law: Indian Evidence Act, 1872 
  7. Facts which are the occasion, cause or effect of facts
  
  in issue
  Facts which are the
  
  occasion, cause, or effect, immediately or otherwise, of relevant facts, or
  
  facts in issue, or which constitute the state of things under which they
  
  happened, or which afforded an opportunity for their occurrence or transaction,
  
  are relevant.
  Illustrations
  (a) The question is,
  
  whether A robbed B.
  The facts that,
  
  shortly before the robbery, B went to a fair with money in his possession, and
  
  that he showed it or mentioned the fact that he had it, to third persons, are
  
  relevant.
  (b) The question is
  
  whether A murdered B.
  Marks on the ground,
  
  produced by a struggle at or near the place where the murder was committed, are
  
  relevant facts.
  (c) The question is
  
  whether A Poisoned B.
  The state of B’s
  
  health before the symptoms ascribed to poison, and habits of B, known to A,
  
  which afforded an opportunity for the administration of poison, are relevant
  
  facts.