law: Indian Evidence Act, 1872 
  29. Confession otherwise relevant not to become irrelevant
  
  because of promise of secrecy, etc.
  If such a confession
  
  is otherwise relevant, it does not become irrelevant merely because it was made
  
  under a promise of secrecy, or in consequence of a deception practiced on the
  
  accused person for the purpose of obtaining, it, or when he was drunk, or
  
  because it was made in answer to questions which he need not have answered,
  
  whatever may have been the form of those questions, or because he was not
  
  warned that he was not bound to make such confession, and that evidence of it
  
  might be given against him.