As Robert Mueller's investigation continues into possible collusion between the Trump administration and Russians seeking to influence the 2016 election, I've got some free legal advice for the president of the United States: Don't talk to this guy voluntarily and, if subpoenaed, take the Fifth like a dime-store mafioso without batting an eye.

I write as a non-lawyer and as a non-fan, non-hater of Donald Trump. I write as someone who is seriously worried about the ways in which law enforcement routinely screws people not by catching them red-handed in a crime but by nailing them on things that are criminal-adjacent rather than the crime itself. I write as someone deeply concerned about factions within the government using largely uncontrollable powers to dispatch enemies.

If there's one thing even more foolish than a lawyer who takes himself as a client, it's anyone who freely talks to law enforcement when they can avoid it (which Trump can). As defense attorney, former federal prosecutor, and influential legal blogger Ken White wrote recently at Reason:

When the feds interview a subject or target, their goal is not mere information-gathering or fact-finding or "clearing a few things up." Their goal is the hunt....

The purpose of the "hunt" is to catch witnesses in a lie that may or may not really matter much to the larger issue at hand but will count enough to underwrite a conviction for, well, lying to law enforcement. That's what Trump associate George Papadopoulos got nailed for, and Michael Flynn too. Back in the day, that's what cost Martha Stewart her freedom (contrary to popular wisdom, her jail time had nothing to do with insider trading and more to do with defending herself in public). Once you've got someone on lying, obstructing justice, or anything else, you can then flip them to move up the pyramid to catch Mr. Big. Who in this case is Donald Trump.

When special counsels or FBI agents ask questions of one of these powerful people, they are not fact-finding. They've already done their homework. They've already gathered facts—almost certainly many more facts than the interviewee knows. They are asking questions the answers to which they can already prove, hoping that the interviewee will tell a provable lie, and thus commit a crime, or at least lock themselves into a feckless story that ties their hands later. The law that makes it a crime to lie to federal investigators does not require the lie to fool the investigators for a nanosecond. A lie must be "material" to be criminal, but that only means that the lie is the kind of statement that could conceivably influence the government, not one that actually did. The FBI can roll up with irrefutable proof of something, ask the target a question hoping for a lie, collect the lie they wanted, and reap a felony conviction.

Recall too that in the end it was Bill Clinton's lying and attempts to circumvent legal prosecution that got him into his most serious legal (though not political) trouble. There's no way to play nice with federal investigators and Trump has more leverage than any other person in America to push back and not participate, at least not voluntarily.