After yesterday’s travesty of an Intelligence Committee hearing with its no-answer answers, there are some ground rules worth understanding. A witness in a Senate hearing is ordinarily expected to answer questions with “the truth, the whole truth, and nothing but the truth,” as the standard Senate oath provides. The exceptions are very few, and absent a proper exception, the witness must answer the questions.

One exception is that a witness may refuse to answer as an exercise of his right against self-incrimination under the Fifth Amendment — “pleading the Fifth.” No witness claimed this privilege yesterday, so we can set that one aside.

There are common law, testimonial privileges that can be asserted in court that may be honored in congressional hearings: a husband or wife cannot be forced to testify against their spouse; an attorney cannot be forced to disclose certain matters about their client, and so forth. None of these testimonial privileges was relevant to, or asserted in, yesterday’s hearing. Set them aside too.

Another claim is “executive privilege,” made famous in the Nixon era, protecting the private conversations of the President with his senior advisers. This privilege ordinarily must be asserted by the President, and neither the White House nor the President asserted that privilege with regard to this hearing. Under pointed questioning from Maine’s Senator King, the witnesses also did not claim “executive privilege.” So that privilege was not in force, either.

Finally, if a question is outside the scope of the hearing, the chairman can rule the question out of order and the witness does not have to answer. But this is not a protection that a witness can assert; it is the chairman’s prerogative to limit the questioning, not the witness’s, and Chairman Burr never exercised this prerogative. So this too can be set aside.

A legitimate reason not to answer is to protect classified information. But the information here actually has to be classified, and the witness has to be willing to answer the question in a closed, secure setting. If a witness says he’d be willing to answer in a closed, secure setting but not in public, he is asserting that the underlying information is classified or could lead an attentive enemy to discover classified information. If that’s not the case, it’s wrong to say this.

Investigative information in a criminal case is also protected, and it is proper for a witness to refuse to answer questions about an ongoing criminal investigation (“whom are you investigating and how’s it going?”), or about investigative information derived in a criminal case (“what have you discovered, and can we see it, too?”). This protection applies even in a closed, secure setting; because the purpose here is not to keep information from enemies who may be listening, but to protect the independence and integrity of the investigation from political abuse or interference. Members of Congress should not be privy to such information, and it’s actually worse if legislators inquire about criminal investigations out of public view — mischief is more likely in the dark.

For this protection to apply, the answer would actually have to disclose information about the investigation. A fact witness with information prosecutors also obtained can still properly answer a Senator’s question about that information. It would be improper to pry into the criminal investigation through that witness (“what did you tell the prosecutors?”), but their factual evidence (“did the mayor hide the money in your basement?”) is not forbidden to Congress just because of an investigator’s interest in the same fact.

Some form of “air traffic control” should be set up to address “deconfliction” between congressional and criminal investigations, so that each can proceed with minimal interference to the other. A congressional committee calling a witness who is cooperating in a criminal investigation, for instance, can cause all sorts of problems, particularly if his cooperation is not known. Despite congressional requests, the Department of Justice has not set up such a mechanism yet.

Investigations with both criminal and counter-intelligence components create even more complex boundary issues, because Congress can be briefed on counter-intelligence investigations. In the counter-intelligence space, you’re dealing with classified information, to which Congress can have access in a properly secure setting; Congress has no business in criminal investigations, classified or not.

The word salad of reasons not to answer questions from the witnesses in yesterday’s Senate Intel hearing was an embarrassment to the traditions of the Senate, and an impediment to legislative oversight. There is no such lawful thing as a witness refusing to answer a Senator’s questions on grounds of “inappropriateness,” without reference to one of these legitimate grounds. The American public deserves more candor, a clear and specific basis for refusals to answer questions, and better deconfliction.