Chipmixer was never supposed to store private keys after session deletion and guess what? People had coins seized that they transacted 3 months ago, like me.
I already wrote about this situation in chipmixer thread.
Never trust centralized mixers on what they state.
Even my chips which I had in chipmixer service for which they claimed to "delete private" keys after 7 days or whatever, were seized/transfered.
and these transactions took place good 3 months ago.
You can assume that they stored history on everything including input and outputs and this data is now in LE hands. Although in most countries using services like this is perfectly legal and they cannot accuse you of anything. Receiving coins that someone else obfuscated via CM and sent to you is also not illegal. You have to be proven that you did obfuscate these coins yourself, which is a hard case, assuming you used VPNs/TOR while using CM website. Regarding the data, even if they have now all historical transaction data, it is nothing new. All chipmixer addresses and transactions were easily visible in the blockchain even without the seizure of data - due to the unique chip size and very schematic process.
The operator of the website has a bigger problem cause they're gonna put him into jail for ages for creating this. Chipmixer grew too big and was part of ransomware schemas including high-profile hacks of North Korea. They accepted it and did not try to prevent it. Additionally, they refused to respond to LE contact when they seeked information in these cases by contacting chipmixer.
DOJ/FBI claims the operator of the website was identified due to OPSEC mistake where he sent funds to one of Paypal accounts associated with CM from his real identified Paypal account. Check page 32 of indictment. They digged very deep and even successfully probed ProtonMail for information, not a real surprise considering how big and popular the chipmixer service was.
They were also able to identify server serving TOR website hosted in Hetzner, it is not disclosed how they managed to find out the real IP address of .onion website. After finding the server they probed the PayPal account which funded the hosting service, checked the logs and found out chipmixer operator identity and now they can prove it was directly linked to funding chipmixer infrastructure/operations.
The amount of the charges he got is not really big for the scale of the service.