In what circumstances have courts found that the delay between the indictment and trial of a defendant on drug charges violated his Sixth Amendment rights?

In United States v. Jeanetta, 533 F.3d 651 (8th Cir. 2008), the court rejected a defendant's claim that the fifteen-month delay between his indictment on drug charges and trial had violated his Sixth Amendment rights. Id. at 656-57. Eight months after his indictment, the defendant was found and arrested. Two handguns were seized during that arrest. Weeks before his trial, a superseding indictment added firearms charges to the drug charges. Id. at 653-54.