What is the state's responsibility to preserve or preserve evidence in a criminal case?

[the evidence] possesses exculpatory value 'apparent before [it] was destroyed,' and not obtainable 'by other reasonably available means.' " (People v. DePriest (2007) 42 Cal.4th 1, 41 (DePriest).) The state's responsibility is further limited when the defendant challenges the failure to preserve evidence " 'of which no more can be said than that it could have been subjected to tests' " that might have helped the defense. (Arizona v. Youngblood (1988) 488 U.S. 51, 57 (Youngblood).)