No. of Recommendations: 1
It's not privileged - that was shot down in U.S. v. Nixon. It's inarguable that it can be used in the criminal prosecution of everyone else involved in the murder conspiracy (none of whom have immunity), which means that it can be obtained by investigators. And nothing in the opinion says it can't be used in the judge's determination of whether or not the underlying acts are immune acts or not. In fact, the opinion specifically allows the government to rebut the presumption that the actions are not within the scope of immunity, which requires that the government be allowed to use the evidence to make that showing. The evidence can't be used at trial to support other charges, because that would erode the protections of immunity - but allowing it to be used to determine whether an action is or is not entitled to immunity doesn't implicate that concern.
Aaah, I missed this, this helps quite a bit.