While driving under the influence of marijuana is illegal in Virginia, there is no comprehensive system that allows officers to test motorists reliably when out on the road. However, scientists are making progress when it comes to developing a portable marijuana "Breathalyzer".
Drivers can have some alcohol in their system without being too impaired to legally drive, but no amount of marijuana is legal while driving in any state. However, there is no current roadside test to detect marijuana on someone's breath. Finding compounds that relate to marijuana use is more difficult than finding alcohol in a driver's system, but researchers at the National Institute of Standards and Technology may have figured out how to measure THC, which is one of the main psychoactive compounds in marijuana.
The scientists measured the compound's vapor pressure, which corresponds to what happens when a substance changes from liquid to gas. When a molecule leaves the blood and is exhaled through breath, vapor levels can measure the amount of a substance in the blood. The researcher's findings were published in 'Forensic Chemistry" on June 27. The work done by these scientists makes the possibility of a portable marijuana testing device more likely. However, more study is required to understand how TCH levels in the breath correlate with blood levels.
While it is unclear how exactly portable marijuana tests will work, the rules concerning law enforcement are clearer. When pulling a driver over, an officer must explain why he or she stopped a vehicle. Authorities are required to have a reasonable suspicion that some law has been broken when making a traffic stop. One defense that attorneys could raise to combat drunk driving charges was that the stop itself was not proper.