President Trump didn't collude with Russia and he sincerely thought the investigation on the matter was a politically motivated witch hunt. This is Attorney General William Barr's explanation of why Trump wasn't obstructing justice when he took actions that could have interfered with the investigation at this morning's press conference.

Some explanation: Mens rea, a Latin term meaning knowledge of wrongdoing, is central to any consideration of criminal conduct. The same action could be legal or illegal depending on whether it was taken with corrupt intent or not.

Barr on Thursday morning suggested that the Justice Department weighed whether President Trump acted with mens rea in concluding that Trump didn't obstruct justice.

"In assessing the President’s actions discussed in the report," Barr said, "it is important to bear in mind the context."

"There was in fact no collusion," Barr said. "And as the Special Counsel’s report acknowledges, there is substantial evidence to show that the President was frustrated and angered by a sincere belief that the investigation was undermining his presidency, propelled by his political opponents, and fueled by illegal leaks.... Apart from whether the acts were obstructive, this evidence of non-corrupt motives weighs heavily against any allegation that the President had a corrupt intent to obstruct the investigation."

For instance, firing James Comey could have been obstruction of justice if Trump was doing it to keep his collusion secret. But under Barr's explanation, Trump may have fired Comey because he thought Comey was waging a political witch hunt. That's a non-corrupt motive.