The 'burden of proof' is on the plaintiff, since the defendant is presumed innocent until proven guilty. [=the plaintiff must prove that the defendant is guilty]
The 'tax burden' has been falling increasingly on the middle class. [=middle class people have been paying a greater portion of taxes]
For the rest of his life he 'was burdened' with the knowledge that he had done nothing to help them.
(..) I just think he's guilty. I thought it was obvious from the word go. Nobody proved otherwise. Nobody has to prove otherwise. The burden of proof's on the prosecution. The defendant doesn't even have to open his mouth. That's in the Constitution. Sure, I know that. What I meant was... (..)1957 12 Angry Men