STONE, Judge.
The admission of rebuttal testimony by the arresting officer, concerning his experience with common drug courier practices, was irrelevant to any of the substantive issues in this case. Additionally, it was not within the scope of cross examination, nor was it introduced as background to explain the officer's conduct. See United States v. Hernandez-Cuartas, 717 F.2d 552 (11th Cir.), reh'g denied, 721 F.2d 822 (11th Cir. 1983). The error in this case was not harmless.
The judgment and sentence are, therefore, reversed and the case remanded for further proceedings.
DOWNEY and LETTS, JJ., concur.