A more thorough explanation:

The missing-witness rule is a legal principle that allows a jury to infer that a witness's testimony would have been unfavorable to a party who fails to present that witness at trial. This rule applies when a party has exclusive control over a witness who could provide relevant testimony but fails to call that witness to the stand.

Suppose a car accident case goes to trial, and the plaintiff claims that the defendant ran a red light and caused the accident. The defendant argues that the plaintiff was driving recklessly and caused the accident. The plaintiff has a witness who was in the car with them at the time of the accident, but the plaintiff fails to call that witness to testify. The missing-witness rule allows the jury to infer that the witness's testimony would have been unfavorable to the plaintiff's case.

Another example could be a criminal case where the prosecution fails to call a witness who was present at the scene of the crime and could provide crucial evidence. In such a case, the missing-witness rule would allow the jury to infer that the witness's testimony would have been unfavorable to the prosecution's case.

These examples illustrate how the missing-witness rule works in practice. It is important to note that the rule only applies when a party has exclusive control over a witness who could provide relevant testimony. If the witness is equally available to both parties, the rule does not apply.