Stoned DUI: How Does a Marijuana Drug Test Work?

How do cannabis drug tests work

Public opinion of marijuana has changed drastically over the years. As the years roll by, fewer people are harboring the belief that cannabis is extremely dangerous to a person’s health. In fact, a lot of people are opening up to the idea of cannabis being a socially acceptable drug. That being said, there is still a considerable number of folks who are raising concerns about other problems that are related to marijuana use. For example, people are still not convinced that driving after using marijuana is completely safe. According to their belief, the use of cannabis impairs a person’s ability to drive responsibly and safely.

Since there are people who aren’t willing to hand over the steering wheel to stoners, the authorities and lawmakers have come up with new ways of detecting marijuana use among drivers.

In simpler words, the police have devised a drug test for stoned DUI.

The state of California has specific rules and regulations in place to prevent people from driving under the influence of marijuana. Anyone who smokes weed and resides or commutes to California should be aware of how a drug test is conducted by the police. This is because failure in the test could give the law enforcers a probable cause to arrest you and hold you in custody.

The Field Sobriety Test

This is one of the most common tests for detecting DUI. If you are pulled over by a California officer who has good reason to believe that you are stoned, then the officer holds the right to verify his or her suspicions by carrying out a field sobriety test.

For those of you who are not aware of what a field sobriety test is, it is essentially a series of physical and mental exercises that suspects are asked to perform by the police during marijuana DUI investigations.

The performance of the suspect during the exercises will help the police determine the person’s degree of impairment. In the state of California, law enforcers are heavily dependent on field sobriety tests because they believe that it is the most reliable way of figuring out whether a person is too impaired to be behind the wheel.

traffic stopThe sobriety tests carried out by the officials aren’t always the same. There are three standardized tests that are usually conducted. The onus is on the official to decide whether more than one standardized test is required to confirm the suspicion of DUI. The following are some important details regarding the three standardized tests that you could expect to be taking if you are pulled over while stoned:

Horizontal Gaze Nystagmus Test

You have probably seen this on an episode of Cops before. This simple test is administered by a law enforcement official by moving an object sideways in front of the suspect’s face. In certain cases, the moving object is the officer’s finger. The reason why this is done is because the movement of any object that is placed right in front of the eyes can cause an involuntary reaction in a person who has been driving under the influence of alcohol or drugs. The involuntary jerking of the eye has been medically proven to be related to high levels of intoxication.

It is completely normal for a person’s eye to jerk after it has been strained beyond an angle of 45 degrees. However, if the jerking occurs well below the 45 degree mark, then the California state police official has the legal authority to reference this involuntary action as evidence against the suspect. According to The National Highway Traffic and Safety Administration, these tests turn out to be correct around 80% of the time.

Walk and Turn Test

The walk and turn test is designed to divide the suspect’s attention between physical and mental exercises. It is basically a test of one’s coordination. This test is commonly referred to as the walk line test. After instructing the suspect, the officer checks for the following:


a) Loss of balance

b) Breaks in walking

c) Inability to remain on the line

d) Inability to follow instructions (starts walking before being told to do so or walks the wrong number of steps)

The NHTSA has confirmed that this test has a 68% success rate.

One Leg Stand Test

As the name suggests, the one leg stand test requires the suspect to raise his or her foot, remain still in a fixed posture, count to a certain number and look down at the ground. If the suspect struggles to follow the above instructions and begins to sway, hop or put their foot down, then the office can take further legal action against the person. This test is slightly less accurate than the walk and turn test.

Touch noseOther Tests for Marijuana DUI

Besides the three standardized sobriety tests, there are other ways in which law enforcers can confirm whether a person has been driving under the influence or not. In California, a person who has been pulled over in suspicion of driving under the influence of cannabis has already given their consent to a blood, urine or breath test. The urine test is usually used as a last resort by the officials. Another test known as the saliva drug swab test is administered at DUI checkpoints to detect marijuana, cocaine, meth and other drugs in a driver’s system. This eight minute long test has drawn a lot of controversy as people are not convinced that this is the most accurate way of detecting marijuana use.

Problems with Standardized Tests for Marijuana DUI

Stoned DUI is a much more complicated issue than drunk driving. First of all, it is very difficult to figure out whether the suspect had used marijuana moments before getting in the car or several hours before driving. On top of that, the drug kits used by the police are very cheap, highly inefficient and absurdly inaccurate.

Furthermore, many police officials are not educated on how drug kits work.

Because of all these problems, numerous innocent users of marijuana have been falsely convicted and sent to jail for a crime they never committed.

Stoned DUI: How Does a Marijuana Drug Test Work? was last modified: by
Grace O'Brien
About Grace O'Brien
Grace writes blogs and strain articles for Wikileaf. After completing her Masters, she focused solely on writing and thus gained a lot of experience. She lives in London with her daughter and two pet dogs.