Last verified: March 2026

OUI-Marijuana Under MGL Ch. 90 §24

Operating a motor vehicle under the influence of marijuana is prosecuted under MGL Chapter 90, Section 24 — the same statute used for alcohol-related OUI. The law does not distinguish between alcohol impairment and cannabis impairment in terms of penalties, procedure, or consequences. If convicted, you face the same license suspension, fines, and potential jail time as an alcohol OUI.

No Per Se THC Limit

Unlike Colorado (5 ng/mL threshold) or some other states, Massachusetts has no per se THC blood concentration limit. There is no number above which you are automatically presumed impaired. This means prosecutors must prove actual impairment through evidence beyond a blood test alone — a significantly higher bar than alcohol cases where a 0.08% BAC creates a legal presumption.

Commonwealth v. Gerhardt (2017)

The most important Massachusetts cannabis DUI case is Commonwealth v. Gerhardt, 477 Mass. 775 (2017). The Supreme Judicial Court ruled that:

• Field sobriety tests alone cannot prove marijuana impairment. The court found that standard field sobriety tests (walk-and-turn, one-leg stand, horizontal gaze nystagmus) were designed for alcohol impairment and have not been scientifically validated for cannabis.
• Officers can testify to observations — bloodshot eyes, odor of marijuana, slow reactions, erratic driving — but cannot offer the opinion that the driver "failed" field sobriety tests or was "impaired" based solely on those tests.
• Expert testimony may be required to link observed behavior to marijuana-specific impairment, particularly in cases without additional evidence of impaired driving.

The Gerhardt ruling made Massachusetts cannabis OUI prosecutions significantly more difficult. It effectively shifted the burden from mechanical test results to a comprehensive evidence picture.

How Enforcement Works

Post-Gerhardt, law enforcement builds cannabis OUI cases through multiple evidence streams:

• Driving behavior: Erratic driving, lane departures, delayed responses to traffic signals, and other observable driving impairment
• Officer observations: Bloodshot and glassy eyes, marijuana odor, slow speech, impaired coordination during the stop
• Drug Recognition Experts (DREs): Specially trained officers who conduct detailed 12-step evaluations including pulse, blood pressure, eye examinations, and divided-attention tasks
• Blood testing: If arrested, a blood draw may establish the presence and concentration of active THC (delta-9-THC), though this alone is not sufficient for conviction
• Statements and evidence: Admissions of use, cannabis found in the vehicle, and other circumstantial evidence

Lifetime Lookback for Prior Offenses

Massachusetts uses a lifetime lookback period for OUI priors. Unlike states that use a 5-year or 10-year window, every prior OUI conviction in your lifetime counts toward enhanced penalties. A first offense from 1990 still counts as a prior if you are arrested again in 2026. This makes repeat OUI charges in Massachusetts among the most severe in the country.

Penalties by Offense Number

First offense penalties include a fine of $500 to $5,000, up to 2.5 years in jail, and a 1-year license suspension. Alternative dispositions including probation and driver alcohol/drug education programs are available for first offenders.

Open Container and Transportation

Cannabis must be transported in a closed container in the trunk or an area not accessible to the driver and passengers. An open container of cannabis in the passenger area carries a $500 fine, separate from and in addition to any OUI charges.