What is burden of proof? On whom the burden of proof lies in a suit or proceedings?

Our judicial system is based on evidence. The conclusion of court depends upon the proof. The burden of proof keeps on changing with the circumstances of the case, thereby increases the importance of burden of proof. 

What is burden of proof? 

Generally, burden of proof means- the burden on any party to prove any particular fact. 
The principle of Burden of proof is based on the concept of onus probandi (burden of proof) and factum probans (proving a fact). While the burden of proof remains constant, the onus for the same shifts from one party to another.

Section 101 of Indian Evidence Act, 1872 propounds the general principal regarding burden of proof. 
From the point of view of the burden of proof, the facts can be placed in two categories: those which affirm a fact and those which deny it. According to section 101 of the Indian Evidence act 1872, the party who asserts the affirmative of an issue, to make the court give a judgment on the basis of those facts, carries the burden of proof to prove them; it is easier to prove the affirmative than the negative. The affirmative in issue should not be in form or grammar but in substance. 

Illustration - 
(a) A desires a court to give judgement that b shall be punished for a crime which A says B has committed. A must prove that B has committed the crime. 
In the simplest words, it can be said that – burden of proof means the liability or binding of a person to prove any fact. Generally this liability lies over the person who makes a statement and expects the court to decide according to it. 

In the case of Daulatram VS Sodha it was held by Supreme Court that if any person says that the will is made by fraud, undue influence or coercion then the burden of proof shall be on that person. 

Burden of proof is briefly describe from section 102 to Section 112 
1 On whom burden of proof lies 

Section 102. On whom burden of proof lies.—The burden of proof in a suit or proceeding lies on that person who would fail if no evidence at all were given on either side. Illustrations
(a) A sues B for land of which B is in possession, and which, as A asserts, was left to A by the will of C, B’s father. If no evidence were given on either side, B would be entitled to retain his possession. Therefore the burden of proof is on A.
(b) A sues B for money due on a bond. The execution of the bond is admitted, but B says that it was obtained by fraud, which A denies. If no evidence were given on either side, A would succeed, as the bond is not disputed and the fraud is not proved. Therefore the burden of proof is on B.

2 Burden of Proof as to particular fact section 103 
 Burden of proof as to particular fact.—The burden of proof as to any particular fact lies on that person who wishes the Court to believe in its existence, unless it is provided by any law that the proof of that fact shall lie on any particular person.
3 Burden of proving fact to be proved to make evidence admissible Section 104 
The burden of proving any fact necessary to be proved in order to enable any person to give evidence of any other fact is on the person who wishes to give such evidence. Illustrations
(a) A wishes to prove a dying declaration by B. A must prove B’s death.
(b) A wishes to prove, by secondary evidence, the contents of a lost document. A must prove that the document has been lost.

4 Burden of proving that the case comes within exception 
Section 105 in The Indian Evidence Act, 1872
When a person is accused of any offence, the burden of proving the existence of circumstances bringing the case within any of the General Exceptions in the Indian Penal Code, (45 of 1860), or within any special exception or proviso contained in any other part of the same Code, or in any law defining the offence, is upon him, and the Court shall presume the absence of such circumstances.

Illustrations
(a) A, accused of murder, alleges that, by reason of unsoundness of mind, he did not know the nature of the act. The burden of proof is on A.
(b) A, accused of murder, alleges, that by grave and sudden provocation, he was deprived of the power of self-control. The burden of proof is on A.

Section 106 - Burden of proving fact especially within knowledge

When any fact is especially within the knowledge of any person, the burden of proving that fact is upon him.

Illustrations
(a) When a person does an act with some intention other than that which the character and circumstances of the act suggest, the burden of proving that intention is upon him.
(b) A is charged with travelling on a railway without a ticket. The burden of proving that he had a ticket is on him

Section 107 Burden of proving death of person known to have been alive within thirty years.—When the question is whether a man is alive or dead, and it is shown that he was alive within thirty years, the burden of proving that he is dead is on the person who affirms it.

Section 108 of Evidence Act "Burden of proving that person is alive who has not been heard of for seven years"
Provided that when the question is whether a man is alive or dead, and it is proved that he has not been heard of for seven years by those who would naturally have heard of him if he had been alive, the burden of proving that he is alive is [shifted to] the person who affirms it .

Section 109 of the Indian Evidence Act, 1872
Burden of proof as to relationship in the cases of partners, landlord and tenant, principal and agent:
When the question is whether persons are partners, landlord and tenant, or principal and agent, and it has been shown that they have been acting as such, the burden of proving that they do not stand, or have ceased to stand, to each other in those relationships respectively, is on the person who affirms it.

Section 110. Burden of proof as to ownership.—When the question is whether any person is owner of anything of which he is shown to be in possession, the burden of proving that he is not the owner is on the person who affirms that he is not the owner.

Section 111. Proof of good faith in transactions where one party is in relation of active confidence.—Where there is a question as to the good faith of a transaction between parties, one of whom stands to the other in a position of active confidence, the burden of proving the good faith of the transaction is on the party who is in a position of active confidence.

Illustrations
(a) The good faith of a sale by a client to an attorney is in question in a suit brought by the client. The burden of proving the good faith of the transaction is on the attorney.
(b) The good faith of a sale by a son just come of age to a father is in question in a suit brought by the son. The burden of proving the good faith of the transaction is on the father.