with whom Mr. Justice Rehnquist joins, concurring.
I concur in the Court’s opinion, and add these comments.
As stated by the Court, New Jersey makes two arguments in support of its request for reversal. First, it insists that, because Portash did not take the witness stand, his immunized testimony was not used against him and he therefore cannot complain of a violation of his Fifth Amendment privilege. The preferred method for raising claims such as Portash’s would be for the defendant to take the stand and appeal a subsequent conviction, if — following a claim of immunity — the prosecutor were allowed to use immunized testimony for impeachment. Only in this way may the claim be presented to a reviewing court in a concrete factual context. Moreover, requiring that the claim be presented only by those who have taken the stand will prevent defendants with no real intention of testifying from creating artificial constitutional challenges to their convictions.1
This is a state case, however, in which the New Jersey Appellate Division apparently accepted the procedure followed by the trial court and treated the constitutional question as having been properly presented. I agree with the Court that this procedural question was within the authority of the state court to decide.2
*463The State also argues, quite apart from the procedural context in which the question arises, that immunized grand jury testimony may be used to impeach a criminal defendant’s testimony at trial. The Court correctly rejects this argument, ruling that the coercing of Portash to testify before the grand jury constituted a classic case of “compelling” a defendant to be a witness against himself. See Kastigar v. United States, 406 U. S. 441, 453 (1972).
The Court has referred to two quite different interests in determining whether the Fifth Amendment permits a defendant’s statements to be used against him at trial. In Harris v. New York, 401 U. S. 222 (1971), the Court emphasized the trustworthiness of a suspect’s statements made to police, noting that there was no indication that the statements were “coerced or involuntary.” Similarly, here there is no reason to question the veracity of the respondent’s grand jury testimony. The Court today recognizes, however, that the privilege against self-incrimination protects against more than just the use of false or inaccurate statements against a criminal defendant. In addition, the Fifth Amendment, by virtue of its incorporation through the Fourteenth Amendment, prohibits a State from using compulsion to extract truthful information from a defendant, when that information is to be used later in obtaining the individual’s conviction.
Criminal defendants, as an aid to determining trial strategy, no doubt would prefer to be told in advance of trial whether prior testimony may be used to impeach if they take the stand. But there is no constitutional requirement that defendants be given such a ruling at a time when only a hypothetical question can be presented.
Accordingly, the Court need not, and, as I read its opinion, does not *463decide whether it would regard the constitutional issue as having been properly presented if this case had arisen in federal court.