Is evidence of prior drug use admissible in a prosecution for possession with intent to distribute?

Evidence of prior drug use is inadmissible in a prosecution for possession with intent to distribute. United States v. Mehrmanesh, 689 F.2d 822, 831-32 (9th Cir.1982). Evidence of prior possession, however, is admissible. Id. at 832; United States v. Brown, 562 F.2d 1144, 1147-48 (9th Cir.1977). While the distinction may be thin, it is dispositive. If evidence of prior possession may be admitted into evidence despite its prejudicial effect, evidence of contemporaneous possession, tending to show the defendant's knowledge of drugs and the unlikelihood that he possessed the drugs accidently, can hardly be excluded.