Texas Drug Test. There are many illegal, prescription, and over-the-counter drugs that can impair people when they take to the roads. Drivers under the influence of drugs can potentially experience negative impacts to their coordination, reaction times, perception and judgment, and overall attention. The impairing effects of drugs can vary in individuals; aside from people having different levels of drug tolerance, many drivers who get arrested for driving under the influence (DUI) have used more than one drug type or a combination of drugs and alcohol which can result in different effects. 


The National Highway Traffic Safety Administration (NHTSA) has been reviewing the impacts of drug use on driving in recent years, focusing on things such as duration of effects from drug use, drug interactions (with other drugs and/or alcohol), and effects on skills required for driving, such as lane tracking and response times for breaking to stop. Though the NHTSA has studied a wide range of drugs, one of the main drugs researched is cannabis, or marijuana. 

Drugs and Driving

NHTSA has conducted research studies that determined marijuana has impacts on driving skills, both alone and in combination with alcohol, and that many drivers on the road have marijuana in their system while on the road. The most recent 2013-2014 National Roadside Survey (NRS) conducted by the NHTSA reported that approximately 22% of drivers had used a potentially impairing drug–including marijuana–during the workweek and on weekend nights, with percentages between 12% and 15% specifically having used those drugs illegally. However, NHTSA has also determined in their report, Marijuana Impaired Driving: A Report to Congress, that levels of THC (the mind-altering chemical in marijuana) in a driver’s blood or urine should not be used as indicators of impairment.  The report goes on to say that the scientists that analyze a driver’s blood or urine sample are not able to testify that a specific level of THC means that a driver is impaired by marijuana or unable to drive safely.


As marijuana has become more readily available in the US, the number of people driving under the influence has also increased. While law enforcement officers currently have the option of administering blood or breath tests to determine if someone is impaired from having too much alcohol to drink, there is no effective test for drugs like marijuana.  Officers rely mainly on field sobriety tests (SFST) for attempting to determine if a driver is intoxicated, but there is a fundamental flaw in using those because SFSTs were designed for detecting signs of intoxication for someone under the influence of alcohol.  Additionally, an officer administering one of the three field sobriety tests, the Horizontal Gaze Nystagmus (HGN) or light in the eye test should not observe any clues of intoxication at all for someone who has only been using marijuana.  Law enforcement will also call in an officer with some additional training as a Drug Recognition Evaluator to administer additional tests and make observations. There are problems with the tests that Drug Recognition Evaluator (some like to call themselves Drug Recognition Experts).  Different testing methods are being researched as the Drug Recognition Evaluator/Expert program for law enforcement officers has come under fire more and more due to its role in sending innocent people to jail.


Part two of this blog series is a deeper discussion of the research and development of roadside drug tests for use during traffic stops.

Texas Drug Testing Laws

Texas Drug Test. If you or a loved one is charged with a cannabis-related crime in Texas but are unaware of the law and how it applies in your case, consider seeking legal assistance from an attorney with an in-depth understanding of marijuana laws, the science and techniques used to analyze blood or other substances seized during an arrest, and experience in such cases. Reach out for legal advice from the counsel at the Collin Evans Law if you need help fighting charges for a marijuana DWI offense in Houston, Texas or the surrounding area. You can contact Collin Evans online or by calling 713-225-0650.