If you read the indictment, they claimed they had bitcoin from mining in 2011, the exchange asked for further proof, and they just abandoned the bitcoin (~$150k). The exchange surely notified the authorities, because who abandons $150k of legit bitcoin?

So claiming it was from mining didn't work in this particular instance.

They don't need to prove you are lying in all instances, it's enough to prove you are lying in one instance. They will get you for that one instance where you didn't launder it properly if they are after you.

I'm surprised the exchange notified the authorities. Are they forced by law?

That sounds impossible, wouldn't people be able to see that the account didn't have those coins in 2010?

I think the point is that it technically isn't illegal to mine coins, later mix them, and then sell them. It is very suspicious though.

It's very common to use more than one account, and send money between them for various reasons.

you would need to show crypto addresses from 2010 and prove that you still have access to them