In Eccles v. Commonwealth, 214 Va. 20, 22, 197 S.E.2d 332, 333 (1973), the defendant was charged with selling marijuana. The trial court admitted evidence of the defendant's having been seen smoking marijuana on prior occasions in order to prove that he was familiar with marijuana and knew "what the contents of these bags might be or what the expedition was about." The Supreme Court, relying on Boyd, held that evidence of the defendant's prior drug use was inadmissible to prove the defendant knew that the substance he possessed was marijuana. The fact that Eccles had previously used marijuana and had knowledge of the nature and character of marijuana was unrelated to the charged offense and did not tend to prove that Eccles knew that the substance in the bag was marijuana or that a sale of marijuana was being made. The Court reversed the defendant's conviction and remanded, stating "since we have no way of knowing the effect of the court's admission of testimony as to defendant's prior criminal acts of smoking marijuana had upon the minds of the jury, we cannot say that the error was not prejudicial." Eccles, 214 Va. at 22-23, 197 S.E.2d at 333.