The FBI investigation of former Secretary of State Hillary Clinton’s failure to protect state secrets contained in her emails has entered its penultimate phase, and it is a dangerous one for her and her aides.

Federal law enforcement sources have let it be known that federal prosecutors and the FBI have completed their examination of raw data in the case. After the FBI acquires raw data -- for example, the nature and number of the state secrets in the emails Clinton failed to protect or the regular, consistent, systematic nature of that failure -- prosecutors and agents proceed to draw rational inferences from that data.

Then they proceed to corroborate those inferences, looking for other sources to support or even to contradict them. With one exception, all of this work has been done with neutral sources of evidence -- documents, email metadata, government records and technical experts.

The exception is Bryan Pagliano, the one member of Clinton's inner circle who, with either a written promise of non-prosecution or an order of immunity from a federal judge, began to cooperate with federal prosecutors last fall.

Here is what he told the feds.

Pagliano has explained to federal prosecutors the who, what, when, how and why he migrated an open State Department email stream and a secret State Department email stream from government computers to Clinton's secret server in her home in Chappaqua, New York. He has told them that Clinton paid him $5,000 to commit that likely criminal activity.

He has also told some of the 147 FBI agents assigned to this case that Clinton herself was repeatedly told by her own State Department information technology experts and their colleagues at the National Security Agency that her persistent use of her off-the-shelf BlackBerry was neither an effective nor an acceptable means of receiving, transmitting or safeguarding state secrets. Little did they know how reckless she was with government secrets, as none was apparently then aware of her use of her non-secure secret server in Chappaqua for all of her email uses.

We know that the acquisition and corroboration phase of the investigation has been completed because the prosecutors have begun to ask Clinton's top aides during her time as secretary of state to come in for interviews. This is a delicate and dangerous phase for the aides, all of whom have engaged counsel to represent them.

Here are the dangers.

The Department of Justice will not reveal to the aides or their lawyers what it knows about the case or what evidence of criminal wrongdoing, if any, it has acquired on each of them. Hence, if they submit to an FBI interview, they will go in "blind." By going in blind, the aides run the risk of getting caught in a "perjury trap." Though not under oath, they could be trapped into lying by astute prosecutors and aggressive FBI agents, as it is a crime -- the equivalent of perjury -- to lie to them or materially mislead them.

For this reason, most white-collar criminal defense lawyers will not permit their clients to be interviewed by any prosecutors or FBI agents. Martha Stewart's lawyers failed to give her that advice, and she went to prison for one lie told in one conversation with one FBI agent.

After interviewing any Clinton aides who choose to be interviewed, the DOJ personnel on the case will move their investigation into its final phase, in which they will ask Clinton herself whether she wishes to speak with them. The prosecutors will basically tell her lawyers that they have evidence of the criminal behavior of their client and that before they present it to a grand jury, they want to afford Clinton an opportunity blindly to challenge it.

This will be a moment she must devoutly wish would pass from her, as she will face a damned-if-you-do, damned-if-you-don't dilemma.

Here is her dilemma.

If she were to talk to federal prosecutors and FBI agents, they would catch her in many inconsistencies, as she has spoken with great deception in public about this case. She has, for example, stated many times that she used the private server so she could have one mobile device for all of her emails. The FBI knows she had four mobile devices. She has also falsely claimed publicly and under oath that she neither sent nor received anything “marked classified.” The FBI knows that nothing is marked classified, and its agents also know that her unprotected secret server transmitted some of the nation’s gravest secrets.

The prosecutors and agents cannot be happy about her public lies and her repeated demeaning attitude about their investigation, and they would have an understandable animus toward her if she were to meet with them.

If she were to decline to be interviewed -- a prudent legal but treacherous political decision -- the feds would leak her rejection of their invitation, and political turmoil would break loose because one of her most imprudent and often repeated public statements in this case has been that she can't wait to talk to the FBI. That’s a lie, and the FBI knows it.

Some Democrats who now understand the gravity of the case against Clinton have taken to arguing lately that the feds should establish a different and higher bar -- a novel and unknown requirement for a greater quantum of evidence and proof of a heavier degree of harm -- before Clinton can be prosecuted. They have suggested this merely because she is the likely Democratic presidential nominee.

The public will never stand for that. America has a bedrock commitment to the rule of law. The rule of law means that no one is beneath the law’s protections or above its requirements. The DOJ is not in the business of rewriting the law, but the Democrats should get in the business of rethinking Clinton’s status as their presumptive presidential nominee, lest a summer catastrophe come their way.

Andrew P. Napolitano, a former judge of the Superior Court of New Jersey, is the senior judicial analyst at Fox News Channel.