What is the current state of the law on police destruction of evidence in criminal cases?

The Constitution places a duty on police to preserve certain evidence. This duty is limited to "evidence that might be expected to play a significant role in the suspect's defense." California v. Trombetta, 467 U.S. 479, 488 (1984). This evidence must "possess an exculpatory value that was apparent before the evidence was destroyed, and be of such a nature that the defendant would be unable to obtain comparable evidence by other reasonably available means." Id. at 489. Even if the evidence meets these requirements, however, due process will only be violated when the police act in bad faith. Arizona v. Youngblood, 488 U.S. 51, 58 (1988). In addition, the duty extends only to the preservation of evidence; there is no duty on the police to obtain exculpatory evidence. Miller v. Vasquez, 868 F.2d 1116, 1119 (9th Cir.1989).