Welcome to my favourite OS X bugbear. I defy you to permanently delete some files without deleting others in the trash, or emptying the trash on a removable drive without emptying everything else along with it. I am sure it can be done via the command line, or with some third-party app, but for us mere mortals or people who expect it "to just work", there's no way that I can see.
Of course, I'm open to suggestions. 😉