In Michigan v. Harvey, 494 U.S. 344 (1990), the United States Supreme Court addressed the use of illegally obtained evidence for the sole purpose of impeaching a testifying defendant: The prosecution must not be allowed to build its case against a criminal defendant with evidence acquired in contravention of constitutional guarantees and their corresponding judicially created protections. But use of statements so obtained for impeachment purposes is a different matter. If a defendant exercises his right to testify on his own behalf, he assumes a reciprocal "obligation to speak truthfully and accurately," Harris v. New York, 401 U.S. 222, 225; 91 S Ct 643; 28 L Ed 2d 1 (1971), and we have consistently rejected arguments that would allow a defendant to "'turn the illegal method by which evidence in the Government's possession was obtained to his own advantage, and provide himself with a shield against contradiction of his untruths.'" Id. at 224. The Supreme Court pointed out that it had "never prevented use by the prosecution of relevant voluntary statements by a defendant, particularly when the violations alleged by a defendant relate only to procedural safeguards that are 'not themselves rights protected by the Constitution' , but are instead measures designed to ensure that constitutional rights are protected." (Harvey, supra, 494 U.S. at p. 351.) As the Court explained: "the 'search for truth in a criminal case' outweighs the 'speculative possibility' that exclusion of evidence might deter future violations of rules not compelled directly by the Constitution in the first place. " (Harvey, supra, 494 U.S. at pp. 351-352.) The Supreme Court did not "consider the admissibility for impeachment purposes of a voluntary statement obtained in the absence of a knowing and voluntary waiver of the right to counsel." (Harvey, supra, 494 U.S. at p. 354.)