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.
(..) It can be a hard place. I don't know why I asked you to come. Why don't you talk to him about it? Tell him how you feel. I can't. You know, I can't be a burden. Especially now. I'll get used to things... you know? I wanted to talk to someone... who's lived here for a long time. (..)1995 Se7en