material witness
A witness who can testify about matters having some logical connection with the consequential facts, esp. if few others, if any, know about those matters. [Cases: Witnesses 4.]
material witness
重要证人
重要证人 英语：material witness 法语：témoin essentiel 德语：wichtiger Zeuge 意大利语：testimone essenziale 西班牙语：testigo importante, testigo clave