I wonder about the fruit of the poisonous tree in this case, though. IANAL, so I am honestly curious if this doctrine applies to civil proceedings. Secondly,

I wonder about the fruit of the poisonous tree in this case, though. IANAL, so I am honestly curious if this doctrine applies to civil proceedings. Secondly, the tax offices presumably have a right to carry out audits and don't need to substantiate why. I would think that they could use any method ranging from a dice roll to an anonymous tip on a hotline to trigger an audit. The trigger would not be used as evidence in the trial... it may be from a jealous lover who's lying, but if the audit reveals you didn't pay your taxes properly, well there you go. Thirdly, it may not even matter. Saying 'we have this material' is a great bluff on it's own and could be used to get rule breakers to come clean on their own, as well as sending a message to would-be tax dodgers that it's getting harder and harder to cover your tracks. This doesn't say anything about the moral issue of tacitly condoning stealing documents by paying for them, though.