How to defend myself in court?

First, I would go talk to the other guy who had his food stolen. I have to say this is pretty low on his part. You didn't know anything about what happened. Offer to work out something with him and ask him why he didn't come to you first about it. Tell the truth. You didn't see anything and you didn't know what happened. After that, if they still are causing you problems I think I would be suing.