Roadside Blood Sobriety Testing: Coming Soon to a City Near You?


As more states legalize marijuana, a breathalyzer alone is no longer enough to allow police officers to detect and detain impaired drivers. As a result, some states are beginning to move toward roadside blood testing kits that can yield instant results for a variety of banned substances. Most people consider the terms “DUI” and “DWI” to be synonymous with driving while drunk. But under Texas law, driving under the influence of any illicit drug (like heroin, MDMA, or cocaine) is just as illegal, as is driving while your motor skills are impaired by your use of a legal prescription medication like Ambien or Xanax.

Advantages of Roadside Blood Testing 

However, alcohol is the only drug that can be detected through a breathalyzer. As a result, even when a driver is visibly impaired, a police officer may not have sufficient probable cause to perform a DUI arrest—at least, not without first transporting the driver to a nearby hospital for more thorough testing.

Police vans that are equipped with blood testing equipment are changing this, however. If a driver refuses to submit to a blood draw, the responding officer can quickly fill out and electronically submit a search warrant, which is immediately transmitted to a judge for review. Once the warrant has been approved (often in a matter of minutes), the officer has full permission to perform a blood test of the driver, and the driver’s refusal will result in arrest.

Using these special DUI vans, which have a table, refrigerator, and a medical supply cabinet inside, officers who have been trained in phlebotomy can quickly secure a blood sample and run an array of tests on it. These tests can reveal the presence of “active” marijuana (as opposed to the metabolites that remain in one’s system for days after use), as well as cocaine, opioids, amphetamines, and prescription painkillers and sedatives.

Proponents of these mobile DUI vans claim that they provide much quicker and more accurate results than hospital blood tests. Because so many illicit drugs are metabolized quickly, a delay of a few hours or more between a traffic stop and a blood test can be enough for the drug to clear the system. By performing this test within an hour (or sometimes even within 15 minutes) of the stop, officers are provided with a clearer picture of the driver’s impairment.

Potential Defenses to a Positive Roadside Blood Test

Although these roadside blood tests aren’t being implemented in Texas yet, the state’s consistently high DUI statistics (along with neighboring states’ use of DUI vans) means it’s likely to join this effort soon.

But the DUI vans aren’t without their critics, who point to an increased risk of injury or infection from mobile blood testing. Unlike the noninvasive breathalyzer test, critics argue, blood draws puncture the skin and may violate an individual’s constitutional rights. It’s likely that any challenges to this practice will be made on a case-by-case basis, but those arrested for DUI after a positive blood draw may be able to attack not only the circumstances of their individual arrest but the entire process itself.