Those facts which must be proved by the party making an allegation in order to succeed and the facts that the defendant must prove in order to establish his defence.
The expression “facts in issue” means and includes- any fact from which, either by itself or in connection with other facts, the existence, non-existence, nature or extent of any right, liability, or disability, asserted or denied in any suit or proceeding, necessarily follows. ….. [Section 3 of the Evidence Act, 1872]