How to instruct a jury in a drug case that a defendant intentionally avoided learning all the facts in order to avoid prosecution?

The instruction is not given in all cases, however, because of the possibility that the jury will be led to employ a negligence standard and convict the defendant on the impermissible ground that he should have known a drug transaction was taking place. United States v. Garzon, 688 F.2d 607, 609 (9th Cir.1982). Accordingly, the instruction should be given only if there is evidence that the defendant purposely contrived to avoid learning all the facts in order to have a defense in the event he was arrested and charged. Id.