United States v. Rios, __ F.3d __ (9th Cir. Jun. 02, 2006) (expert testimony that drug traffickers generally use firearms to further their drug crimes, was not by itself sufficient to establish that a firearm was possessed in furtherance of a particular drug crime).
http://caselaw.lp.findlaw.com/data2/circs/9th/0550000p.pdf