P alleged that D had altered a semiautomatic rifle so it would discharge more than one shot per trigger pull--the defining characteristic of a machine gun. The rifle had indeed been modified in a way consistent with P's theory, though D's lawyer suggested it had been modified by its previous owner. P and D each had their own experts test-fire it. In P's test, the rifle did fire more than one shot per trigger pull, but when Ds expert (witnessed by two police officers) tested it, it didn't. D's expert suggested the gun may have fired automatically in P's test because of a malfunction, perhaps because the internal parts were dirty, worn or defective. P introduced a photograph of the rifle which, it argued, showed the rifle was neither dirty, worn nor defective. The photograph showed nothing of the gun's interior. All the jury could see was the outside, and not very well at that, as the gun occupied only a small part of the 4' X 6' photograph. The rest was taken up by about a dozen other weapons--nine other guns, including three that looked like assault rifles, and several knives--all belonging to D's housemate. D objected to admission of the photograph under Fed.R.Evid. 403, but the district court overruled his objection. D appealed his conviction.