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Understanding DUI-D in Colorado: The Role of Polydrug Use

In Colorado, where approximately 25,000 DUI cases are reported annually, concerns about drugged driving have been a topic of debate, particularly in the context of marijuana legalization. While some opponents of marijuana legalization argue that it leads to an increase in drugged driving incidents, the relationship between marijuana legalization and DUI-D cases remains a complex and evolving issue. Recent research sheds light on the factors contributing to DUI-D and challenges commonly held beliefs about the primary causes of these cases.

Contrary to the notion that marijuana alone is the predominant cause of drugged driving in Colorado, a study published in the Journal of Safety Research suggests that polydrug use, the simultaneous consumption of multiple substances, is a more prevalent factor in DUI-D cases. This study’s findings have significant implications for DUI-D enforcement and testing methods.

Polydrug Use: A Leading Contributor to DUI-D

According to the study, the most common cause of DUI-D cases in Colorado is not marijuana, alcohol, or prescription medication on its own but rather a combination of drugs. Polydrug use was identified as the primary factor in 18.8 percent of the cases studied. In contrast, 70 percent of cases involved alcohol as the sole substance involved, while only 11.2 percent were attributed solely to drugs.

These results highlight the significance of polydrug use in the context of DUI-D, where individuals often consume a combination of substances, such as alcohol and marijuana, leading to impaired driving. While alcohol remains the leading contributor to DUI cases, the study emphasizes that polydrug use plays a crucial role in DUI-D incidents.

Implications for DUI-D Enforcement and Testing

The study’s findings suggest a need for more comprehensive and effective methods of testing for drugs after DUI-D incidents occur. Currently, Colorado has established a legal limit of 0.05 nanograms of THC (the psychoactive component in marijuana) in the blood as the threshold for determining impairment. However, this benchmark has its limitations.

The study underscores the complexity of assessing impairment based solely on THC levels in the blood. Unlike alcohol, where a specific blood alcohol concentration (BAC) threshold indicates impairment, THC affects individuals differently, making it challenging to establish a universally applicable THC threshold for impairment. For frequent marijuana users, THC may remain detectable in the bloodstream for an extended period, even when they are not impaired.


In conclusion, while the debate surrounding the impact of marijuana legalization on DUI-D rates continues, recent research suggests that polydrug use is a significant factor in DUI-D cases. This underscores the need for more sophisticated testing methods and a nuanced approach to evaluating impairment caused by the combination of substances. For individuals facing DUI-D charges and related legal issues in Colorado, seeking legal counsel, such as the services provided by Thomas & Ahnell, LLC, a law firm specializing in alcohol and drug-related driving offenses, can be crucial in navigating the complex legal landscape.

Do you have further questions or concerns? Call us or contact the attorneys at Thomas & Ahnell, LLC, and we will be happy to help.

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