If only it worked that way. You receive no legal protection whatsoever by turning your dollars into BTC. He will still owe the money, it does not matter that he bought a house with it or bitcoin. His estate will be seized, bitcoin and all. If he thinks he can just refuse to give up his private key then he will spend his life in a cell on contempt charges. Not smart.
Maybe you underestimate Mr. Cosby.
He could show some remorse and give up the private keys to the corresponding
wallets that contain the BTC equivalent of 5M $.
This amount matches the BTC amount reported by the media and all
creditors and the court are happy.
Afterwards Mr. Cosby secretly sells off his remaining BTC whenever he needs some fiat,
because he obviously bought way more than 5M$ of BTC and just spread this
rumor in order to downplay the true extent of his BTC holdings.
Personally, I don´t really like this news, because Mr. Cosby will be filthy rich
when BTC hits higher price levels. I can think of persons that would be more deserving
of that kind of unprecedented wealth than him.