How have the rules of voir dire been interpreted in the context of drug possession cases?

Previous cases provide clear examples of the application of these rules. In Baldwin, the trial court refused to ask two questions: whether the venire knew the prosecution's witness; and whether they would be unduly swayed by the testimony of a law enforcement officer. The prosecution's case relied primarily on the testimony of two agriculture agents. This court reversed the conviction because the voir dire was inadequate. This court affirmed a conviction in United States v. Powell, 932 F.2d 1337 (9th Cir.1991). There, the defendant was convicted of possessing cocaine with intent to distribute. On voir dire, the court refused to ask whether the venire would be influenced by the testimony of a law enforcement officer. As the case included corroborating evidence of drug related items and congruent testimony from other witnesses, this court affirmed the conviction.