Copy this question and post it under the practice area "Employment law" and under "Civil Rights." You'll get a wider response. Your criminal case has already been resolved so you don't really need a criminal defense lawyer.
I agree with wht you say your PD said,. However, I believe that since you entered a plea, you may not sue.
This is a government entity and employee. You have limited time to file a complaint upon which you may later file a suit. See a pi attorney who regularly sues copps/the government. Should be able to get a free consultation.
The above is not intended as legal advice. The response does not constitute the creation of an attorney client relationship as this forum does not provide for a confidential communication.
The fact that you plead guilty to the disturbing the peace charge may prohibit you from claiming your rights were violated, or at least create difficulty for any future civil rights case.
You should contact a local civil rights attorney for a consultation - someone who can review the records from your criminal case.