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.
(..) was king of Rohan. Then what is the king's decision? ... ...the city must empty. We make for the refuge of Helm's Deep. Do not burden yourself with treasures. Take only what provisions you need. Helm's Deep. They flee to the mountains when they should stand and fight. (..)2002 The Lord of the Rings: The Two Towers