The judge declared a mistrial because the jury couldn't agree on a verdict.

mistrial 是由前缀 mis-（表示"错误的"）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"，即因程序错误或陪审团无法达成一致而宣告无效的审判。