If Missouri legalizes marijuana, would there be a legal limit to driving like alcohol?

If Missouri votes yes on Amendment 3 to legalize recreational marijuana in November, driving while impaired will still be illegal.

A few readers asked us about how police will enforce this on the road if the drug is legalized.

Reader Tricia Crowder works with families in Jackson County as a court special advocate and said she’s seen firsthand how driving under the influence has impacted families in Missouri.

Crowder asked The Star if recreational marijuana legalization will include a legal limit for how much marijuana a person can consume and still drive, similar to the .08% blood alcohol limit imposed on drinkers.

“How do we kind of draw those healthy limits around recreational use?” Crowder asked. “It becomes a question of: Is the mere presence of marijuana, okay? Or is there going to be a limit to that substance in the body where we say, ‘Hey, this is too much. This is bordering on abuse.”

Local defense lawyers and proponents of Amendment 3 agree that the laws that are already enforced around driving while impaired will not change.

But there are still questions out there about what that would mean in practice.

Here’s a breakdown of what you need to know so far about how legalization might affect laws around driving under the influence.

What is the difference between a DUI and a DWI?

When someone drives after drinking or using marijuana, you will probably hear the term DUI or DWI, which stands for driving under the influence and drinking while impaired. In Missouri, they are technically the same charge and often used interchangeably. You might also hear DUID, which stands for driving under the influence of drugs.

How will law enforcement determine how much weed is in your system?

According to St. Louis-based law firm David Naumann & Associates, Missouri law doesn’t specify a certain level of impairment for DUIDs. When someone is pulled over because they are suspected of driving under the influence of drugs, the police officer will do a set of tests to see if the driver is impaired. The officer can request that a drug recognition expert come to the scene and screen the driver to get an expert opinion.

However, there is no level of exposure that is being tested. People are arrested if they are found to be impaired and unable to drive safely.

So what is considered impaired?

“If you feel different, you drive different,” said Corey Carlisle, a sergeant with the Kansas City Police Department.

The key to determining whether someone is impaired is whether they are able to effectively use all of their senses to operate the vehicle, said Greg Watt, a defense attorney specializing in marijuana charges.

For example, if someone takes a drug that impairs their vision, they will have lost their ability to safely operate a car, even if they feel fairly functional.

“It could be one very acute area of the human condition, or it may be a combination thereof, but being able to safely operate a vehicle takes both physical and cognitive functioning to a certain degree of success in order to properly maneuver that vehicle in a safe manner,” Watt said.

Carlisle agreed that someone who perpetually uses a drug like marijuana is more likely to have the drug show up in a blood test, so he said field tests are one of the best ways to check if that drug is actually impairing the driver.

What happens when you get pulled over?

Before the officer decides to do a field test, they might look to see if the person ran a red light or is swerving, speeding or driving recklessly. They will check to see if the car smells like marijuana or alcohol and then use that information to decide if there should be a sobriety test.

Since officers cannot easily test for weed on the side of the road, the officer typically conducts three tests. To confirm that the person is impaired, that person needs to fail two of the three tests.

The tests include a horizontal gaze nystagmus, where the officer looks to see if the driver’s eye is doing any unnecessary jerking or moving. Then the officer will do a ‘walk and turn’ test, where the officer is looking to see if the person can successfully focus on more than one task at once. For example, a driver might be asked to walk in a straight line and count to 10.

Lastly, the officer will request a one leg stand to see if the person can keep their leg elevated while also counting or answering questions. This is to see if the person can focus on more than one thing at a time, according to Carlisle.

Carlisle added that these three tests are standard practice for police across the country.

“I’ve let plenty of people go who tested but I didn’t have enough signs of impairment to charge them with DUI,” Carlisle said.

There are select police officers in the state who are specially trained as drug recognition experts and are given tools for screening for impairment, according to Watt. There are about eight of these trained officers in KCPD.

These officers are called to the scene if the patrolling officer still can’t make an assessment on if the person is impaired and what kind of drug they have taken.

Once a drug recognition expert arrives at the scene, they will use a separate set of tests including a finger and nose and a modified romberg test. Once the expert makes a decision on what kind of drug the person is impaired by, they will have to take the driver to get further testing to back-up the assessment.

If I get pulled over, can the officer search my car for weed?

Currently, if an officer smells marijuana or suspects that there are drugs in the car, they still reserve the right to search the car. Carlise said although marijuana is decriminalized in Kansas City, most weed is still obtained illegally, so an officer can require a driver to allow for a search and ask for proper documentation for any drugs found.

If recreational weed is legalized in Missouri, the amendment states that marijuana and marijuana infused products should not be seen as “contraband nor subject to seizure.”

There would still be some possession limits and other conditions that law enforcement could use as a reason to search you or your vehicle. If law enforcement doesn’t have evidence that the driver is breaking those possession limits, they should not assume the driver has committed a crime or search their vehicle.

Carlisle added that traffic officers’ main objective is to look for impairment, so the primary objective of the stop is not to search the car but to make sure that the driver is being safe.

What are the potential charges for that?

Driving while under the influence in Missouri is considered a Class B misdemeanor, if it’s the first offense. That first offense can result in up to six months in jail or a $500 fine. Following offenses will result in a Class A misdemeanor and can lead to a year in jail or no more than $2,000 in fines.