Recreational and medical marijuana are becoming increasingly common throughout the country, as more states pass statutes allowing it in certain instances. This includes Colorado, California and Nevada. As a result, the laws regarding DUI and operating under the influence of intoxicating substances are also evolving.

Driving high is not a new concept, but it’s becoming the source of more media attention as using marijuana becomes more widespread. Here’s what it means if you’re pulled over for marijuana use and if police officers have the right material.

Traffic Stops and Marijuana DUIs

Driving high is dangerous, just as operating a car under the influence of alcohol is dangerous. Marijuana use delays your reaction time, interferes with your ability to pay attention while on the road, and put you and others on the road at risk of getting into a car accident. Police officers realize this and are subsequently cracking down on marijuana use before driving.

Most DUI arrests result when a driver gets pulled over for a traffic violation. Regarding traffic stops, it’s important to note that a police officer must only have a reasonable suspicion of intoxication. In other words, he or she doesn’t need to see you strictly break any traffic laws.

A police officer may pull you over if you’re weaving around in your lane or even driving very slowly. This alone can serve as evidence of impairment and provide the police with enough suspicion to complete a traffic stop.

A police officer is trained to know when someone is under the influence of marijuana. They may determine you’ve been using by the smell or the presence of mental confusion. Just like with alcohol, you may be required to complete field sobriety tests.

Marijuana is unique in that there is no reliable breath test. If an officer suspects you’re under the influence of the drug, you’ll have to submit to blood testing which will confirm the presence of THC in your system. A high concentration of THC will serve as evidence for a prosecutor to file a DUI charge for impairment.

In San Diego, police officers are now using a mouth-swab device to confirm the driver is under the influence of marijuana. The Drager Drug Test debuted last year and it takes less than 10 minutes for results to come out.

After an officer gives the test and results are positive, they will then take the driver down to a police phlebotomist for a blood test to check precise drug levels. Police say if you smoked marijuana two days before taking the test, there would be nothing to worry about since the machine only tests for active THC compound that is responsible for getting you high.

There are laws in 13 states that prohibit a driver from operating a motor vehicle with any amount THC in their system. An additional five states set a legal cutoff for THC concentration – for Colorado and Washington, its 5 nanograms per milliliters of blood – for Ohio and Nevada, it’s 2.

The rest of the states, including California, prohibit operating a motor vehicle incapacitated by or under the influence of marijuana, which is vaguer and leaves the charges up to the prosecutor.

What About Medical Marijuana?

Some people might assume that the rules exclude medical marijuana use, but this isn’t the case. Operating the under influence is dangerous whether you have a medical marijuana prescription – in fact, there have been some cases where people have been charged with DUI for using other prescription medicines such as Ambien.

Still, this is an evolving area of law. A recent appeals case in Arizona found that people charged with DUI with a medical marijuana prescription may have additional protections from prosecution. In this case, medical marijuana patients in Arizona may be able to contest charges of DUI by providing evidence that they weren’t “too incapacitated” to operate a motor vehicle.

Future DUI Convictions for Marijuana Use

The laws surrounding DUI and marijuana will continue to evolve as use of the substance becomes more widespread. If you live in an area that allows medical marijuana or recreational marijuana use, never use a motor vehicle after smoking.

If you do get behind the wheel of a vehicle after using, you could put yourself at risk of getting a DUI – as well as putting yourself and others on the road at risk. Think of smoking and driving like drinking and driving – find a designated driver or stay at home.