Under Tennessee's DUI law you can be charged with a DUI or drugged driving if you are under the influence of marijuana. How does the police determine if you're too stoned to drive? The Marshall Project recently examined that same question but on a national scale.
How does the police determine if your too high or stoned to drive? Tennessee, as well as 12 other states, make it illegal to have any amount of marijuana in your bloodstream. In some states like Colorado, it is 5 nanograms per milliliter of blood. It varies from state to state. Tennessee DUI laws are more sensible in that it also defines intoxication.
The tricky part is whether routine field sobriety tests can determine if you are impaired by marijuana. From the research on the standardized field sobriety tests, no research was done on marijuana only alcohol. Police are starting to have police officers trained as drug recognition experts. Here is an excerpt of the Marshall report article on drug recognition experts commonly referred to as a DRE.
"Some police departments use drug recognition experts, specially trained officers dispatched to evaluate suspected drugged drivers. Commonly referred to as DREs, these officers use an hour-long 12-step process, including taking the suspect's blood pressure and pulse, conducting several eye exams and balance tests, to generate an opinion about whether the driver is intoxicated, and, if so, by what. Preliminary research seems to indicate their opinions are of mixed quality, and not all judges allow DREs to testify to their findings. "They're not EMTs. They're not medically trained," says Lovrich, the Washington State University professor, who, in a recent study of five years of DRE data in Washington and New Mexico, found a false-positive rate for pot intoxication ranging from 38 percent to 68 percent. "Everyone in the DRE business knows it's really hard to do this."
The National Highway Safety and Traffic Administration has produced a guide on drugs and human performance. According to their findings, 'it is difficult to establish a relationship between a person's tetrahydrocannabinol (THC) blood or plasma concentration and performance impairing effects.'
If the government can't determine what driving under the influence of marijuana, how can the police or a jury do it?