In United States v. Hassan El, 5 F.3d 726 (4th. Cir. 1993), police officers stopped a vehicle, in which the defendant was a passenger, for the driver's failure to stop at a stop sign. Id. at 728.
While at the vehicle, one of the officers observed that Hassan El appeared nervous and uncomfortable. The officer then noticed a bulge in the defendant's pants and asked him if he was carrying a gun. Hassan El, according to the police, grew visibly more uncomfortable by the question.
As the defendant appeared to be bringing his hands up toward the bulge, the officer grabbed the bulge through the window, revealing a loaded .38 caliber handgun. Id.
The Fourth Circuit held that this search did not violate the Fourth Amendment. Id. at 731.