Burden of proof and shifting onus: burden generally stays while onus may shift as evidence changes parties' obligations. Distinction between Burden of Proof and Onus of Proof: burden remains with the party who asserts a fact while onus may shift as evidence alters probabilities; in title-based possession suits a plaintiff may shift onus to the defendant to rebut. Under the Evidence Act the burden to prove a fact for which a party seeks the court's belief rests on that party, and the burden to prove foundational facts for admitting other evidence rests on the party offering it. In insurance law the insurer must prove non-disclosure and fraudulent intent to exclude liability.