I am going to go with no.

Technically, you should declare them, as you are bringing something in which will be left behind. Scuffing them up, etc as melody said is still skirting the law... That said, I highly doubt that even did you decide to declare them on your customs form that anyone is going to say a word. It's not like you are bringing a shipping container of shoes into the country for profit. It would cost more in effort for the customs officer to get your paperwork done for the duty of three pair of shoes then the duty itself would justify.