Missouri Drug Laws: Penalties, Charges & Treatment Options

Under RSMo § 579.015, it is unlawful for any person to possess or have under his or her control a controlled substance. Possession of any controlled substance except 35 grams or less of marijuana or any synthetic cannabinoid is a Class D felony, punishable by up to 7 years imprisonment and fines up to $10,000. Possession of more than 10 grams but not more than 35 grams of marijuana is a Class A misdemeanor (up to 1 year, $2,000 fine). Possession of 10 grams or less of marijuana is a Class D misdemeanor (fine up to $500). Note that under Amendment 3 (Article XIV, Missouri Constitution), adults 21 and older may legally possess up to 3 ounces of marijuana, so these criminal penalties apply primarily to amounts exceeding legal limits or to individuals under 21. For prior and persistent offenders, penalties may be enhanced to the next higher felony class under RSMo § 558.016.

RSMo § 579.015

https://revisor.mo.gov/main/OneSection.aspx?section=579.015

Driving While Intoxicated (DWI) — RSMo § 577.010

Missouri prosecutes drug-impaired driving under RSMo § 577.010. A person commits the crime of driving while intoxicated if they operate a motor vehicle while in an intoxicated or drugged condition. Under RSMo § 577.001, 'intoxicated condition' is defined as being under the influence of alcohol, a controlled substance, or drug, or any combination thereof. Unlike alcohol (which has a 0.08% BAC threshold), there is no specific nanogram threshold for drugs — any impairment from a controlled substance can support a DWI charge. Missouri uses the term DWI (Driving While Intoxicated) rather than DUI.

• First DWI offense — Notes: Probation typically available for first offenders
  Classification: Class B Misdemeanor
• Second DWI offense (Prior Offender) — Notes: Mandatory 10 days jail or DWI court program or 30 days community service
  Classification: Class A Misdemeanor
• Third DWI offense (Persistent Offender) — Notes: Mandatory 30 days jail or DWI court program or 60 days community service
  Classification: Class E Felony
• Fourth DWI offense (Aggravated Offender) — Notes: Mandatory 60 days before probation or parole eligibility
  Classification: Class D Felony
• Fifth or subsequent DWI (Chronic Offender) — Notes: No probation until 2 years served
  Classification: Class B Felony
• DWI causing death (Involuntary Manslaughter) — Notes: Can be charged as Class B felony (5-15 years) under aggravating circumstances
  Classification: Class C Felony

Missouri has an implied consent law under RSMo § 577.020. Refusal to submit to chemical testing results in a 1-year revocation of driving privileges. A second or subsequent refusal within 5 years is grounds for a Class A misdemeanor charge.

Despite recreational marijuana legalization under Amendment 3, driving while impaired by marijuana remains illegal under RSMo § 577.010. Missouri does not have a specific THC nanogram threshold; impairment is determined by officer observations, field sobriety tests, and drug recognition expert evaluations.

RSMo § 577.010; RSMo § 577.001

https://revisor.mo.gov/main/OneSection.aspx?section=577.010

Missouri provides broad naloxone access through RSMo § 195.206, which authorizes the Director of the Missouri Department of Health and Senior Services (DHSS) to issue a statewide standing order for opioid antagonists, including naloxone (Narcan). This standing order permits pharmacists to dispense naloxone without an individual prescription to anyone at risk of an opioid overdose or to a family member, friend, or other person in a position to assist someone at risk. Any person who administers naloxone in good faith to someone experiencing an opioid overdose is immune from civil and criminal liability. Missouri law also allows community organizations, first responders, and harm reduction programs to distribute naloxone.

RSMo § 195.206; RSMo § 195.205

Missouri DHSS Standing Order for Naloxone; Missouri Opioid-Heroin Overdose Prevention and Education (MO-HOPE) Project

Missouri has an extensive treatment court system, with over 140 treatment courts operating across the state. Drug courts provide an alternative to traditional criminal prosecution for eligible defendants with substance use disorders. Participants undergo court-supervised treatment programs typically lasting 12-18 months, which include regular drug testing, counseling (individual and group), community service, and regular appearances before a Drug Court judge or commissioner. Upon successful completion, charges may be dismissed or reduced. Missouri also operates DWI courts, juvenile drug courts, family drug courts, and veterans treatment courts. The Missouri Association of Treatment Courts (MATC) coordinates training and standards for these programs.

Available in most judicial circuits across Missouri; over 140 treatment courts statewide including adult drug courts, DWI courts, juvenile drug courts, family drug courts, and veterans treatment courts.

RSMo Chapter 478; Missouri Treatment Court Standards (June 2019)

Generally limited to nonviolent drug or alcohol offenders. Specific eligibility criteria are determined by each judicial circuit. First-time offenders and those whose criminal conduct was primarily motivated by addiction are prioritized.

https://www.courts.mo.gov/page.jsp?id=271

Missouri imposes mandatory minimum sentences for certain drug offenses, particularly trafficking charges. Under Missouri's felony classification system (RSMo § 558.011), Class A felonies carry a mandatory minimum of 10 years (up to 30 years or life), and Class B felonies carry a mandatory minimum of 5 years (up to 15 years). However, Missouri courts retain significant discretion through the ability to suspend imposition of sentence (SIS) for many drug offenses. When a court suspends imposition, the defendant is placed on probation, and upon successful completion, the case may be dismissed without a conviction on record. This option is generally not available for Class A felony drug trafficking convictions. For chronic DWI offenders (5th+ offense), a mandatory minimum of 2 years imprisonment applies before eligibility for probation or parole.

Suspended Imposition of Sentence (SIS) is available for most drug offenses below Class A felony level, giving judges discretion to avoid mandatory prison time.

RSMo § 558.011; RSMo § 579.065; RSMo § 577.023

Missouri provides several treatment alternatives to incarceration for drug offenders. Drug courts are the primary diversion mechanism, offering court-supervised treatment as an alternative to prosecution. Missouri courts can also suspend imposition of sentence (SIS) and place defendants on probation with treatment conditions. The state funds substance abuse treatment through the Missouri Department of Mental Health (DMH) Division of Behavioral Health, which contracts with community providers for outpatient, intensive outpatient, and residential treatment services. The Missouri Reentry Process provides transition planning and treatment connections for individuals re-entering the community from incarceration.

• Drug Court / Treatment Court Programs
  Description: Court-supervised treatment programs lasting 12-18 months with graduated sanctions and incentives, regular drug testing, counseling, and judicial monitoring. Successful completion can result in charge dismissal.
• Suspended Imposition of Sentence (SIS)
  Description: Courts may suspend imposition of sentence and place defendants on probation with mandatory treatment conditions. Upon successful completion, the case is dismissed without a conviction of record.
• DMH Division of Behavioral Health Treatment Services
  Description: State-funded substance abuse treatment services including outpatient, intensive outpatient, residential, and medication-assisted treatment (MAT) through community providers across Missouri.
• Missouri Reentry Process
  Description: Comprehensive reentry planning for incarcerated individuals including substance abuse treatment referrals, employment assistance, and community support connections upon release.

RSMo Chapter 478; RSMo § 557.011; RSMo Chapter 630

2022: Missouri voters approved Amendment 3 on November 8, 2022, legalizing recreational marijuana for adults 21+ under Article XIV of the Missouri Constitution. The amendment took effect December 8, 2022, allowing personal possession of up to 3 ounces and home cultivation of up to 6 flowering plants.

2023: Recreational marijuana sales began February 3, 2023. The automatic expungement process for prior nonviolent marijuana convictions commenced, with misdemeanor marijuana offenses required to be expunged by June 2023 for eligible individuals. The 6% state excise tax on recreational sales went into effect.

2023-2024: Over 140,000 marijuana-related criminal records were expunged under Amendment 3's automatic expungement provisions. Micro-license applications for new cannabis businesses were processed through a lottery system, expanding market access beyond existing medical dispensaries.

2025: The Missouri Supreme Court issued a ruling narrowing the pool of marijuana offenses eligible for expungement, clarifying that only convictions involving 3 ounces or less of cannabis qualify for automatic expungement relief under Amendment 3.