In the real world the one who claims something has to put the proof of his claim on the table!
Okay, cool. Where's the proof that you had not scammed over the past 3.5 years?
No proof available that I scammed someone is the proof!

I challenge you to place this 5 BTC with a trusted escrow and clear terms. Otherwise all this is, is free PR for you with zero risk. You won't however, because you are afraid some one might claim it and you would have to pay to expose your own criminal activity

The fact that you refuse to do this is proof you never intend to honor your word.