  Given a specific query case, legal case retrieval systems aim to retrieve a
set of case documents relevant to the case at hand. Previous studies on user
behavior analysis have shown that information retrieval (IR) systems can
significantly influence users' decisions by presenting results in varying
orders and formats. However, whether such influence exists in legal case
retrieval remains largely unknown. This study presents the first investigation
into the influence of legal case retrieval systems on the decision-making
process of legal users. We conducted an online user study involving more than
ninety participants, and our findings suggest that the result distribution of
legal case retrieval systems indeed affect users' judgements on the sentences
in cases. Notably, when users are presented with biased results that involve
harsher sentences, they tend to impose harsher sentences on the current case as
well. This research highlights the importance of optimizing the unbiasedness of
legal case retrieval systems.
