Introduction to System of Islam by Jalal Ansari

This is a further type of judge who is appointed by the Khaleefah, but who is not concerned with the issues of the disputes that form the basis of jurisdiction of the other types of judges. Rather this judge and his department are responsible for appointing all the judges on behalf of the Khaleefah, and ensuring their conduct and qualifications are correct and in accordance with the Shari‘ah.

In this way, the Qadi al-Qada‘a would verify that any judge fulfils the conditions necessary for his authority to be valid. He would also look into any areas of injustice or misapplication of the Shari‘ah that any of the judges may have been involved in, and he has the authority to correct and expel any judges involved in corruption.