Used to be a time when you couldn’t do this (develop negative evidence). Oh, the times they are a changin’. Guess we know where this one is heading.

Further, with respect to risk factors, the VA examiner must consider the Veteran’s exposure to such during service, to include a possible association between the Veteran’s in-service diagnosis of hepatitis and drug use noted in the aforementioned service treatment record. In this regard, VA has an affirmative duty to gather the evidence necessary to render an informed decision on a claim, even if that means gathering and developing negative evidence. Douglas v. Shinseki, 23 Vet. App. 19 (2009).

Here’s Douglas.  Click on download to view normally. So much for nonadversarial, friendly Barney the Dinosaur VA.