The Intersection of Marijuana Use and Impairment Testing

Marijuana legalization is on the rise. With that, employers and the law are struggling to find ways to ensure that the drug does not hurt anyone in the workplace. Although it is still illegal under federal law, marijuana use is becoming widespread across the United States. As a result, employers and law enforcement agencies are stepping up efforts to test for marijuana impairment. In this article, we will delve into the various types of Marijuana impairment test and what they entail.

Standard Field Sobriety Tests (SFSTs)

SFSTs are the most common of the marijuana impairment tests. Originally developed to test the driving ability of alcohol-impaired drivers, SFSTs can also indicate whether a driver is impaired by marijuana. The tests involve three different assessments, namely the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test.

The horizontal gaze nystagmus test is designed to measure the suspect’s eye response to peripheral stimulation. The walk and turn test is designed to test the suspect’s processing and attention abilities and the one-leg stand test is a balance test.

Drug Recognition Expert (DRE) Evaluation

A DRE is a specially trained officer who can assist in determining if the driver is under the influence of marijuana. A DRE can be called in if an officer is unsure of the driver’s impairment level or if an SFST has been administered but some impairment is still suspected.

During a DRE evaluation, the officer assesses the driver for a variety of physical signs and symptoms, including heartbeat, blood pressure, body temperature, pupil size, eye movements, and muscle tone. The DRE then looks at factors like the driver’s behavior and statements to determine if the driver is impaired.

Cannabis Quantification

This is a new impairment test that attempts to quantify marijuana impairment. Cannabis quantification involves testing the driver’s blood, urine, or saliva for the presence of THC, which is the psychoactive component of marijuana. Although this test can identify marijuana impairment, it has several limitations, such as the fact that THC can remain detectable in the system for days after use and that the results do not reflect the level of the driver’s impairment.

Field Enzyme-Linked Immunosorbent Assay (ELISA) Tests

Field ELISA tests function in a similar way to cannabis quantification, by testing for the presence of THC. These tests are taken on-site, and the results can be read within minutes. Like others, these tests can give false positives, making it important for police officers to use their discretion in assessing the suspect’s impairment.


Marijuana impairment tests come in a variety of forms. The standard field sobriety tests (SFSTs) are the most commonly used. They involve the horizontal gaze nystagmus test, the walk and turn test, and the one-leg stand test. There are also drug recognition expert (DRE) evaluations, which provide further evidence of a suspect’s impairment. Cannabis quantification and field enzyme-linked immunosorbent assay tests are also gaining traction. Employers, law enforcement agencies, and employees must work together to find ways to ensure public safety while also respecting people’s rights to use marijuana for medical or recreational purposes. This involves, among other measures, extensive testing and continuous improvement of testing technology to ensure reliable and consistent results.