It is not rational to presume beyond a reasonable doubt that a defendant knew that just because one drug gives similar effects as another, the two drugs share similar chemical structures.
United States v. Makkar, 2015 BL 384626, 10th Cir., No. 14-5147, 11/23/15
The 10th Circuit Court of Appeals overturned the convictions of two men selling controlled substance analogues. The convictions were reversed because the trial court jury had been instructed to infer that because the drug's effects were similar to marijuana, the men knew that it was an illegal drug.
The court said that "[a]s a matter of common experience and logic, the fact that one drug produces a similar effect to a second drug just doesn't give rise to a rational inference-let alone rationally suggest beyond a reasonable doubt-that the first drug shares a similar chemical structure with the second drug."
The convictions followed a method of proving mens rea given in McFadden v. United States (U.S. 2015). In that case, and this one, mens rea was proven by showing that the defendants knew the analogue had a similar chemical structure to the illegal drug and produced a similar effect. Those are two separate questions.
In this case the government never showed that the defendant's knew anything about the chemical structure. Instead they had the jury instructed to infer that the defendants knew the structure was similar based on what they knew the effects to be. This conflated two independent statutory inquiries, and did so by "resorting to a logical fallacy, a hasty generalization or associational error-an unwarranted assumption that because certain things share one characteristic they must share others."