The fence is what we decided on.
Well lets hope he doesn't go out at night, and simply cut it up. It's not illegal for him to be on the property at night, just to hunt at night (depending on the critter). It is illegal for him to cut your fence, but he has to get caught, and he thinks he can't be caught.
I would venture to guess he will damage the fence. IF he has the slightest amount of brains, he will modify the fence so he can get under it..., then he will shoot onto your property, kill deer, tresspass, drag the deer back to his fence modification, and slip the animal under it.
It also doesn't prevent him from merely slaughtering deer on your property to mess with your hunting, as he is in an elevated stand/blind, he can shoot over your fence without problems, just for spite.
I wish you luck, but having dealt with this sort of situation in the past, I predict he will continue to be a problem until he is actually caught and charged with something.
Since "Dad" won't deal with it, he must be a juvenile, so one way to get Dad's attention is to file suite to recover the cost of the fence necessitated by his son's actions and his failure to deal with the problem. Then get a "restraining order" while the suit is progressing, that requires the son to stay away from all property (including land) belonging to you, for a distance of 100 yards. This should prohibit the kid from even setting foot on the acre in question.
Now the kid won't obey, and when spotted in violation of the order, get a photo, call the cops, have him arrested for violation of the order. Keep putting off judgement of the suit, and keep renewing the restraining order. You might be able to string this out for a couple of years or more. If dad has to come-out-of-pocket for a lawyer, has to appear in court, give a deposition, etc, he may just tie a knot in junior's arse about the situation.
This isn't a cheap solution..., when you use the legal system it's never cheap, but if you can't find a LEO who wants to help in return for hunting some on your property, you probably will end up spending some money in the long run.
LD