"If we had confidence after a thorough investigation of the facts that the President of the United States did not commit obstruction of justice, we would so state. ... However, we are unable to reach that judgment."
That was special counsel Robert Mueller's blunt conclusion about whether President Donald Trump committed obstruction of justice. It's found early in Mueller's report of his 22-month investigation into potentially criminal aspects of Donald Trump's campaign and presidency.
Mueller's full report - submitted to the Department of Justice on March 22 and published online with redactions on April 19 - highlights 10 areas in which the president may have committed obstruction of justice. I've read this 400-page document closely, and judging as a law professor and former elected official, I find multiple episodes that describe possible crimes.
These include: firing FBI Director James Comey, who was overseeing an investigation into possible collusion between Trump's 2016 campaign and the Russian government; attempting to curtail the special counsel's investigation and fire Mueller; and making statements that could have discouraged former campaign aides from testifying truthfully.
After reviewing all Mueller's evidence, Attorney General William Barr determined that the president did not obstruct justice. But Mueller concluded that he could neither charge nor exonerate Trump, and indicated that Congress should consider the evidence.
Here's how lawmakers will determine whether Trump committed a crime.
1. Did Trump act 'corruptly'?
According to federal law, obstruction occurs when a person tries to impede or influence a trial, investigation or other official proceeding with threats or corrupt intent. Bribing a judge and destroying evidence are classic examples of obstruction.
Other actions may constitute obstruction, depending on the context. The law requires that there be both an intent to obstruct and that the subject acted, as Mueller writes, "in a manner that is likely to obstruct justice."
For example, when national security adviser Michael Flynn became a target in the FBI's investigation of Russian election interference, Trump on Feb. 14, 2017 held a private meeting with Comey in the Oval Office.
There, according to Comey, he said, "I hope you can see your way clear to letting this go, to letting Flynn go. He is a good guy. I hope you can let this go."
These episodes would constitute obstruction of justice if Trump pressured and then fired Comey for "corrupt" - meaning willfully improper - reasons, and if these actions were likely to impede the FBI's investigation.
2. Did Trump have criminal intent?
Determining intent is tricky for prosecutors. It requires them to make a subjective judgment about the suspect's state of mind.
If Trump fired Comey in an effort to prevent the FBI from discovering incriminating information about him or his campaign, that would be "corrupt."
Other reasons would not rise to the level of corrupt intent.
Mueller found that a key factor for Trump's dismissal of Comey appears to have been concern that the FBI's investigation was casting a cloud over his presidency and hurting his ability to govern. As president, Trump has the executive power to choose the FBI director he thinks is best suited to the job.
Congress will apply this "corrupt intent" standard to all the incidents of possible obstruction outlined in Mueller's report.
3. Was interference likely?
Assessing whether a given action is "likely" to interfere in an investigation is a more objective determination.
The Mueller report is unambiguous about the negative implications of Trump's discussion with Comey about "letting [Flynn] go."
"The circumstances of the conversation show that the President was asking Comey to close the FBI's investigation into Flynn," it reads, citing Trump's insistence on meeting alone with Comey as evidence that the president "did not want anyone else to hear" him requesting that a federal inquiry be terminated.
Mueller also concludes that Trump's expressions of "hope" would reasonably be understood as a directive when issued by a president to his subordinate.
4. Is the sum greater than its parts?
Sometimes a single action or statement that alone does not constitute an illegal act may demonstrate obstruction of justice when viewed alongside other incidents, because it creates a pattern of "corrupt" behavior.
Trump's behavior toward Comey, for example, looks most damning when viewed alongside his many efforts to block the special counsel's work.
Those include Trump's request to White House counsel Don McGahn to have Deputy Attorney General Rod Rosenstein fire Mueller. That happened in May 2017, once it became clear that the special counsel would be investigating Trump for obstruction of justice.
Trump also pushed former Attorney General Jeff Sessions to take charge of the Mueller investigation, from which he had previously recused himself citing conflict of interest, and asking Sessions to narrow its scope.
These episodes are just a few of the the dozen or so incidents that, together, indicate Donald Trump may have conspired to obstruct justice in 2017 and 2018.
5. Can obstruction occur if collusion didn't?
In defending the president, Attorney General Barr has pointed to one important factor: Mueller found insufficient evidence to conclude that Trump ever colluded with Russia, which would have been illegal.
Legally, however, obstruction can occur even in the absence of an underlying crime.
Trump could have interfered in the FBI and special counsel investigations not to protect himself from collusion charges but to avoid scrutiny of his financial relationships with Russia or to protect members of his family or inner circle.
Six Trump staffers were indicted during Mueller's investigation.
Trump's verdict will come in 2020
The president has celebrated the Mueller report's release as the end of federal investigations into his administration.
But congressional inquiries into the president are just beginning. And further investigation might find evidence of other kinds of presidential misconduct.
In his report, Mueller wrote that Congress may decide to apply obstruction statutes to the president "in accordance with our constitutional system of checks and balances and the principle that no person is above the law."
Committing obstruction of justice or other misconduct may constitute the kind of "high crime or misdemeanor" necessary to start impeachment proceedings. Several Democratic lawmakers have now called for impeachment. So far, however, House leadership shows little appetite for impeachment, which would need bipartisan support in the Republican-led Senate to succeed in removing Trump from office.
Absent irrefutable new evidence of criminality that changes the minds of Republican lawmakers and voters, the American public will render its verdict on Trump's presidency in November 2020.