I suspect that the interlopers and usurpers have gotten desperate so they have resorted to those sorts of games. They intentionally set out to seize the office without the oath (deception in war?) and so anyone interacting with them has the potential to become ensnared in conflict of laws / private international law: a parallel universe that collapses when quit. Consider Agenda 21, TIP, all executive agreements, the PM of the UK having signed an agreement to enter the EU without support of the People of the UK: limited territorially, non-binding unless you enter into the fuzzy jurisdiction.
Grand Jury
Yes a true Grand Jury need not be one formed under statute or under color of law--that is, I'm unaware of any mandatory requirement. If you form it under the state court then there are the rules. The people can without statute establish boards, councils, committees, commission or the like for inquiries, investigations, etc. Also, the people or anyone can issue a writs of mandamus generally on all officers of a state or county or the mayor of a city to **demand*** or to **require** all the officers of any given state to remain intra vires or to faithfully perform their duties.
Any such board, council, committee, commission or the like could still be utilize the USDC as an evidence repository ala libel of review (parallel case).
Grand Jury or Board As Mini-Electorate
Consider, if you will, most any grand jury or the like as a mini-electorate that can be full of municipal corporate persons or not just like the county of denver could fill to the brim with the city of Denver or not. If its filled with the attorned, its no surprise if the attorney wields all of the power. Clearly they are consciously aware of this. Hmm if police officers are agents of the attorney, would it be any surprise he or she would set out to thwart evidence of liability at all costs (principal is liable for his agents).
P.S. Could "DAVID A GILBERT" be a title of nobility rather than any name?