I traveled to Italy to study abroad 2 years ago and recieved a bus fine in the middle of my trip. I belive it was ATAF, the local city bus. I was confused on how to pay and got on expecting to pay on there. Once I realized there was nowhere to pay we were already off. The next stop a ticket agent came on to check out tickets and took me off the bus. They handed me a fine and told me to pay by a certain date. Upset of course, I tore it up and threw it away. I left Italy not thinking much of it but now I want to go back and I am unsure what would happen if I did. Would they detain me? Would I go to Jail? Would they charge me 1,000 euros to enter and cover my fine? Just looking for answers, I am having a hard time finding much on this.
Normally when you get fined for fare evasion the fine is an administrative one. So they will send you a bill to your home address, and if you do not pay, a reminder.
If you do not do that they may, or may not, decide to take this to court. Some countries take this more seriously than others. (In Switzerland for example they will not just drop this). If you do not appear on your day in court then they will make in entry in the Schengen Information System, and you will be in trouble the next time you enter Europe (not just Italy).
Being detained at the border for an outstanding fine does actually happen. It is what the Schengen Information System is there for.
All the previous answers seem legitimate, except the question itself is rather curious to me: however I will still attempt to clarify your doubts.
No jail, no 1000 euros, no court, no SIS, no ECHR (which was made to protect those who owe tens of thousands, not for a 30 euro bus fine), no prison. If you really can't find peace, then give a call to ATAF instead of asking here.