law: Indian Evidence Act, 1872 
  46. Facts bearing upon opinions of experts 
  Facts, not otherwise
  
  relevant, are relevant if they support or are inconsistent with the opinions of
  
  experts, when such opinions are relevant.
  Illustrations
  (a) The question is,
  
  whether A was poisoned by a certain poison.
  The fact that other
  
  persons, who were poisoned by that poison, exhibited certain symptoms which experts
  
  affirm or deny to be symptoms of that poison, is relevant.
  (b) The question is,
  
  whether an obstruction to a harbor is caused by a certain sea-wall.
  The fact that other
  
  harbors similarly situated in other respects, but where there were no such sea-walls,
  
  began to be obstructed at about the same time, is relevant.