Also there is a good question is there some limit or ratio of tainted coins that would be considered non incriminating. Or if there isn't would single satoshi taint all coins? If there were wouldn't dilution of funds be possible? That is wash them by sending to wallets with enough funds...
That's assuming a BTC miner even agrees to process the transaction. Why would a BTC miner want to deal with the headache of tainted bitcoins? It's such a problem that Marathon Digital Holdings, a major bitcoin miner, has stated they will refuse to process transactions from tainted addresses. In the near future, I expect more mining pools to do the same.
Would you return stolen goods to the thief? How about return it to the owner/authorities. May not be simple but certainly better than sending it back. If all else fail there are black hole addresses to forever lock the BTCs.