Are fingerprints purged form the system in Cook county if no charges are filed?

In Marchm my landlord had the police take me in and run fingerprints, and they held me for several hours, although I was never formally charged with any crime.

(I was in the process of suing my landlord at the time - I think this was retaliatory)

Are my fingerprints still "on file" ? Somebody told me I can request that they be purged...? Is tis true?