law: 175. Power to summon persons.-
  (1) A police officer proceeding under section 174 may, by order in writing, summon two or more persons as aforesaid for the purpose of the said investigation, and any other person who appears to be acquainted with the facts of the case and every person so summoned shall be bound to attend and to answer truly all questions other than questions the answers to which would have a tendency to expose him to a criminal charge or to a penalty or forfeiture.
  (2) If the facts do not disclose a cognizable offence to which section 170 applies, such persons shall not be required by the police officer to attend a Magistrate's Court.