Donald Trump speaking to supporters in Arizona in 2016. (Gage Skidmore / CC BY-SA 2.0)

Did the 45th president of the United States obstruct justice in his firing of former FBI director James Comey? In the aftermath of Comey’s appearance before the Senate Intelligence Committee on Thursday, the issue has been fully joined, and in all likelihood is being considered by the Justice Department’s special counsel, Robert Mueller. Indeed, it’s probably the most crucial question among the multitude Mueller is examining.

In two and a half hours of riveting sworn testimony, given a day after he had released a written “statement for the record” to the committee, Comey laid out a strong case for obstruction.

In sum, Comey said that Trump pressured him not only to drop the FBI’s criminal investigation of former national security adviser Michael Flynn, and but also to publicly exonerate Trump as a target of the bureau’s wider counterintelligence probe of Russian interference with the 2016 elections. After he declined to do either, and after he earlier refused to pledge personal loyalty to Trump, he was sacked on May 9. His testimony was watched by a combined TV audience of more than 19 million viewers.

As I recounted in my last column on the subject, on the day of Comey’s dismissal, the president claimed that he had acted pursuant to a Justice Department recommendation that Comey be released because of his inept handling of the investigation into Hillary Clinton’s use of a private email server during her tenure as secretary of state. But two days later, in a televised interview with NBC news anchor Lester Holt, Trump abandoned the pretense that Clinton’s emails had anything to do with canning Comey, acknowledging that he had terminated the director because of the “Russia thing,” which he insisted was a “made-up story.”

In the language of criminal law and procedure, Comey’s testimony on Thursday establishes a prima facie case of obstruction—that is, a showing of guilt which, standing alone, proves the essential elements of the crime.

Section 1505 of Title 18 of the U.S. Code of Laws makes it a felony to “corruptly” influence, obstruct or impede or attempt to influence, obstruct or impede” a federal proceeding. Other code sections proscribe the intimidation of witnesses in judicial, administrative and congressional proceedings. Violation of federal obstruction laws is punishable, in some instances, by prison sentences of up to 20 years.

Section 1515 of the code defines the intent required for an obstruction conviction as “acting with an improper purpose.” The intent element thus focuses on whether Trump dispatched Comey for the improper purpose of obstructing either the Flynn probe or the larger Russia inquiry.

However, like all prima facie cases, Comey’s testimony is only, as the literal Latin translation of the term indicates, “at first look.” Even if the testimony is technically sufficient to prove a case of obstruction, it would carry the day later in a court of law or an impeachment trial only if it isn’t subsequently rebutted by substantial contradictory evidence.

What, then, is Trump’s rebuttal, or defense?

Fortunately, we don’t have to speculate. Both Trump and his personal lawyer, New York attorney Marc Kasowitz, as well as numerous surrogates, have come forward with defenses. Unfortunately for Trump, however, the defenses proffered thus far range from unconvincing to side-splittingly absurd.

Let’s start with the ridiculous notion promoted by Trump surrogates, and in particular by House Speaker Paul Ryan, R-Wis., that Trump is a political novice and lacks the inside-the-Beltway experience to understand that his overtures to Comey about Flynn and Russia might have crossed important legal lines. “The president is new at this,” Ryan told reporters soon after Comey had finished testifying. “He’s new to government. And so he probably wasn’t steeped into the long-going protocols that established the relationships between DOJ, FBI and White Houses.”

As tempting as it may be to accept Ryan’s characterization of the leader of the free world as an ignorant boob beyond legal accountability, the effort is devoid of merit. Before imploring Comey to drop the Flynn probe on Feb. 14, Trump ordered both Attorney General Jeff Sessions and his son-in-law and top adviser Jared Kushner to leave the Oval Office—a clear sign that the president intended to say something especially sensitive for Comey’s ears only.

As political commentator Simon Maloy explained in a recent Rolling Stone post, Trump “forcefully attacked Bill Clinton for meeting briefly [and alone] with then-Attorney General Loretta Lynch while Hillary Clinton was under FBI investigation. … At the time, Trump seemed to grasp how ethically fraught it was for Bill Clinton and Lynch to even leave open the possibility that they had discussed an ongoing investigation into Hillary. ‘You see a thing like this and, even in terms of judgment, how bad of judgment is it for him or for her to do this?” Trump asked [at the time.]. ‘It’s so out of bounds.’ “

Nearly as absurd is the contention of former Harvard Law School professor Alan Dershowitz that Trump can’t be guilty of obstruction because he had the legal authority to fire Comey. Dershowitz’s position has been widely debunked by an array of legal scholars, including Harvard colleague Laurence Tribe, who has pointed out that while the president has the power to fire the director of the FBI, he cannot abuse that power. Clearly, if Trump fired Comey to derail or influence the course of the Russia investigation, he acted for an improper purpose, implicating himself in an obstruction of justice.

Also absurd is the notion that Trump can’t be guilty of obstruction because no hard evidence has been produced of collusion between him and Russia. In his online blog, Sidebars, George Washington University Law School professor Randall Eliason wrote last month: “Obstruction is a crime independent of the merits of any underlying case. Even if an investigation doesn’t result in criminal charges, you can get in trouble for obstructing that investigation—just ask Scooter Libby or Martha Stewart. As the old saying goes, sometimes the cover-up is worse than the crime.”

Nor can Trump and his supporters find comfort in the dubious argument that an FBI investigation isn’t technically considered a “proceeding” for purposes of the obstruction statutes, and as a result, obstruction laws don’t apply to Comey’s firing. Even if a court today were to hold that bureau probes don’t formally constitute “proceedings”—as a federal district judge so ruled in an obscure and often-criticized 1981 case—the argument that no obstruction occurred would fail because a federal grand jury in northern Virginia was already investigating Flynn at the time of Comey’s dismissal. Moreover, the Senate Intelligence Committee held its first hearing on alleged Russian meddling on Jan. 10. The House Permanent Select Committee on Intelligence opened its first probe on Jan. 23 and held its first hearing on the question on March 20. In any event, Trump knew that Flynn was under federal investigation long before Inauguration Day.

Mueller reportedly has taken charge of the Virginia grand jury. There can be no question that both the work of the grand jury and the congressional intelligence hearings are “proceedings” to which the obstruction laws apply. The FBI, as the Justice Department’s primary law-enforcement arm, plays a central role in providing evidence and information to both grand juries and congressional committees. It doesn’t take a genius to surmise that in firing Comey, Trump thought he could short-circuit the work of both the grand jury and Congress.

Also unavailing are the defenses and counterclaims asserted by Kasowitz. In a brief televised appearance Thursday at the National Press Club in Washington, D.C., Kasowitz read from a prepared statement, declaring that his client felt “completely vindicated” by Comey’s testimony. With all due respect, it’s difficult to see why.

Although it is true, as Kasowitz noted at the outset of his statement, that Comey confirmed that he had previously told Trump he was not under investigation in the Russia counterintelligence probe, Comey clarified in his Senate testimony that he did not know if the president was currently under investigation.

“Let’s turn our attention to the underlying activity at issue here: Russia’s hacking of those emails and the allegation of collusion. Do you think Donald Trump colluded with Russia?” Arkansas Republican Sen. Tom Cotton asked Comey.

“As I said,” Comey answered, “when I left, we did not have an investigation focused on President Trump. But that’s a question that will be answered by the [Mueller] investigation. …”

More importantly, absolving Trump in the counterintelligence probe would have no bearing on the obstruction issue. In this respect, Kasowitz elected, in effect, to accuse Comey of perjury, asserting that the president “never, in form or substance, directed or suggested that Mr. Comey stop investigating anyone, including suggesting that Mr. Comey ‘let Flynn go.’ ” Kasowitz similarly denied that Trump ever told Comey, “I need loyalty, I expect loyalty.”

Kasowitz also branded Comey a “leaker” for giving the contemporaneous and unclassified notes he had prepared of his Feb. 14 White House meeting with Trump (during which the president urged Comey to “let Flynn go”) to his friend, Columbia Law School professor Daniel Richman. The professor subsequently shared the content of the notes—but not the actual documents—with The New York Times. Kasowitz claimed the memos pertained to “privileged conversations,” and that they were leaked even before Comey was terminated. Late last week, Kasowitz followed up, threatening to file a complaint with the Justice Department regarding the leaked memos and lodging an objection to Comey’s testimony with the Senate judiciary and intelligence committees.

Although only Kasowitz and Trump know for certain why they’ve opted for such an aggressive tack, the president has never been known for gentility in the more than 4,000 lawsuits he’s brought and defended over the decades. Still, the positions taken by Trump and his lawyer are head-scratchers.

In fact, the first mention of the Comey memos by The New York Times occurred in a story published on May 16, a full week after Comey’s termination. There is no evidence the memos were leaked before Comey left government service.

Moreover, as a private citizen at the time of his most recent Senate testimony, Comey was no longer constrained by claims of executive privilege. He had the right to testify, and there is nothing illegal in a private citizen going public with personal and unclassified notes about conversations with the president. Rather than being decried as a leaker, Comey is more properly thought of as a whistleblower.

Turning to the matter of perjury, setting up a “he said/he said” contest with Comey appears the stuff of desperation. Whatever his faults, Comey has a sterling reputation for honesty. Trump, by contrast—well, let’s just say that there is a reason PolitiFact awarded him its grand 2015 award for “Lie of the Year” for the aggregate untruths he told in the early phases of his presidential campaign. Even Donald Trump Jr., in an interview on Saturday with Fox News, seemingly conceded that his father told Comey on Feb, 14 that he “hoped” Comey would back off on Flynn.

Both Donald Jr.—and more significantly, Idaho Republican Sen. James Risch—have focused on Trump’s use of the word “hope” to show that Trump never commanded Comey to derail the Flynn investigation, but merely articulated a wish that cannot be deemed a threat or an act of obstruction. Comey, by contrast, testified that he took Trump’s expression of hope as a direction and an order.

On the surface, Donald Jr. and Risch, a former prosecutor, appear quite possibly to have outlined a plausible line of defense. At the Senate hearing, Risch seemed to score points by asking Comey, “You don’t know of anyone that has ever been [charged] for hoping something, is that a fair statement?”

Comey, appearing at a loss, responded only, “I don’t as I sit here.”

It turns out, however, as reported by veteran New York Times correspondent Charlie Savage in a story on Thursday, at least three recent federal appellate decisions have held to the contrary of Risch’s line of cross-examination. The cases are U.S. v. Bedoy from the 5th U.S. Circuit Court of Appeals, decided in 2016; U.S. v. Johnson from the 4th Circuit, decided in 1995; and U.S. v. McDonald from the 8th Circuit, decided in 2008.

In the McDonald case, as Savage wrote, the 8th Circuit upheld a trial judge’s decision to impose a longer sentence on the defendant, who had committed a bank robbery, because the defendant had obstructed justice when he told his girlfriend, a potential witness, “I hope and pray to God you didn’t say anything about a weapon.” In the Johnson case, which dealt with a similar utterance of “hope” to a witness by the defendant, the court noted: “A threat to a potential witness is sufficient to warrant an enhancement [for obstruction] as long as the statement was intended to threaten, intimidate or unlawfully influence that person.”

We come, then, to the question of the hour: With Trump’s defenses failing, where does the obstruction probe go from here? The short answer is that it proceeds, full speed ahead.

The day after Comey’s Senate appearance, in a Rose Garden press conference held jointly with the president of Romania, Trump once again went rogue, declaring that he would “one hundred percent” be willing to testify under oath to refute Comey’s allegations. In particular, he denied asking for Comey’s loyalty or requesting that he drop the Flynn probe.

Here’s betting that Special Counsel Mueller takes him up on his offer to take the stand, but not before he subpoenas Donald Jr. and Eric and Ivanka Trump; Jared Kushner; Jeff Sessions; Paul Manafort; Carter Page; Michael Flynn; and many others, to be deposed under penalty of perjury. Mueller will also subpoena, as have the House and Senate already, any tapes Trump may have made of his chin-wags with Comey—the tapes he referred to in his infamous tweet of May 12.

In keeping with standard investigatory practices, Mueller will likely save his deposition of Trump for last—by which time the 45th president of the United States may be so entangled by his own inculpatory and prior inconsistent statements, and the evidence offered by others, that he may finally decide to keep his mouth closed and plead the Fifth. In this connection, it’s important to keep in mind that even if, as most scholars believe, a sitting president must be removed from office before he can be criminally prosecuted, the statute of limitations for returning an obstruction indictment is five years—which will not expire until after Trump finishes his first term, resigns or is impeached.

Think an indictment and an invocation of the Fifth won’t happen? You’re seeing the once-improbable scenario unfold piece by piece, day by day, one tweet and intemperate outburst at a time.