How has the doctrine of Feres been interpreted in medical malpractice cases?

We start with the recognition, as did the district court, that not every action by one member of the armed services against another implicates military decision making, relates to the military mission, or is incident to service. Here three subordinates had a personal vendetta against a superior. They broke into her office after hours, opened her private mail, and disseminated it in an attempt to ruin her reputation. It seems hardly possible that this conduct or the resulting injury to the victim "arises out of or is incident to service." The district court found it did not. However, in light of the recent tendency to apply Feres broadly, we are presented with a closer question than is apparent at first blush. As we noted in Persons v. United States, 925 F.2d 292 (9th Cir.1991) (applying Feres to a medical malpractice case):