always lie to cops or don’t talk at all.
I’d rather deal with a judge with a lawyer
I've had to submit plenty of written statements to financial authorities but have thankfully only been formally interrogated in person once, and it was for an unrelated matter somewhere 7 years or so ago.
I used to be a cheapskate who bought weed off SilkRoad, because it was cheaper and I could pay with cryptocurrency. I'd usually order around 50g per package from the same seller, but one day his stock was empty and I bought from someone else. Long story short, the package ended up at an unspecified neighbor's home. They opened the package, saw it was a bunch of weed and called the cops.
So 2 armed cops showed up at my house, and at that time I was high. The ranking officer said "any idea why we're here?" and somehow I assumed it was for financial reasons, because my Paypal was frozen at that time due to a few dozen transactions that were apparently flagged as suspicious and potential money laundering. The freezing of my Paypal for that same reason happens practically every year but I get cleared and my Paypal unfrozen every time, it is what it is at this point.
So my dumb *** responded to the ranking officer with something along the lines of 'no but probably not for a friendly chat', so then she showed the package with my name on it that she had initially been holding behind her back and out of my sight.
Again, I was high during this moment, so I refused a warrantless search for obvious reasons but agreed to a voluntary interrogation without a lawyer.
I did answer every question that related to strictly my own conduct but initially started out with a lie until I eventually lost track of where I was going with the story and had to admit to lying a bunch of times throughout the various changes in my story. At some point I also tried to explain SilkRoad to the ranking officer by comparing it to buying a pair of pants on eBay, which further pissed her off.
Eventually the ranking officer wrapped it up and said that due to the quantity and transport across a border, I'd possibly also face a trafficking charge aside from regular possession.
I don't really know what ended up happening with the criminal investigation. I have zero doubt that nothing happened because I'm white. Sure I argued it was for pain relief/sleep (which was true) and had the medical records to back that up but it's still a slam dunk possession charge for any prosecutor. The trafficking charge should've been an easy slam dunk either.
At some point during the interrogation I even grabbed my laptop to fact-check certain details regarding quantity and order timing, yet my electronic devices were never even subpoenaed. The fact that such a basic investigatory step was never conducted leads me to believe charges were never referred to prosecutors in the first place, or the prosecutor immediately dismissed the case. In the end, I don't know what happened because police/prosecutors do not comment on whether your investigation is still open or dismissed.
Looking back on it with a more mature mindset, it really gives you a new perspective on just how privileged white people are when you personally experience something like this. I was expecting to be charged with at least possession, as virtually any non-white person would if they were in that situation. Meanwhile just for being white, I didn't even get a fine. Didn't even get arrested.
tl;dr: Never say a word to cops, or if you're in Belgium also don't ever talk to the cops or just flagrantly lie and minimize your culpability to the max if you're not facing charges with an intent requirement and are absolutely 10000% certain there's no one or nothing to expose those lies.