720 ILCS 5/31-4

(a) A person obstructs justice when, with intent to prevent the apprehension or obstruct the prosecution or defense of any person, he or she knowingly commits any of the following acts:

(1) Destroys, alters, conceals or disguises physical evidence, plants false evidence, furnishes false information; or (2) Induces a witness having knowledge material to the subject at issue to leave the State or conceal himself or herself; or (3) Possessing knowledge material to the subject at issue, he or she leaves the State or conceals himself; or (4) If a parent, legal guardian, or caretaker of a child under 13 years of age reports materially false information to a law enforcement agency, medical examiner, coroner, State's Attorney, or other governmental agency during an investigation of the disappearance or death of a child under circumstances described in subsection (a) or (b) of Section 10-10 of this Code. (b) Sentence.

(1) Obstructing justice is a Class 4 felony, except as provided in paragraph (2) of this subsection (b). (2) Obstructing justice in furtherance of streetgang related or gang-related activity, as defined in Section 10 of the Illinois Streetgang Terrorism Omnibus Prevention Act, is a Class 3 felony. (Source: P.A. 97-1079, eff. 1-1-13.)