In Harris v. New York, 401 U.S. 222 (1971), the United States Supreme Court ruled that trustworthy custodial statements made without prior Miranda warnings were admissible to impeach a defendant, if accompanied by an appropriate jury instruction, but not as evidence of guilt. The opinion notes that it is one thing to say that the government cannot make an affirmative use of evidence unlawfully obtained, but "quite another to say that the defendant can turn the illegal method by which evidence . . . was obtained to his own advantage, and provide himself with a shield against contradiction of his untruths." (401 U.S. at p. 224.) "Assuming that the exclusionary rule has a deterrent effect on proscribed police conduct, sufficient deterrence flows when the evidence in question is made unavailable to the prosecution in its case in chief. "Every criminal defendant is privileged to testify in his own defense, or to refuse to do so. But that privilege cannot be construed to include the right to commit perjury. Having voluntarily taken the stand, petitioner was under an obligation to speak truthfully and accurately, and the prosecution here did no more than utilize the traditional truth-testing devices of the adversary process." (401 U.S. at p. 225.) "The shield provided by Miranda cannot be perverted into a license to use perjury by way of a defense, free from the risk of confrontation with prior inconsistent utterances." (401 U.S. at p. 226.) The United States Supreme Court created an exception to the general rule of Miranda--namely, that while a statement taken without proper Miranda advisements is inadmissible in the prosecution's case-in-chief, it may be admitted for impeachment purposes. (Accord, People v. May, supra, 44 Cal.3d 309, 315.) Harris teaches that if a defendant elects to testify in his own defense, he or she is obligated to testify truthfully and will not be permitted to use the illegal method by which the prosecution obtained incriminating evidence to commit perjury. (Harris, at pp. 225-226.) "The shield provided by Miranda cannot be perverted into a license to use perjury by way of a defense, free from the risk of confrontation with prior inconsistent utterances." (Id. at p. 226.)