Bought bitcoins? Sold them? In exchange for what? Drugs? Guns or bombs? Pirated movies? This isn't looking very good for Bob the Bitcoin Launderer.
The police found out that wallet X is Bob's (because he exchanged bitcoins for something useful), and that Bob was illegally hiding ownership of that wallet. Bob is probably going to end up with the burden of proving that each transaction from wallet X was with a third party, rather than Bob trying to launder bitcoins to other wallets he controls -- after all, the government knows Bob was trying to hide his bitcoins. Otherwise the law might say he must forfeit a monetary equivalent to those bitcoins, even if he claims to not own them any longer. On top of that, Bob will need to pay a transaction fee whenever he shuffles bitcoins between wallets.