In Arizona v.Youngblood 488 U.S. 51, (1988), police obtained semen samples from a rape kit and several items of clothing, but could not definitively establish the identity of the assailant through their initial tests. (Youngblood, supra, 488 U.S. at pp. 52-54.) The police subsequently failed to take measures necessary to preserve those samples, such as refrigerating the clothing. (Id. at p. 54.) Although properly preserved samples could have exculpated the defendant in that case, that evidence was only 'potentially useful' (id. at p. 58) to the defense and not '"potentially exculpatory"' at the time it was allowed to deteriorate (id. at pp. 57-58). The court held that 'unless a criminal defendant can show bad faith on the part of the police, failure to preserve potentially useful evidence does not constitute a denial of due process of law.' (Id. at p. 58.) The police obtained biological samples, which were initially only examined to determine whether sexual conduct had occurred. Later tests to narrow the pool of possible defendants were useless, and experts testified at trial about what "might have been shown" by tests performed more promptly or on better preserved samples. The trial court charged the jury that if it found the State had destroyed or lost evidence, they might infer that the evidence would have been against the State's interest, and the jury convicted the defendant of child molestation, sexual assault, and kidnapping. Id. at 53-54. The Supreme Court held that: (1) the possibility that the semen samples could have exculpated the defendants if preserved or tested is not enough to constitute "constitutional materiality"; and; (2) the exculpatory value of the evidence must be apparent before it was destroyed, which the defendant did not show here. Youngblood, supra, 488 U. S. at 56. The court continued: "The presence or absence of bad faith by the police for purposes of the Due Process Clause must necessarily turn on the police's knowledge of the exculpatory value of the evidence at the time it was lost or destroyed." Id. While good or bad faith is irrelevant if the State fails to disclose material exculpatory evidence, the court held, it is relevant when considering the State's failure to preserve evidence which only might have exonerated the defendant. Id. at 57. In summary, the court held that requiring a defendant to show bad faith on the part of the police both limits the extent of the police's obligation to preserve evidence to reasonable bounds and confines it to that class of cases where the interests of justice most clearly require it, i.e., those cases in which the police themselves by their conduct indicate that the evidence could form a basis for exonerating the defendant. We therefore hold that unless a criminal defendant can show bad faith on the part of the police, failure to preserve potentially useful evidence does not constitute a denial of due process of law. Id. at 58. In Arizona v.Youngblood, the issue was whether the State properly preserved semen samples of the perpetrator in a sexual molestation case. The State allegedly allowed the evidence to deteriorate before testing it, so the test results were inconclusive. The evidence was made available to the defendant, who declined to test it himself, and the State did not use the test results against the defendant at trial. Nevertheless, the defendant argued that if the State had properly preserved the evidence, it might have exonerated him. On these facts, the Court concluded that the exculpatory value of the semen evidence was not known to the State when the State allegedly mishandled it. Rather, "this evidence was simply an avenue of investigation that might have led in any number of directions." The evidence did not meet the standard announced in Trombetta because "no more can be said than that it could have been subjected to tests, the results of which might have exonerated the defendant." Id. at 57. Accordingly, the Court held that the State's failure to preserve evidence that is only "potentially useful" does not violate due process unless the defendant can show that the State acted in bad faith. The bad faith requirement avoids "imposing on the police an undifferentiated and absolute duty to retain and to preserve all material that might be of conceivable evidentiary significance in a particular prosecution." Id. The United States Supreme Court addressed the issue of whether a criminal defendant is denied due process of law by the State's failure to preserve evidence: "The Due Process Clause of the Fourteenth Amendment makes the good or bad faith of the State irrelevant when the State fails to disclose to the defendant material exculpatory evidence. But we think the Due Process Clause requires a different result when we deal with the failure of the State to preserve evidentiary material of which no more can be said than that it could have been subjected to tests, the results of which might have exonerated the defendant." Id. at 57-58, 109 S.Ct. 333, 102 L.Ed.2d 281. Thus, the Youngblood Court established two tests: one that applies when the evidence is "materially exculpatory" and one that applies when the evidence is "potentially useful." If the State fails to preserve evidence that is materially exculpatory, the defendant's rights have been violated. If, on the other hand, the State fails to preserve evidence that is potentially useful, the defendant's rights have been violated only upon a showing of bad faith. In Youngblood, the Supreme Court determined that the state's responsibility is further limited when the defendant's challenge is to "the failure of the State to preserve evidentiary material of which no more can be said than that it could have been subjected to tests, the results of which might have exonerated the defendant." (Arizona v. Youngblood (1988) 488 U.S. at p. 57.) In such a case, "unless a criminal defendant can show bad faith on the part of the police, failure to preserve potentially useful evidence does not constitute a denial of due process ...." (Id. at p. 58.) In Arizona v. Youngblood, the defendant sought reversal of his convictions because the State had failed to further test semen samples and had failed to refrigerate the victim's clothing so tests could be run on the semen deposited thereon, both in order to determine who the assailant was. The United States Supreme Court held, "Unless a . . . defendant can show bad faith on the part of the police, failure to preserve potentially useful evidence does not constitute a denial of due process." (Youngblood, supra, 488 U.S. at p. 58.) Bad faith can be established only by evidence produced by the defendant that the police knew that the items would exculpate him when they failed to conduct further tests and failed to refrigerate the clothing. ( Id. at pp. 56-57.) In determining that there was no showing of bad faith, the Supreme Court noted that the evidentiary items had been collected shortly after the crime and weeks before the defendant had been arrested. It further noted that the failure to test and refrigerate was, at worst, negligent. The Supreme Court said, "The presence or absence of bad faith by the police for purposes of the Due Process Clause must necessarily turn on the police's knowledge of the exculpatory value of the evidence at the time it was . . . destroyed." ( Youngblood, supra, 488 U.S. at pp. 56-57.) However, in the same footnote, the court also said, "The possibility that the semen samples could have exculpated respondent if preserved or tested is not enough to satisfy the standard of constitutional materiality in Trombetta." (Ibid.) In Youngblood, the court stated that the officers in question were acting in good faith, that the chances that the preserved samples would have exculpated the defendants were slim, and that the defendants had other means of demonstrating innocence. ( Youngblood, supra, 488 U.S. at p. 56.)