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A north Texas university developed a THC detection test for drivers. Is it effective?

A north Texas university developed a THC detection test for drivers. Is it effective?

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Driving under the influence of marijuana can be a serious crime in Texas, just like driving under the influence of alcohol.

However, marijuana is not as easily detectable as alcohol, where officers can administer a breathalyzer to measure a driver’s BAC level. Researchers at the University of Texas at Dallas are working to give police officers a new THC detection tool that they say is 95 percent as accurate as blood tests.

The test involves a sensor that measures THC in the test subject’s saliva. THC is the psychoactive component in marijuana that causes the “high” feeling. THC affects the user’s memory, decision making, coordination and other vital functions needed to drive safely.

THC breaks down into molecules called metabolites, according to the university. Researchers measure the electrochemical activity of the metabolites, or how they react to the electric field. The UT Dallas test focuses on the electrochemical signal of one metabolite and measures how strong the THC concentration is inside of the metabolite.

Put simply, the researchers measure THC from saliva collected in a cotton swab.

But like other THC tests officers use, the saliva test is not without its flaws. Researchers say there are more interfering molecules in saliva, which can make it difficult to get an accurate THC reading. Saliva can be acidic too, which can mask certain electrochemical signals.

Driving under the influence of drugs in Texas

Still, Texas law enforcement can have issues proving intoxication by marijuana, drugs, illegal substances or prescribed medications. Unlike DWI cases involving alcohol, there is little scientific support for a quantifiable number or percentage of THC to prove a person is impaired. Marijuana can also be detectable in a person weeks after they ingested it but may not impair their ability to drive at the time her or she is tested for it. Researchers at UT Dallas did not say if their test only detects recently consumed marijuana or THC that was consumed days or weeks ago.

Despite the questionable testing, driving under the influence of drugs is a serious crime in Texas. State law does not distinguish between an individual under the influence of drugs or under the influence of alcohol. A driver in Texas is considered intoxicated if he or she no longer has normal control over his or her mental faculties.

Officers may use field sobriety tests, blood tests or urine tests to determine if an individual is under the influence of marijuana or other controlled substances. Any amount of an illicit substance found in blood or urine can be used as evidence, even if the driver took the substance days before and isn’t impaired by it at the time he or she was pulled over.  

Punishment for conviction of driving under the influence of drugs in Travis County

Refusing a test for driving while intoxicated by drugs can result in having your driver’s license suspended for 180 days. A second test refusal within a 10-year period can lead to having a license suspended for up to two years.

Driving While Intoxicated are Class B misdemeanor charges that are punishable by up to 180 days in jail with fines up to $2,000. The driver can lose their driving privileges for up to a year and have an additional mandatory fine up to $6,000 per year.

Fines and penalties for DWI/DUIs increase for each one an individual gets. By a third conviction, the driver can be sentenced to 10 years in prison, loss of driving privileges for up to two years, and pay fines up to $10,000.

Given the discrepancies in marijuana testing and the ability to show positive results weeks after ingesting the substance, it is within the accused’s interest to retain legal representation when facing a DWI/DUI in Travis County.

About The Author
Kevin Bennett
As a native Texan, Kevin Bennett knows that his state has a reputation for being tough on crime. This can lead to an overwhelming feeling of stress when facing charges in Texas. The criminal justice system is daunting and confusing. Kevin Bennett is determined to guide his clients through it with as little stress as possible by maintaining open communication while aggressively fighting the charges ...read more


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