What is the effect of successfully asserting a defense or privilege to a battery or a trespass:

1. How far do the defenses and privileges go? That is, is the tortfeasor completely exonerated from any and all liability for the tort, or are there limitations?
2. And, what legal or social policies are served by allowing a tortfeasor to assert a defense or privilege?
3. Attribution to specific sources or materials in the text or elsewhere will enhance your essay.