Explanation:

1.  The writ of Certiorari is basically issued against the statutory bodies exercising judicial or quasi judicial powers. Such writ is issued against the authorities namely the government and the courts or other statutory bodies who have power to determine and decide the suit between the parties. Certiorari may apply when the administrative or executive authority fails to observe their duty to act fairly with respect to the administrative functions. The writ of Certiorari may also be issued against a subordinate tribunal even if the decision impugned is pronounced. 

2.  The writ of mandamus is ordered when the statutory authorities who entrusted with the duties fail to discharge its obligatory duty. It may be applied when the government authorities vested with absolute powers fail to perform their administrative and statutory duties