You can, but this is the kind of thing which is very easy to get wrong in ways which are significant legal risks on their own.
For example, if you were some random cryptobro buying personal quantities of drugs in 2015 there’s some risk but the FBI probably isn’t going to spend time on something that small. If you do anything which reveals funds going to or from a tumbler, however, the risk isn’t just KYC but also questions like who else used that tumbler - if you were participating at the same time the North Koreans or a big ransomware ring were laundering something, that traffic might be a lot more likely to get analyzed and in the worst case scenario some agents show up trying to get you to convince them that you were unwitting small fry and not hiding more. Lying to them is a federal crime, too, so even if you nothing other than tumble coins for ideological reasons you’d want to be very careful about what you say – and think about how hard it could be to prove you didn’t know the other parties in a transaction.
>Lying to them is a federal crime, too, so even if you nothing other than tumble coins for ideological reasons you’d want to be very careful about what you say – and think about how hard it could be to prove you didn’t know the other parties in a transaction.
This is true. However, I'd present a few caveats:
1. Even though it's a felony to lie to Federal (and some state/local) law enforcement in the US, you can just not speak to them. In fact, you should mostly not talk to the police under any circumstances. There are many reasons for this. Too many for me to list here. However, this attorney and a former police officer[0] (48 minute video, but well worth it. Share it with your friends and family too!) provide all those reasons.
2. Law enforcement aren't superhuman. They're just as dumb (or smart, but the really smart ones end up in corner offices rather than police stations like police and more common criminals) as the next guy. Their big advantage, especially in a circumstance like this, is that they only have to get it right (i.e., find some evidence) once. The alleged perpetrator of a crime needs to get it right (in covering their tracks, destroying evidence, etc.) every single time to make sure they aren't identified and caught.
So, unless you're prepared to cover your tracks (in this case, it was bitcoin transactions) over and over forever, you run the risk of being caught -- eventually.
I'll say it again, because it's an important point: If you're in the US (not just a citizen, anyone present within its borders), DON'T TALK TO THE POLICE!
I'm sure things are different elsewhere (perhaps someone could expound on that?), but in the US, just STFU.
> So, unless you're prepared to cover your tracks (in this case, it was bitcoin transactions) over and over forever, you run the risk of being caught -- eventually.
This is really the main thing I was thinking about: it’s been bizarre how the salespeople kept going on about bitcoin being anonymous when it’s more like “if you do everything perfectly, you probably won’t be tracked. As far as we know now.”, which is just incredibly fragile.
You're referring to the risk of getting chased down for the "bad deeds" of others after funds are co-mingled. You're not explaining that it's prohibitively risky or not possible.
Further, I'm only aware of tumbling blacklisting [0], where the exchange gets blacklisted for co-mingling known dirty funds. AFAIK, there are still sizable tumbling vectors.
My point was simply that your options with Bitcoin for converting it into real currency or goods are either easily tracked (mainstream exchange following KYC laws) or push you into riskier activities. As with most things, the odds of getting caught aren’t certain but one somewhat unique risk to most cryptocurrencies is that you have to estimate the risk of retroactive punishment since the ledger is irrevocably public.
That’s already stressful and expensive but consider also that you’re probably only having that conversation if they already have evidence for at least one crime (disclosure and/or taxes). That is likely going to be grounds for a search warrant to examine everything else, and even if that’s ultimately fruitless it’d be an ordeal and could lead to professional consequences as well as things like losing your devices to a forensic lab.
[0] https://en.wikipedia.org/wiki/Cryptocurrency_tumbler#