D could also counterclaim alleged P to be responsible for D's injuries as well. If a party fails to assert a mechanical malfunction, it will not be waived because Rule 15 allows amendments to the pleadings. Rule 15 you can amend fairly liberally when justice so requires, unless it is in bad faith. In this case a mechanical malfunction would be required in the complaint for justice to occur. D Paul can determine whether Doe's contributory negligence is an affirmative defense under the substantive state law.
Contributory negligence is listed as an aff.
If Doe calls contributory negligence an affirmative defense P will only have to reply if the court orders him to reply. They also must give any insurance agreements or experts who will testify at trial. B Number 1 is outside the scope of discovery because it is not relevant to the case. His injuries to past accidents do not pertain to his injuries from this accident, and also it does not appear to be reasonably calculated to lead the discovery of admissible evidence. Number 2 would be privileged under the attorney-client relationship.