discussed Cited "see" Cothran v. Turner See Duckett v. Mullin, 306 F.3d 982, 998 (10th Cir.2002) (“It would be unreasonable to deem trial counsel ineffective for failing to discover potential mitigating evidence when counsel conducted a reasonable investigation but was stymied by potential witnesses who were not forthcoming.”), cert. denied, 538 U.S. 1004 , 123 S.Ct. 1911 , 155 L.Ed.2d 834 (2003).