For all you gents who are hoping that the little tool in question will feel sorry, contrite, humbled, apologetic, etc, I'll share this with you.
As a landlord in distressed communities, which is a polite way of saying that I own a couple buildings in shitty neighborhoods with shitty tenants, I can tell you that once someone has committed to scamming people, their ability to be remorseful about bad behavior is right out the window. It's gone.
I see this kid as akin to any other addict. His perception of reality is as follows - reality is as he wants it to be, not as a collective observation would assess it. When he says he did not use the knives, it's possible that in fact he truly believes, at that moment, he did not use the knives. He will admit quietly that he did, but when it comes time for a public admission he will scream up and down that this is not the case.
Our legal system is currently designed to coddle degenerates like this. Whether the behavior is compulsive lying, as in this case, or a crack habit, the addict is treated as a victim and therefore it is possible to rehabilitate him.
Having witnessed firsthand that lack of essential civility and decency on a grand scale, in one case the destruction of the inside of a house and the burning of a garage, I can tell you that someone engaged in behavior like this will not change voluntarily. The pain felt must outweigh the need to engage in poor behavior. Petty and not so petty theft is a natural to people who have a compulsive entitlement attitude.
I'm glad to see him "permabanned," whatever that means. The little toad engaged in such enterprise will not change, since currently Grandma is covering for him. That is a noble thing for her to do, and frankly, as the guardian it's the correct thing, since legally she's responsible for this mess. I doubt highly that she has actively sought to foster it, but her admission that the kid has a problem with lying tells me, and this is only from the point of view that I can get by reading this, is that she is used to dealing with bullshit like this, and she's terrified of letting him bear some real consequence on his own nutsack.
Grandma, I'm really sorry about this, if you are reading this, but goddamnit, you need to man up a little here. If the kid does not have some harsh reality injected here, odds are he will continue to behave like this.
Note that some of the lads here have local friends, and the implication that not all of their friends are as well-behaved as we collectively are. That MAY be a knee-jerk reaction, but imagine the pleasantry of a visit from someone fairly local, and now pissed off, about the theft of a knife worth several hundred dollars, proof in hand of such theft, and your grandson stalling for time on the front porch. Sound like fun?
What if the dispute was over drugs? I suggest that this is a genuine possibility and acting like this while drug money is involved, we've all seen how that works out.
Or perhaps it is instructive to think about how some people of high emotions may react when Garret tries to steal money from someone's house at a party, or starts writing bad checks, pulling shennanigans like this with stolen property and selling/ trading it with local bad guys. He is going to eventually get really fucking stomped but good.
He's not going to change with Grandma wistfully complaining that he has a problem with telling the truth and frankly, based on his behavior, I'd get that kid in for some drug testing today, and then also testing for any other chemical imbalances. I'd followed by a visit to social services for recommendations for a "reality check" boot camp. The state tends to pay for such things and not only will his excess energy be drained off, but he'll be exposed to an atmosphere where his retarded behavior will meet immediate consequences without fear of genuine physical harm.