Simply make a notarized statement of which address belongs to whom, and that a transaction from x to y for z amount means that the funds are effectively transferred.
Then if I won the auction, after signing the deeds I would simply send the funds from my notarized bitcoin address to your notarized bitcoin address.
That's it, that should suffice.
But if you want to make it even more undeniable, just make each parts to sign a note with their bitcoin addresses, with a clear statement that such bitcoin address belongs to NAME, SURNAME at ADDRESS, NATIONALITY AND ID#. Both parties print them out, sign it, and notarize it just for the records.
ultimately, if trust is such an issue, all of this could be solved in the notaries office with a laptop.
Buyer- click- bitcoins transfered
Seller- sign- property transfered
House sold......
The receiving part could say that the receiving bitcoin address is not his, or to prevent accusations of having mistyped of the address or claiming that the receiving funds are from a cousin and not from the buyer (the last one would be quite dumb, but could complicate things)
If there is a signed and notarized statement that x bitcoin address belongs to the buyer and y address belongs to the seller, there are no excuses possible.
I think it is necessary as a prophylactic measure.
Yeah, I think this would prevent the seller from being scammed himself.
It's always better to be safe than sorry.