How have courts interpreted "bad faith" in failing to preserve or preserve "potentially useful evidence"?

However, to protect the courts from the "treacherous task of divining the import of materials whose contents are unknown, " unless a criminal defendant can show bad faith on the part of law enforcement, "failure to preserve potentially useful evidence does not constitute a denial of due process." Arizona v. Youngblood, 488 U.S. 51, 58, 109 S.Ct. 333 (1988). "Bad faith" consists of official animus towards [the accused] or a conscious effort to suppress exculpatory evidence."

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