A more thorough explanation:

A special interrogatory is a written question that is submitted to the opposing party in a lawsuit as part of the discovery process. It is usually included in a set of questions and is used to gather information about the case.

For example, in a personal injury case, the plaintiff's attorney may submit a special interrogatory to the defendant asking for details about the accident, such as the speed of the vehicles involved and the weather conditions at the time of the accident. The defendant must answer the question in writing and under oath.

Another type of special interrogatory is a written jury question that requires an answer to supplement a general verdict. This type of special interrogatory is not used in federal practice, but it is used in some state courts. For example, in a medical malpractice case, the jury may be asked a special interrogatory about whether the defendant doctor breached the standard of care. The answer to this question would supplement the general verdict and help the judge determine the outcome of the case.