Nearly half of all states have legalized marijuana (or marijuana-derived products) for medicinal use, including New York. This has reduced the vast number of individuals prosecuted each year for non-violent drug offenses. But it has also led to confusion and legal snags.
Marijuana is still illegal under federal law. And in states where it is legal, legislators and police departments are trying to figure out how to effectively fight drugged driving.
First of all, the mere presence of THC in the blood does not prove that someone is high. THC can be detected and measured in blood tests. But THC tends to stay in a person's body long after the high/impairment has worn off. This means that someone arrested for suspected drugged driving could be charged despite not being at all impaired.
Second, being high on marijuana is hard to quantify. Drugs affect each person differently, based on factors such as their body size, tolerance and history of use. One person with high levels of THC in their blood is not necessarily more impaired than someone with lower levels of the chemical. Some states have tried to set legal thresholds for impairment (5 nanograms in Colorado), but these thresholds were arbitrarily chosen.
Finally, there are no reliable tools for conducting roadside impairment tests. Breathalyzers can detect the level of alcohol in a person's body quickly and accurately (most of the time). But there is no such device to test marijuana levels. It can take up to two hours for police to obtain a warrant for a blood test, by which time THC levels may have dropped considerably.
Recently, auto club AAA released the results of a study arguing that there is no scientific evidence to support the marijuana impairment laws some states have adopted. Because of this, unimpaired drivers have likely been prosecuted due to fact that they had lingering THC in their blood.
Most Americans agree that the legalization of medical marijuana is humane, and that legalization of recreational marijuana is a practical necessity considering just how many people use the drug. While we continue to face the bumps and hurdles caused by pot's changing legal status, we need to ensure that innocent people are not being convicted of crimes based on arbitrarily chosen standards.