Landlord stated in writing that I would get my full deposit back but did not do so.

I am a lawyer in CT and practice in this area of the law.  It seems that the landlord went against its promise.  however, the landlord does in fact have 31 days to return the deposit aftet you move out.  generally, the landlord does a walk thru of the apartment and determines whether there are damages that you are liable for.  if there are, the landlord is required under the law to send you a written itmization of the damages.  you may sue the landlord for not providing this itemization and possibly collect double the security deposit. I suggest that you hire a lawyer to review what was sent to you and all communications with the landlord to determine whether you have good grounds to sue the landlord for retaining the deposit.