Just read the article (Finally) as I said before, there are always smart criminals who figure to get away with it, have met many of them and made hotel arrangements for many many more in my time as a police dispatcher. (The Gray Bar hotel that is).
In this case.. I think I'd be inclined to demonstrate to the suspect one manner in which his knife might be used.. (I will not describe that manner here, leave it to your imagination) But in truth.. Once he is convicted and sent to prison..... They will take care of that demonstration, no need for me to lift a finger.