You can be jailed without a witness or charges.
Under the 5th amendment, all US citizens SHOULD have a right to know their crime and what they are being charged with. Furthermore, the government should be unable to detain US citizens without any charges. As of the Ashcroft raid which occurred shortly after the September 11 attacks, this appears to be no longer the case. Hundreds of Arab, Muslim, and South-Asian men, including American citizens, were rounded up and held indefinitely, with no clear appeals process for their release, until after they had all been cleared of being potential terrorists. This is also a clear violation of the 6th amendment, the right to a public and speedy trial.