Burden of proof is a tool and term used in law used to define who is the person responsible for sustaining a claim or concept. The term specifies that the person responsible for a given claim is also the one who must provide the necessary evidence to support it.
The burden of proof assumes that every statement needs support, evidence to be taken into account, and when they are not offered, this statement has no argumentative value and should be disregarded in reasoning logical. The problem of the burden of proof arises when trying to define who has the burden of proof, and this is when many people get confused. The risk here is to place the burden on the wrong person, thus reversing the logic of reasoning and destroying its support.
Generally, the burden of proof always rests on the primordial claim, the basis of all logical reasoning, and as long as that claim is not proven, all reasoning must be disregarded.
According to the Code of Civil Procedure, the burden of proof is the burden assigned by law to each of the parties of a process, of demonstrating the occurrence of the facts of its own interest for the decisions to be uttered. The burden of proof is on the plaintiff, as to his right, and the defendant, as to the existence of an impeding, modifying or extinguishing fact of the plaintiff's right.
See also the meaning of Reversal of the burden of proof and Low sufficiency.