Every citizen has right to see that his complaint is properly investigated.
If he has reasons to suspect that police has joined hands with other side and is not properly investigating complaint, then an application under Cr. P.C. sec 173(8) can be made to trial court. Trial Court will then direct investigation by Higher Police officials.
For exact or more detail look at website of Supreme Court for judgement dated 12.01.12 Azija Vs State of Maharashtra also reported in 2012(1)SCALE page 328
in Criminal appeal No. 126 of 2012