Testing Drivers for Marijuana vs. Alcohol: What’s the Difference?

If you’re pulled over by police and asked to consent to blood or breath testing, you have a legal obligation to consent. But how do police officers test drivers for marijuana vs. alcohol?

In the state of Massachusetts, the possession of marijuana for those who are 21 years of age and above is legal. While there are certain provisions and limitations to possession and use–for example, you can only be in possession of up to one ounce at a time, and you can only use marijuana in your home, not in a public place–the recreational use of the drug is permitted. However, it is illegal to drive under the influence of marijuana. But enforcing this law has been difficult, as there is no surefire way to determine whether or not a driver is “under the influence” of the drug. Here’s an overview of what you need to know about testing drivers for marijuana vs. alcohol use in our state–

The Breathalyzer: Testing Drivers for Alcohol Consumption

The breathalyzer has a long history. Originally invented in the late 1800s, the modern-day, portable breathalyzer was first used to determine the BAC of drivers in the 1950s. Because alcohol only stays in the bloodstream for a relatively short amount of time, if the results of a breathalyzer show that a person has alcohol in their system, officers (and the prosecution) can safely assume that the alcohol was imbibed within the past few hours or less. 

The same is not true for marijuana.

Testing Drivers for Marijuana Use

Unlike alcohol, which metabolizes fairly quickly, marijuana can stay in a person’s system for weeks, and is usually detectable in bodily fluids for between one and 30 days after use. As such, if someone is stopped and asked to consent to blood testing for marijuana, they may test positive even if the use of marijuana was legal. For example, a driver who is suspected of driving while under the influence of marijuana may test positive for the drug because they consumed it last week, not in the hours prior to driving.

So, how can recent cannabis use be detected?

Breakthroughs in Technology

Scientists have been hard at work to develop marijuana-testing technology that would function similar to a breathalyzer. The technology, as described in an article in CBS58, will be able to detect the amount of THC–the active ingredient in marijuana that provides the “high”–on the breath. According to the article, THC only lingers on the breath for about two-three hours after use. The technology could be making it to market within a year, according to reports. 

For now, though, there is no accurate way to determine whether a driver has used marijuana prior to driving, as even roadside sobriety tests can be inaccurate for numerous reasons, including that the effects of marijuana aren’t as well understood as are the effects of alcohol.

Have You Been Charged with Impaired Driving? Call Our DUI Defense Attorney Today

If you have been charged with driving impaired as a result of marijuana use, the prosecution has the burden to prove your guilt beyond a reasonable doubt. At The Law Office of Paul R. Moraski, our experienced DUI defense lawyer can poke holes in the prosecution’s argument, ensure that any evidence unlawfully obtained isn’t used against you, and advocate for your interests. Send us a message online or call us at (978) 397-0011 today for the legal help you need.