Back in 1980, Donald Trump strode alone down the hallway of the federal Organized Crime Strike Force office in Brooklyn.

He was there to be interviewed by the famously tough U.S. Attorney Michael Guadagno concerning possible dealings with labor racketeer John Cody.

The sight of anyone of means coming in for questioning without legal representation was rare enough to prompt an exclamation from another strike force prosecutor.

“What the f---?”

“He was in without a f---ing lawyer!” Guadagno is said to have replied.

Trump may have chosen to come solo on the advice of Roy Cohn, who was by then his lawyer and mentor. Or Trump may have been acting with a sense of his own infallibility. He seems to have been responsive to Guadagno’s questions and generally less impetuous and more considered than many of us might have imagined.

“I believe the guy, what can I tell you?” Guadagno is said to have remarked afterward.

Guadagno had almost certainly been aggressive in his questioning and Trump may have actually been telling the truth in insisting he had no corrupt dealings with Cody to obtain labor peace.

But that may have subsequently changed. Doubters would note that the Trump Tower construction site was the lone site that remained open during a citywide strike Cody called in 1982. And that a lady friend of Cody’s subsequently ended up with a Trump Tower penthouse, the only apartment there with its own swimming pool.

Guadagno would go on to become a state appellate court judge in New Jersey. He married a fellow strike force prosecutor, Kim McFadden Guadagno, who became New Jersey lieutenant governor.

And Trump became president of the United States.

Now, 38 years after that solitary stroll into the Brooklyn Strike Force office, Trump again faces questioning by the feds. This time it will be by special counsel Robert Mueller and his investigators.

Trump presently has a host of lawyers, but he very likely still harbors an impulse to go solo as he did in 1980.

If he did so, the whole country would exclaim, “What the f---?”

His base would be electrified, especially if he went so far as to tape it.

Talk about reality TV!

One complication is a change in the law. Trump can still lie all he wants about special counsel Robert Mueller and the FBI. But if he lies to Mueller or the FBI, he risks being charged with a crime thanks to a precedent arising from a 1998 Supreme Court case involving another New York real estate company and another New York labor union official.

Prior to then, people who lied to the FBI could seek the protection of the Exculpatory No Doctrine, which held that the Fifth Amendment provision against self-incrimination precluded a person from being charged with a crime for falsely denying guilt when questioned by a federal investigator.

The union official in this landmark case was James Brogan. Federal investigators appeared unannounced at his home and asked if he had received any illegal cash from a particular real estate firm, JRD.

“Petitioner’s response was ‘no,’” court papers report. “At that point, the agents disclosed that a search of JRD headquarters had produced company records showing the contrary. They also told petitioner that lying to federal agents in the course of an investigation was a crime.”

Brogan was convicted and his appeal of Brogan v. United States went all the way to the Supreme Court. The court’s decision summarized Brogan’s argument that in making it a crime to lie to the feds, the statute “places a ‘cornered suspect’ in the ‘cruel trilemma’ of admitting guilt, remaining silent, or falsely denying guilt.”

A majority of the justices did not buy it.

“An innocent person will not find himself in a similar quandary,” the court found, indicating that “the innocent person lacks even a ‘lemma.’”

The court added, “Even the honest and contrite guilty person will not regard the third prong of the ‘trilemma’ (the blatant lie) as an available option.”

While warning against what it termed “compassion inflation” in the law, the court ruled, “Whether or not the predicament of the wrongdoer run to ground tugs at the heart strings, neither the text nor the spirit of the Fifth Amendment confers a privilege to lie.”

As a result of that new case law, Martha Stewart later went to prison.

Brogan v. United States also led to the recent cases against Trump’s former national security advisor Michael Flynn and former campaign foreign policy advisor George Papadopoulos.

“ Violation: 18 U.S.C. § 1001 (False Statements),” their indictments both read.

In the absence of being able to cite the Exculpatory No Doctrine, both defendants pleaded guilty to making “materially false statements and omissions during an interview with the Federal Bureau of Investigation.”

Flynn and Papadopoulos are both reportedly cooperating. The feds may now have more on Trump than they did in that long-ago encounter. And, in an investigation of this size and importance and where he is the ultimate target, the feds would not likely be seeking to talk with him unless they were nearing the end of at least a major portion of it. They will therefore likely already know the answers to whatever they ask. Any false replies could bring into play the change in the law since he strode solo into the Strike Force nearly four decades ago.

Yet, when speaking to reporters on Tuesday, Trump displayed some of the same bravado. He declared that he was looking forward to facing Mueller.

“I would love to do that,” he said. “I’d like to do it as soon as possible.”

He allowed that this time, the questioning will be “subject to my lawyers and all that.” He said they estimate it will come in “about two to three weeks.”

When the big moment arrives, his bravado will likely give way to surprising sobriety for a Trumpaholic who is so often inebriated with his sense of Trump. He may well be even more measured than he was back in 1980. He may even set a personal record for truthfulness with Mueller, outdoing his session with Guadagno.

Meanwhile, in circumstances that do not involve the feds and liability to 18 U.S.C. § 1001 , Trump is free to continue breaking all presidential records for lying. He is sure to give vent to his impetuous self as he tweets smears and innuendo and falsehoods.

From the Oval Office, he speaks power to truth.