law: Indian Divorce Act, 1869 
  11. Adulterer to be co-respondent 
  Upon any such petition presented by a husband, the petitioner
  
  shall make the alleged adulterer a co-respondent to the said petition, unless
  
  he is excused from so doing on one of the following grounds, to be allowed by
  
  the Court:
  (1) that the respondent is leading the life of a prostitute, and
  
  that the petitioner knows of no person with whom the adultery has been
  
  committed;
  (2) that the name of the alleged adulterer is unknown to the
  
  petitioner, although he has made due efforts to discover it;
  (3) that the alleged adulterer is dead.