(1) Except as authorized by part 1 or 3 of article 280 of title 12, part 2 of article 80 of title 27, section 18-1-711, section 18-18-428(1)(b), or part 2 or 3 of this article 18, it is unlawful for a person knowingly to possess a controlled substance.

(2) On or after March 1, 2020, a person who violates subsection (1) of this section by possessing:

(a) Any material, compound, mixture, or preparation that contains any quantity of flunitrazepam; ketamine; gamma hydroxybutyrate, including its salts, isomers, and salts of isomers; cathinones; or more than four grams of a controlled substance listed in schedule I or II of part 2 of this article 18 commits a level 4 drug felony.

(b) Deleted by Laws 2013, Ch. 333, § 8, eff. Oct. 1, 2013.

(c) Any material, compound, mixture, or preparation that contains not more than four grams of a controlled substance listed in schedule I or II of part 2 of this article 18 or any quantity of a controlled substance listed in schedule III, IV, or V of part 2 of this article 18 except flunitrazepam, gamma hydroxybutyrate, or ketamine commits a level 1 drug misdemeanor; except that a fourth or subsequent offense for a violation of this subsection (2)(c) is a level 4 drug felony.

(3) If the circumstances described in section 18-18-428(1)(b) occur, the peace officer shall not arrest the person pursuant to this section for any minuscule, residual controlled substance that may be present in the used hypodermic needle or syringe, and the district attorney shall not charge or prosecute the person pursuant to this section for any minuscule, residual controlled substance that may be present in a used hypodermic needle or syringe. The circumstances described in section 18-18-428(1)(b) may be used as a factor in a probable cause or reasonable suspicion determination of any criminal offense if the original stop or search was lawful.

(4) Notwithstanding the provisions of subsection (2) of this section, on or after March 1, 2020, a district attorney shall not charge or prosecute a person pursuant to this section for any minuscule, residual, or unusable amount of a controlled substance that may be present in a used hypodermic needle or syringe, or other drug paraphernalia, as defined in section 18-18-426. The circumstances described in this subsection (4) may be used as a factor in a probable cause or reasonable suspicion determination of any criminal offense if the original stop or search was lawful.

(5) Notwithstanding any provision of this section, a person may be charged with any other offense in this article 18, including unlawful distribution, manufacturing, dispensing, or sale of a controlled substance, or possession with intent to do the same, pursuant to section 18-18-405, when there is evidence for the person to be so charged. Such evidence may include, but is not limited to, the amount of the controlled substance that the person possesses.