law: Indian Evidence Act, 1872 
  9. Facts necessary to explain or introduce relevant facts 
  Facts necessary to
  
  explain or introduce a fact in issue or relevant fact, or which support or
  
  rebut an inference suggested by a fact in issue or relevant fact, or which
  
  establish the identity of any thing or person whose identity is relevant, or
  
  fix the time or place at which any fact issue or relevant fact happened, or
  
  which show the relation of parties by whom any such fact was transacted, are
  
  relevant in so far as they are necessary for that purpose
  Illustrations
  (a) The question is,
  
  whether a given document is the will of A.
  The state of A’s
  
  property and of his family at the date of the alleged will may be relevant
  
  facts.
  (b) A sues B for a
  
  libel imputing disgraceful conduct to A; B affirms that the matter alleged to
  
  be libelous is true.
  The position and
  
  relations of the parties at the time when the libel was published may be
  
  relevant facts as introductory to the facts in issue.
  The particulars of a
  
  dispute between A and B about a matter unconnected with the alleged libel are
  
  irrelevant though the fact that there was a dispute may be relevant it is
  
  affected the relations between A and B.
  (c) A is accused of a
  
  crime.
  The fact that, soon
  
  after the commission of the crime, A absconded from his house, is relevant,
  
  under section 8 as conduct subsequent to and affected by facts in issue.
  The fact that at the
  
  time when he left home he had sudden and urgent business at the place to which
  
  he went is relevant, as tending to explain the fact that he left home suddenly.
  The details of the
  
  business on which he left are not relevant, except in so far as they are
  
  necessary to show that the business was sudden and urgent.
  (d) A sues B for
  
  inducing C to break a contract of service made by him with A.C,on leaving A’s service,
  
  says to A—"I am leaving you because B has made me a better offer" .
  
  This statement is a relevant fact as explanatory of Co’s conduct, which is
  
  relevant as a fact in issue.
  (e) A accused of
  
  theft, is seen to give the stolen property to B, who is seen to give it to A’s
  
  wife. B says as he delivers it—"A says your are to hide this". B’s
  
  statement is relevant as explanatory of a fact which is part of the
  
  transaction.
  (f) A is tried for a
  
  riot and is proved to have marched at the head of a mob. The cries of the mob
  
  are relevant as explanatory of the nature of the transaction.