'Transactional immunity . . . provides the individual with an assurance that he is not testifying about matters for which he may later be prosecuted. No question arises of tracing the use or non-use of information gleaned from the witness' compelled testimony. The sole question presented to a court is whether the subsequent prosecution is related to the substance of the compelled testimony. Both witness and government know precisely where they stand. Respect for law is furthered when the individual knows his position and is not left suspicious that a later prosecution was actually the fruit of his compelled testimony.' 400 U.S. at 400 U. S. 568-569 (dissenting).
When courts allow the prosecution to offer only 'use' immunity, they allow a grant far less than it has taken away. For while the precise testimony that is compelled may not be used, leads from that testimony may be pursued and used to convict the witness.
In Counselman v. Hitchcock, 142 U. S. 547, 142 U. S. 586, the Court adopted the transactional immunity test: 'In view of the constitutional provision, a statutory enactment, to be valid, must afford absolute immunity against future prosecution for the offense ...