the small quantity of cocaine involved in this case. The district court denied the motion, finding that the testimony would be helpful to a lay juror. The court then gave a cautionary instruction to the jury on the dual roles of a law enforcement officer as a fact witness and as an expert witness, see generally United States v. Lopes-Medina, 461 F.3d 724, 743-44 (6th Cir.2006), and defense counsel expressed satisfaction with the instruction. "Courts have overwhelmingly found police officers' expert testimony admissible where it will aid the jury's understanding of an area, such as drug dealing, not within the experience of the average juror." Lopez-Medina, 461 F.3d at 742 (citation and internal quotation marks omitted); see also United States v. Ham, 628 F.3d 801, 805 (6th Cir.2011) (<HOLDING>) (citation and internal quotation marks
holding that the evidence was sufficient to support a conviction under  856 where premises contained two white envelopes containing thirtytwo packs of crack cocaine equipment required for the manufacture and packaging of crack cocaine fortyone white envelopes containing particles of crack cocaine and crack cocaine stored in a laundry bag in the bathroom holding two prior convictions for distribution of crack relevant to show intent to distribute the crack found in defendants possession holding that the defendants prior distribution of crack was admissible to prove that he had intent and knowledge regarding crack found in a gym bag holding that district court did not err in determining that cocaine base was crack cocaine based on chemical analysis identifying cocaine base together with competent lay testimony bridging the evidentiary gap between cocaine base and crack cocaine and refusing to require showing of smokeability ie water solubility or melting point for purposes of establishing crack cocaine under the guidelines since smokeability distinguishes cocaine base from powder cocaine not from crack holding that a federal agents expert testimony regarding the characteristics of crack cocaine and the methods of its distribution was admissible and highly relevant in helping the jury resolve the central issue of whether the defendant possessed crack cocaine with intent to distribute