Unring the bell
（重定向自Unring）
In law, unring the bell is an analogy used to suggest the difficulty of forgetting information once it is known. When discussing jury trials, the phrase is sometimes used to describe the judge's instructions to the jury to ignore inadmissible evidence or statements they have heard. It may also be used if inadmissible evidence has been brought before a jury and the judge subsequently declares a mistrial.