This page of IGN's wiki guide concerns all the Assignments on the Citadel from when you first arrive on the station. In particular, it's designed to be done after you've finished the main Expose Saren ...

KCPD Criminal Record- After being greeted by Oscar you will have fallen down into a cave. Taking a few steps after the cut-scene you will see a split in the cave system, go right until the end where ...