Former national security adviser Lt. Gen. Michael Flynn, through his lawyers, today invoked the Fifth Amendment right against self-incrimination and refused to hand over documents subpoenaed by a Senate committee.

The Senate Intelligence Committee subpoenaed Flynn's personal documents on May 10, after he declined to cooperate with its April 28 request in relation to the panel's investigation into Russian interference in the 2016 election and possible ties to Trump campaign associates. Before the April request, Flynn said through a statement from his lawyer that he wouldn't submit himself to questioning from the committee "without assurances against unfair prosecution."

The Fifth Amendment gives criminal defendants the right to refuse to testify at trial. No person shall be compelled in any criminal case to be a witness against himself, according to the U.S. Constitution.

Although a congressional investigation is not a criminal matter, Flynn would still have the right to invoke the Fifth Amendment with regard to certain questions that could potentially incriminate him in a future criminal case. But he does not have the right to refuse to testify before Congress altogether.

As a general matter, the Fifth Amendment applies only to testimony and does not give criminal defendants or witnesses in congressional investigations the right to refuse to turn over subpoenaed documents. But there is an exception when the act of producing a document is itself incriminating.

The fact that the content of the documents are incriminating does not give you a Fifth Amendment right not to produce them, explained Michael Seidman, a criminal law professor at the Georgetown University Law Center. But the mere act of producing them can be incriminating if the government doesnt know that they exist or that you have them.

If the government already knows that certain documents exist, it could turn into a complicated legal question about whether Flynn must release them, said Seidman.

In a letter to Sens. Richard Burr, R-North Carolina, and Mark Warner, D-Virginia, and the Senates Select Committee on Intelligence dated May 22 obtained by ABC News, Flynns lawyers argued that [p]roducing documents that fall within the subpoenas broad scope would be a testimonial act, insofar as it would confirm or deny the existence of such documents.

The context in which the Committee has called for General Flynns testimonial production of documents makes clear that he has more than a reasonable apprehension that any testimony he provides could be used against him, the letter reads.

Seidman said this is a standard legal strategy and that any competent lawyer would tell Flynn that if he might have a Fifth Amendment privilege he should assert it. Also, if he produces documents and makes statements, he risks inadvertently waiving his rights against self-incrimination as the Russia investigation progresses, Seidman said.

Legal experts also pointed out that if Flynn is granted immunity from criminal prosecution, then he would no longer have Fifth Amendment rights against self-incrimination and could be compelled to answer all questions and release all documents.

In the same way that immunizing a low- or mid-level person in a crime ring can lead to fingers pointed all the way up to the Don, said Akhil Amar, a constitutional law professor at Yale Law School, who said the Don pun was intentional.

Members of the Senate Intelligence Committee said today that they would use all available tools to get information from Flynn, including holding him in contempt of Congress, which could open him up to criminal charges.

We're going to keep all the options on the table, Warner told ABC News.

We're going to help honor the constitutional rights but we still have to be able to get to the facts. We can't just step back and say, Oh, OK we can't get it, added Sen. James Lankford, R-Oklahoma, another member of the Senate Intelligence Committee.

Lankford also suggested that the committee will still try to negotiate with Flynns lawyers to get access to the information he is currently refusing to share.

Warner added that there might be a legal gray area that prohibits Flynn from using the Fifth Amendment to protect his refusal to provide documents, versus his clear constitutional right against testimony that might incriminate him.

We know there's a Fifth Amendment right on testimony but I think there's an open question on documents and we're looking into that right now, he said.

ABC News' Ali Rogin and Mary Bruce contributed to this report.

Follow this link:

What you need to know about the 5th Amendment and how it ...