'No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offence to be twice put in jeopardy of life or limb, nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use without just compensation.'
The Fifth Amendment 'can be asserted in any proceeding, civil or criminal, administrative or judicial, investigatory or adjudicatory; and it protects against any disclosures which the witness reasonably believes could be used in a criminal prosecution or could lead to other evidence that might be so used.' Kastigar v. U.S., 406 U.S. 441, 44-45 ('72). A reasonable belief that information concerning income or assets might be used to establish criminal failure to file a tax return can support a claim of Fifth Amendment privilege. See U.S. v. Rendahl, 746 F.2d 553, 55-56 (9th Cir.'84).
The only way the Fifth Amendment can be asserted as to testimony is on a question-by-question basis. Rendahl, 746 F.2d at 555, citing with approval U.S. v. Bell, 448 F.2d 40, 42 (9th Cir.'71) (Fifth Amendment challenge premature on appeal from enforcement order; appellant must present himself for questioning after enforcement and as to each question elect to raise or not to raise the defense).
The appropriate device for compelling answers to incriminating questions is a government grant of use immunity. See Sharp, 920 F.2d at 1172.