Case of First Impression

Definition from Nolo’s Plain-English Law Dictionary

A court case that presents a new question or issue for legal interpretation (or at least new within that court's jurisdiction). For example, the question may concern recently passed or rarely used legislation. In making its decision, the court may consider -- but is not bound by -- decisions from other state or federal courts or commentaries by legal scholars, as well as the arguments and briefs submitted by lawyers in the case.

Definition provided by Nolo’s Plain-English Law Dictionary.