Under the Indian Evidence Act, 1872, the general rule is that the burden of proof lies on the person who asserts a fact. However, Section 106 of the Act provides an important exception: "When any fact is especially within the knowledge of any person, the burden of proving that fact is upon him." Whether a person has a ticket for travelling on a train is a fact that is specifically within their personal knowledge. Therefore, if charged with travelling without a ticket, the burden of proving that they did possess a ticket rests upon the accused ('A' in this case).