In weighing whether President Donald Trump obstructed justice in the Russia investigation, Special Counsel Robert Mueller III and his team parsed rulings by a U.S. Supreme Court that is increasingly skeptical of the broad wording of obstruction laws and their use by federal prosecutors.

Mueller declined to reach a conclusion on obstruction after examining the evidence and relevant court decisions.

“The evidence we obtained about the president's actions and intent presents difficult issues that would need to be resolved if we were making a traditional prosecutorial judgment,” Mueller's team said. “At the same time, if we had confidence after a thorough investigation of the facts that the president clearly did not commit obstruction of justice, we would so state. Based on the facts and the applicable legal standards, we are unable tp reach that judgment.”

Mueller's team added: “Accordingly, while this report does not conclude that the president committed a crime, it also does not exonerate him.”

Still, U.S. Attorney General William Barr, working with his deputy, Rod Rosenstein, concluded that the evidence Mueller marshaled did not amount to obstructive acts by Trump.

The report presented 10 episodes that Mueller and his team examined. They included the firing of FBI Director James Comey; efforts to remove Mueller; attempts to get then-Attorney General Jeff Sessions to “unrecuse” himself from the Mueller investigation; and comments and conduct toward Michael Cohen and Paul Manafort.

Mueller did not pursue a subpoena against Trump for his testimony, saying that such a move would create “substantial delay” in the investigation. Mueller's team disagreed with Trump's attorneys that the president is shielded from obstruction-of-justice laws. The Constitution does not “categorically and permanently immunize a President for obstructing justice,” the Mueller report said.

Mueller analyzed Trump-related evidence under the three statutory obstruction-of-justice elements: obstructive act, nexus to a proceeding and intent. Here's a look at how Supreme Court cases factored into the review.

>> Obstructive acts: Marinello v. United States (2018). Mueller looked to a high court decision from last term—Marinello v. United States—for insight on the definition of obstructive act.

In the Marinello case, a 7-2 majority rejected the Trump Justice Department's reading of an omnibus obstruction clause in the Internal Revenue Code. The verbs “obstruct or impede” are broad, the report said, “and can refer to anything that blocks, makes difficult, or hinders.”

“Regardless, to rely upon prosecutorial discretion to narrow the otherwise wide-ranging scope of a criminal statute's highly abstract general statutory language places great power in the hands of the prosecutor,” Justice Stephen Breyer wrote for the majority. “Doing so risks allowing 'policemen, prosecutors, and juries to pursue their personal predilections.'”

>> Nexus to an official proceeding: United States v. Aguilar (1995); Arthur Andersen v. United States (2005). Obstruction of justice law, Mueller's report said, generally requires a nexus or connection to an official proceeding. Mueller cited Aguilar for the requirement that the nexus must be to pending “judicial or grand jury proceedings.” The nexus also can include a connection to a “pending” federal agency proceeding, or a congressional inquiry or investigation.

But under the Aguilar and Andersen rulings, the report stated, the government must demonstrate “a relationship in time, causation, or logic” between the obstructive act and the proceeding or inquiry to be obstructed. The nexus requirement, as articulated in the Aguilar ruling, narrows the scope of obstruction statutes to ensure that individuals have “fair warning” of what the law proscribes, the report stated.

In Aguilar, an 8-1 majority, led by Chief Justice William Rehnquist, reversed the conviction of U.S. District Judge Robert Aguilar for obstruction of justice. The majority held that someone who attempts to obstruct a grand jury proceeding by making  false or misleading statements to prospective witnesses can't be prosecuted for obstruction.

>> Corrupt intent: United States v. Aguilar (1995) and Arthur Andersen v. United States (2005). Mueller's prosecutors returned to the Aguilar and Andersen decisions for analysis on “corrupt intent.”

The special counsel's report stated that the word “corruptly” provides the intent element for obstruction and means acting “knowingly and dishonestly” or “with an improper motive.'” Mueller cited to Andersen, too, which interpreted “corruptly” to mean “wrongful, immoral, depraved, or evil” and which held that acting “knowingly … corruptly” requires “consciousness of wrongdoing.”

Justice Antonin Scalia (2010) Photo by Diego M. Radzinschi/ALM

Mueller's report at one point referred to Ballentine's Law Dictionary for what is required to show a person has acted with intent: to obtain an “improper advantage for himself or someone else, inconsistent with official duty and rights of others.” It also cited the late Justice Antonin Scalia's concurring and dissenting opinion in Aguilar. Scalia characterized that dictionary's definition as the “longstanding and well-accepted meaning” of “corruptly.”

In Arthur Andersen, the Supreme Court unanimously reversed the conviction of the accounting firm for obstructing an official proceeding by ordering the destruction of documents. A key issue at the firm's trial was whether it had acted “corruptly.” In an opinion by Rehnquist, the justices held that the jury instructions improperly conveyed the elements of “corrupt persuasion” under the relevant statute.

“Only persons conscious of wrongdoing can be said to 'knowingly … corruptly persuad[e],'” Rehnquist wrote. “And limiting criminality to persuaders conscious of their wrongdoing sensibly allows §1512(b) to reach only those with the level of 'culpability … we usually require in order to impose criminal liability.'”