Imagine being charged with Driving under the influence (DUI), days or weeks after the last time you smoked cannabis. This is the reality that many users face in Pennsylvania, where DUI guidelines allow for arrests based on a “zero tolerance” concept. These outdated laws result in the conviction of drivers that cannot be proven impaired while driving.

The legal idea of marijuana creates a stigma of drug abuse, which allows out-of-date laws to remain effective. Under federal law, marijuana is a Schedule 1 drug, alongside Lysergic acid diethylamide (LSD), cocaine, ecstasy, methaqualone (Quaalude), and peyote. The Drug Enforcement Administration (DEA) defines drugs in this category as having a high potential for abuse, and no currently accepted medical use. Though society attitudes are evolving to accept the proven medicinal qualities of cannabis, many laws have yet to change.

In Pennsylvania and six other states, drivers found with any trace of a Schedule 1 drug in their blood are charged with DUI. First time controlled substance DUI in Pennsylvania carries a fine of up to $5,000, and six months in jail.

These zero tolerance guidelines created a brutal reality for Elizabeth Mason, a Pennsylvania resident who was 21 years old at the time of her arrest.

From Bad to Worse

It was a warm February day when Mason was taking a drive with her daughter. As her child babbled from her car seat, Mason took her eyes off the road to smile at her daughter. Unfortunately, this act caused her to veer to the right, taking two tires off the pavement.

As Mason tried to correct her mistake, she lost control of the vehicle. The young mother’s car hit an embankment, and rolled once before coming to rest, sideways, in a deep ditch. This is where Mason unbuckled her suspended toddler from the car, after narrowly avoiding injuries.

Mason flagged down a passing motorist who called 911, sending emergency services to the scene. Emergency medical technicians (EMTs) discovered a marijuana pipe in the wreckage, leading police to conduct an inconclusive field sobriety test. Mason told the investigating officer that she had not smoked that day, and explained why the crash occurred. Police remained unsure.

The responding officer allowed Mason to accompany her daughter in the ambulance, under the condition that she provide a blood sample upon arrival to the hospital. Mason agreed, knowing there would be Tetrahydrocannabinol (THC) in her system from regular use. Mason was hoping that her cooperation and honesty would lessen the risk of being charged for this accident.

Mason was very wrong.

The blood test Mason consented to predictably revealed a small amount of THC: four Nanograms per milliliter (ng/mL). As a result, she faced DUI, Child Endangerment, and Possession of Drug Paraphernalia. The District Attorney also charged her with Possession of a Controlled Substance, due to the resin in her pipe.

Mason was later convicted and sentenced to serve 10 days in county jail, 18 months on parole, and 12 more months on probation. Mason also owed over $4,000 in fines, on which she is still paying.

It took one moment for the life of this caring mother to be physically and emotionally flipped on its side, though her blood test could not prove that cannabis was the cause of her accident.

No Test Can Prove Impairment

In an American system where suspects are presumed innocent, it is up to the prosecutor to prove guilt with hard evidence. Pennsylvania’s zero tolerance guidelines allow a guilty verdict with any trace of THC in a suspect’s blood.

THC, the psychoactive element in cannabis, remains in the body for up to 30 days after consumption. Blood tests detect THC for seven days or more, well after the high fades. This simple, well-known fact leaves anyone who smokes at risk for DUI within that time frame.

A July 2017 National Highway Traffic Safety Administration report to Congress shows that cannabis can impair driving for three hours after use, yet there are no evidence-based standards to accurately detect marijuana-impaired driving. Currently, police officers use a series of cues and symptoms to assume the impairment of a driver.

Unfortunately, this method has an extremely high false-positive rate.

Due to the lack of chemical tests that can show the level of driver impairment, new methods must be developed. The National Highway Traffic Safety Administration suggests that an onsite test to evaluate behavior and cognition may help determine if a suspected driver is actually impaired at the time of arrest.

With Pennsylvania’s budding medical marijuana program, lawmakers must reshape DUI laws. Development of standards and awareness is necessary to avoid convicting innocent drivers while also accommodating medical cannabis patients. It is important that lawmakers compassionately evaluate existing laws and reach a conclusion that makes sense.


California NORML. (n.d.). Marijuana Drug Test Detection Times. Retrieved from

Commonwealth of Pennsylvania. (2018). Guide: Getting Medical Marijuana. Retrieved from

Compton, R. (2017, July). Marijuana-Impaired Driving -A Report to Congress. (DOT HS 812 440). Washington, DC: National Highway Traffic Safety Administration. Retrieved from

PennDOT Driver &Vehicle Services. (n.d.). DUI Legislation. Retrieved from

The Drug Enforcement Agency. (n.d.). Drug Scheduling. Retrieved from


Sarah Welch
Sarah Welch is a professional freelance content writer, blogger, and cannabis enthusiast from Pennsylvania. She is passionate about sharing in-depth knowledge while entertaining her readers and providing a voice for cannabis users everywhere. Be sure to check out her work at Sarah Welch Writing and connect with her on Twitter.
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