What is the test for overturning a conviction where evidence has been lost or destroyed?

3 We think this test is consistent with the result in United States v. Heiden, 508 F.2d 898 (9th Cir. 1974). Heiden states that where evidence has been lost or destroyed the conviction will be reversed if the defendant can show "(1) bad faith or connivance on the part of the Government, or (2) that he was prejudiced by the loss of the evidence." As the discussion in Heiden demonstrates, "prejudice" as used there means serious impairment of the accused's ability to present his defense. In cases of severe prejudice the Heiden formulation would lead to the same result as under the test set forth in this case.