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.