Enhancing Legal Argument Mining with Domain Pre-training and Neural Networks

TL;DR

This paper evaluates various embedding models, including domain-specific BERT variants and neural networks, for legal argument mining in European Court of Human Rights case law, highlighting the potential of domain pre-trained transformers.

Contribution

It provides a comprehensive comparison of classic and contextual embeddings with neural networks for legal argument mining, emphasizing the effectiveness of domain pre-trained transformer models.

Findings

Domain pre-trained transformers show strong potential.

Traditional embeddings perform well with neural networks.

Neural networks enhance the performance of various embeddings.

Abstract

The contextual word embedding model, BERT, has proved its ability on downstream tasks with limited quantities of annotated data. BERT and its variants help to reduce the burden of complex annotation work in many interdisciplinary research areas, for example, legal argument mining in digital humanities. Argument mining aims to develop text analysis tools that can automatically retrieve arguments and identify relationships between argumentation clauses. Since argumentation is one of the key aspects of case law, argument mining tools for legal texts are applicable to both academic and non-academic legal research. Domain-specific BERT variants (pre-trained with corpora from a particular background) have also achieved strong performance in many tasks. To our knowledge, previous machine learning studies of argument mining on judicial case law still heavily rely on statistical models. In this paper, we provide a broad study of both classic and contextual embedding models and their performance on practical case law from the European Court of Human Rights (ECHR). During our study, we also explore a number of neural networks when being combined with different embeddings. Our experiments provide a comprehensive overview of a variety of approaches to the legal argument mining task. We conclude that domain pre-trained transformer models have great potential in this area, although traditional embeddings can also achieve strong performance when combined with additional neural network layers.