Michael Flynn is pleading the fifth to decline a subpoena - here's what that means

On May 22, former National Security Adviser Michael Flynn had chosen to plead the Fifth Amendment in response to a subpoena from the Senate Intelligence Committee (SIC). The subpoena called Flynn to supply any and all documents related to his involvement with Russian officials within the last two years.

The case raises a number of political questions, many of which are not yet answerable. But there is one logistical question that can be explained: What does it really mean to plead the Fifth?

Invoking your Fifth Amendment right, as outlined by the US Constitution, can pertain to a number of different circumstances, including getting prosecuted for the same crime twice ("double jeopardy") and self-incrimination.

Flynn is pleading the Fifth for the latter. The SIC is asking him to participate in what could become, should the documents contain incriminating information, Flynn's own legal demise. He has a constitutional right to avoid such a scenario before any possible trial.

This holds true for ordinary civil and criminal cases, which are tried by juries, and special investigations, like this one carried out by the SIC. "You can't be compelled in any context in which the evidence, if produced, could eventually be used against you in a criminal case," Georgetown University law professor Julie O'Sullivan told USA Today.

However, the SIC could try to claim the documents must be handed over under the "forgone conclusion doctrine," O'Sullivan says. Basically, the Supreme Court has the power to request documents it knows to exist - in this case, conversation logs between Flynn and the Russian ambassadors, among any others.

There's a great deal of precedence for pleading the Fifth. One of the more landmark cases came in 1968, with Haynes v. United States, in which the Supreme Court ruled it unconstitutional to require felons to register their firearms. Since it's illegal for felons to own firearms in the first place, requiring them to register them would be a form of self-incrimination.

Flynn, Trump's pick for national security adviser, resigned from his position as national security adviser on February 13 after news broke that he had lied to Vice President Mike Pence about his broader dealings with Russian ambassadors to the US.

One of the paradoxes with pleading the Fifth is that doing so tends to raise suspicions of guilt anyway, since it's assumed innocent people should have nothing to hide. President Trump has said as much in the past.

"The mob takes the Fifth Amendment," Trump said at a rally in Iowa. "If you're innocent, why are you taking the Fifth Amendment?"

The next step for the Senate is deciding whether to hold Flynn in contempt for refusing to hand over the documents. If it does, the matter would head to a civil court in which a judge would decide whether Flynn's Fifth Amendment right applies in this case. Republicans have an obvious incentive to fight this transition; however, the same paradox will quickly apply.

The further Flynn's case gets dragged out, the worse it begins to look - unless, of course, it turns out the documents contain nothing of value.