by the JUST-NLP 2025 Shared Task organizers.Our adapted model demonstrates notable improvements over the baseline system, particularly in handling domain-specific legal terminology and complex syntactic constructions. In automatic evaluation, our system obtained BLEU = 46.67 and chrF = 70.03.In human evaluation, it achieved adequacy = 4.085 and fluency = 4.006. Our approach achieved an AutoRank score of 58.79, highlighting the effectiveness of domain adaptation through fine-tuning for legal machine translation.- Anthology ID:
- 2025.justnlp-main.15
- Volume:
- Proceedings of the 1st Workshop on NLP for Empowering Justice (JUST-NLP 2025)
- Month:
- December
- Year:
- 2025
- Address:
- Mumbai, India
- Editors:
- Ashutosh Modi, Saptarshi Ghosh, Asif Ekbal, Pawan Goyal, Sarika Jain, Abhinav Joshi, Shivani Mishra, Debtanu Datta, Shounak Paul, Kshetrimayum Boynao Singh, Sandeep Kumar
- Venues:
- JUSTNLP | WS
- SIG:
- Publisher:
- Association for Computational Linguistics
- Note:
- Pages:
- 142–147
- Language:
- URL:
- https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.justnlp-main.15/
- DOI:
- Cite (ACL):
- Akoijam Jenil Singh, Loitongbam Sanayai Meetei, and Yumnam Surajkanta. 2025. Adapting IndicTrans2 for Legal Domain MT via QLoRA Fine-Tuning at JUST-NLP 2025. In Proceedings of the 1st Workshop on NLP for Empowering Justice (JUST-NLP 2025), pages 142–147, Mumbai, India. Association for Computational Linguistics.
- Cite (Informal):
- Adapting IndicTrans2 for Legal Domain MT via QLoRA Fine-Tuning at JUST-NLP 2025 (Singh et al., JUSTNLP 2025)
- PDF:
- https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.justnlp-main.15.pdf