WordNet sense 1 (any evidence that helps to establish the falsity of something):

disproof, refutation

WordNet sense 2 (a willful perversion of facts):

misrepresentaation

WordNet sense 3 (the act of rendering something false as by fraudulent changes (of documents or measures etc.) or counterfeiting):

falsehood

WordNet sense 4 (the act of determining that something is false):

falsifying, refutal