Which of the following is a valid defense that must be raised in the answer?

The valid defense that must be raised in the answer is collateral estoppel. This legal doctrine prevents a party from relitigating an issue that has already been determined in a final judgment in a previous case. When a party has been previously involved in a legal matter and the court has made a definitive ruling regarding particular facts or issues, that ruling can be used as a defense in subsequent litigation involving the same parties or their privies.

By asserting collateral estoppel in the answer, the defendant establishes that the issue at hand has already been conclusively decided, which can lead to a dismissal of the claims due to the inability to relitigate the determined issue. This aligns with the principles of judicial economy and finality of judgments, thereby promoting efficient legal processes.

Other options listed, such as jurisdiction errors, pleading for the privilege, and lack of personal knowledge, generally do not constitute defenses that must be raised in the answer in the same manner as collateral estoppel. Jurisdictional issues may often be raised at any stage of the proceedings because they can impact the court’s ability to hear a case. Pleading for the privilege typically relates to specific defenses involving an assertion of a legal right, safeguarding against liability based on circumstances that do not need to be