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.
(..) - Never? - No, sir. You got a Code Red 'cause your palms were sweaty. Why didn't Santiago, this burden to his unit, ever get one? Dawson wouldn't allow it, sir. Dawson wouldn't allow it. The guys talked tough about Santiago, but they wouldn't go near him. They were too afraid of Dawson. (..)1992 A Few Good Men