If you follow the news about federal investigations at all, you’ve probably heard the term “perjury trap” thrown around a few times. If you ever get involved in a federal investigation yourself, whether as the subject of investigators’ queries or merely a witness, it’s smart to understand what this term means.

Essentially, the “perjury trap” is what happens when federal investigators can’t prove that someone committed the specific crime that sparked the investigation — but that person ends up in jail anyhow for obstructing justice and perjury. Think of people like Roger Stone and Michael Flynn. Both men have complained of perjury traps set by aggressive federal agents during questioning.

How do people get caught in a perjury trap? It’s simple: Any lie you tell to federal investigators can come back to haunt you. While you have the absolute right not to talk to the police (even federal officers), you have no right to lie to them. Even saying something that you think is innocuous can be used as evidence that you were lying and trying to obstruct justice. For example, imagine that you say, “I don’t know anything about that” when investigators ask about your boss’s second bank account. You’re startled and scared — so you just want to buy yourself some time to think. Well, if investigators can prove that you did know about the second bank account, you could be guilty of obstruction.

The perjury trap is one reason that it’s smart never to talk to investigators on your own. Similarly, it’s wisest to have an attorney who is experienced with the nuances of federal criminal investigations by your side the moment that you’re aware an investigation is headed your way.