Crankydevin theft aftermath

Before Crankydevin was
banned for theft I was sold 12 blocks of diamond from him at 270$ a piece. Since there is a high probability that they were stolen I was wondering what should be done with the diamonds? I'm not asking for a refund since I got the diamonds at a great price at 30$ an diamond (cheaper than any shop that I know of). I am only wondering the policy ,written or unwritten, about this situation.

Sorry I don't have any screenshots that prove this claim but I was present when he sold the diamonds so I'm positive he was the one to sell me the diamonds.