As I’ve mentioned in past posts, there are a number of problems with trying to determine whether a driver is under the influence of marijuana. See, for example, Marijuana-Impaired Driving: A Prosecutor’s Nightmare?, New Study: Minimal Driving Impairment From Marijuana, California Proposes New Law to Allow Roadside Marijuana Tests, Is a Marijuana Breathalyzer in the Offing? Primary among these problems are:
1. Marijuana cannot be detected or measured on a breath machine. It can be measured with blood tests, but there is almost always a delay — often hours — in obtaining a blood sample. Result: due to continuing metabolism of marijuana in the body, the level at the time of testing may be significantly higher or lower than at the time of driving
2. Unlike alcohol which dissipates after several hours, THC (the active ingredient in marijuana) can stay in a person’s system for days or even weeks after smoking or eating. Even though they are no longer affecting the driver, they will be still detected and reported as marijuana in the blood.
3. There are no recognized scientific studies establishing at what level of THC in the blood a person’s driving ability is impaired.
A solution to one of these problems would be the development of a breath machine which could accurately measure marijuana on the breath — particularly if this could be done quickly at the scene of the arrest. But no such device exists….yet:
Marijuana Breathalyzers to Test California Pot Users for Pot Use
Los Angeles, CA. Sept. 14 – An Oakland-based company has developed a marijuana breathalyzer for distribution across police stations in the U.S. to begin a nationwide test to see if they can monitor people operating motor vehicles while under the influence of pot, and drivers in California were among the first to be tested…
The marijuana breathalyzer – which had some help in development by the University of California’s chemistry department – is able to detect THC on people’s breath after they’ve consumed edible pot products as well as alcohol.
Hound Labs plans to roll their product out nationwide upon further testing to validate the technology’s results.
Until it’s perfected, police will have to continue relying on testing saliva, urine, and blood to measure marijuana in the system, which can show the presence of drugs days after the user is actually under the influence.
Some police have already shown their support for the breathalyzer, including Lompoc Police Chief Patrick Walsh, who says he plans on issuing the device to at least six of his departments over the next six months…
Ok, so maybe they will be able to detect and even measure the amount of THC in the blood from testing the breath. But how does this solve the problem of inactive THC still remaining in the blood from smoking days or weeks earlier? And what good is it to know the amount of THC in the breath if there is still no scientific evidence of the amount necessary to impair driving ability?