Story highlights Asha Rangappa: Trump "weighing in" on Don Jr.'s statement could help Mueller if he pursues obstruction of justice case

If the President really wants to stop Mueller, the best thing he can do is stop being a witness against himself, she writes

Asha Rangappa is an associate dean at Yale Law School. She is a former special agent in the FBI, specializing in counterintelligence investigations. The opinions expressed in this commentary are solely those of the author.

(CNN) President Trump is a defense lawyer's worst nightmare -- and a dream defendant for special counsel Robert Mueller. Revelations the President may have personally dictated a misleading statement given to The New York Times about his son's meeting with a Russian lawyer is the latest example why.

Despite the President's vexation at Mueller's investigation into possible ties between his campaign and Russia -- as well as the possibility that Mueller could pursue obstruction of justice charges against him personally -- Trump has not learned that the best way to slow Mueller down is to stop making the case for him.

The basis for any investigation into a potential obstruction of justice case, as it stands now, lies primarily with the President's firing of former FBI Director James Comey. However, that in and of itself is not a crime. What Mueller would need to prove if he ends up bringing a charge of obstruction is that the President acted with "corrupt" intent. That is, Mueller would have to find evidence the defendant "acted, at least in part ... with the purpose of accomplishing ... an unlawful end result."

In other words, Mueller would have to find that the reasons behind Trump's efforts to end the Russia investigation were ones he knew were wrong. Finding evidence of a defendant's state of mind is usually difficult, since the contents of thoughts are not ordinarily on display, and even federal prosecutors aren't mind readers.

This is where Trump's involvement in drafting Don Jr.'s statement comes into play. You see, a big problem for Mueller if he tries to prove obstruction of justice is that, well, Trump is the President. As such, he in theory has several constitutionally permissible reasons for firing Comey.

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