【1】 The criminal must be someone mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to follow.罪犯必须是故事开始时出现过的人,但不得是读者可以追踪其思想的人。
【4】 No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.作案时候,不能使用尚未发明的毒药,或需要进行深奥的科学解释的装置
【9】 The stupid friend of the detective, the Watson, must not conceal any thoughts which pass through his mind; his intelligence must be slightly, but very slightly, below that of the average reader.侦探的笨蛋朋友,比如华生,必须将其判断毫无保留地告诉读者,此人的智力须轻微低于读者的平均水平。