Almost 200,000 people in Pennsylvania are state-approved medical marijuana patients. But Pennsylvania has a zero-tolerance limit for THC which places these patients at the risk of a criminal law prosecution for driving under the influence.

Cannabis or marijuana is still a Schedule I controlled substance under federal law comparable to heroin or LSD. State law prohibits driving if there is any amount of a Schedule I controlled substance in the driver’s bloodstream. Despite this, marijuana may be used to treat almost two dozen ailments under Pennsylvania law and a state Department of Health program.

Small amounts of THC, the psychoactive compound in marijuana, can stay in a person’s blood for up to one month. Because of the state’s zero-limit, the law considers drivers under the influence even if they are not impaired or used marijuana days or weeks earlier.

Several medical marijuana patients were prosecuted for DUI in Pennsylvania, usually after police stopped them while they were driving. These drivers said that they provided information, such as their state-issued cannabis use cards, to the police because they thought it would prevent arrest for a serious charge.

Patient advocates argue that these actions provided grounds for an arrest or obtaining a urine test. Motorists faced DUI charges, loss of their driver’s license for one year, fines and even imprisonment.

Earlier this month, a bill was introduced in the state house to amend the state’s DUI law. If enacted, it would exempt marijuana used lawfully under Pennsylvania’s medical marijuana act.

Driving while impaired by marijuana would still be illegal like the prohibitions against driving while impaired by prescription drugs. Police now have protocols to prove driver impairment, according to the bill’s sponsor.

A similar bill was introduced in the state Senate last year. An organizer for the National Organization for the Reform of Marijuana laws said that it should contain standards for testing for impairment and how drivers prove they are patients.

An attorney may be able to assist drivers arrested for these charges. Legal representation can help assure that their rights are protected and that a strong defense is undertaken.