If you got caught here and you were under 18.
You can get 3 cautions, but if you say you didn't do the graff that they are accusing you of, they will take you to court.
Then after the 3 cautions if you got done again for anything, You get a "conference", Which is when the cops and the owners of the property you painted (I don't know what happens if it's public property, Maybe a council representive.) Are in a room together with you and try to figure out what will happen to you, Usually a fine or community service.
Then again if you got done for anything after that it's court.