"Obstruction of justice is defined in the omnibus clause of 18 U.S.C. § 1503, which provides that "whoever . . . . corruptly or by threats or force, or by any threatening letter or communication, influences, obstructs, or impedes, or endeavors to influence, obstruct, or impede, the due administration of justice, shall be (guilty of an offense)." Persons are charged under this statute based on allegations that a defendant intended to intefere with an official proceeding, by doing things such as destroying evidence, or intefering with the duties of jurors or court officers."
"A person obstructs justice when they have a specific intent to obstruct or interfere with a judicial proceeding. For a person to be convicted of obstructing justice, they must not only have the specific intent to obstruct the proceeding, but the person must know (1) that a proceeding was actually pending at the time; and (2) there must be a nexus between the defendant’s endeavor to obstruct justice and the proceeding, and the defendant must have knowledge of this nexus.
§ 1503 applies only to federal judicial proceedings. Under § 1505, however, a defendant can be convicted of obstruction of justice by obstructing a pending proceeding before Congress or a federal agency. A pending proceeding could include an informal investigation by an executive agency." Cornell Law
It is the italicized portion of the definition that puts Trump in trouble. As facts start to surface, it appears that Trump is taking action to obstruct a pending proceeding with a federal agency, The FBI. There also is the potential that his actions also are obstructing a Congressional proceeding. Although some of the reported conduct may fit the definition overall, the reported conduct does fit the italicized portion of the definition cited above, which is the easier to prove as it has a broader scope.
The nation’s top intelligence official told associates in March that President Trump asked him if he could intervene with then-FBI Director James B. Comey to get the bureau to back off its focus on former national security adviser Michael Flynn in its Russia probe, according to officials. The Washington Post
If this proves to be true, this action fits the definition of obstruction. Trump is taking action to obstruct a federal agency, The FBI, from conducting an investigation. The simple rule, don't ask anyone to get the FBI Director to back off a pending investigation.
The facts surfacing, if ultimately proven, get more disturbing on obstruction:
On March 22, less than a week after being confirmed by the Senate, Director of National Intelligence Daniel Coats attended a briefing at the White House together with officials from several government agencies. As the briefing was wrapping up, Trump asked everyone to leave the room except for Coats and CIA Director Mike Pompeo.
The president then started complaining about the FBI investigation and Comey’s handling of it, said officials familiar with the account Coats gave to associates. Two days earlier, Comey had confirmed in a congressional hearing that the bureau was probing whether Trump’s campaign coordinated with Russia during the 2016 race. The Washington Post
The actions also fit well with the definition of obstruction.
There are other developing facts that should cause concern. If Trump met privately with James Comey and asked, or suggested, that Comey "back off" then that action can fit into the definition as it is easily interpreted as an act of obstruction.
If Comey's subsequent firing is proven to be related to Trump's efforts as described in this post, that firing also fits into the obstruction definition.
These reports are troubling. They warrant extensive investigation. If proven to be true, the facts will warrant impeachment.