Edit: See https://en.wikipedia.org/wiki/Haynes_v._United_States for NFA. Thanks below for Leary.
Edit: See https://en.wikipedia.org/wiki/Haynes_v._United_States for NFA. Thanks below for Leary.
I think the 5th has been restricted enough by the courts that it literally only matters if you EXPLICITLY invoke it. (At least this is my understanding of Berghuis v. Thompkins.)
Similar for the NFA case - they can't get then for the failure to register, but they can still get them for manufacturing/possessing it (especially since it was amended after the ruling).
>they can't get then for the failure to register
A criminal filing an 8300 would be effectively "registering" their illegally owned money, including the source from who the money is received.
"and that you couldn't pay that tax without registering"
The form 8300 actually requires you to state both counterparties of the illegal transaction, which goes well within furnishing evidence useful in incriminating yourself. It's far more incriminating than the annual tax return, which shows an aggregate yearly amount rather than granularity of single transaction (or collection of "associated"-transaction) along with the date and name of both counterparties and a host of other details.