The judge declared a mistrial after the jury received improper information.

mistrial 是由前缀 mis-（表示“错误、不当”）和名词 trial（“审判”）组成的复合名词，字面意思是“错误的审判”，在法律术语中指“无效审判”，即因程序错误或不当行为导致审判结果无效的情况。