The witness is going to lead the jury to a blind alley.
这个证人将把陪审团引入死胡同。
解析:a blind alley字面上的意思就是只有一个出入口的小路,引申出死胡同,行不通等含义。英语中的意思为a street with only one way in or out,比喻a course of action that is unproductive and offers no hope of improvement.
解析:to keep up appearances的意思是故作镇定,摆谱儿。英语含义为to pretend that everything in your life is normal and happy even though you are in trouble, especially financial trouble.