Colorado drugged driving prevalence and impaired driving conviction rates

The peer-reviewed journal Traffic Injury Prevention published our manuscript online January 4, 2023.  Colorado drugged driving prevalence and impaired driving conviction rates: Effects of impaired driving definitions and a 5-nanogram limit for delta-9 tetrahydrocannabiniol is based primarily on data published by the Office of Research and Statistics, Division of Criminal Justice in the Department of Public Safety.

The objectives of the study were to answer the following questions:

How prevalent is drugged driving among Colorado drivers convicted of DUI?

What is the conviction rate of drivers charged with DUI?

Is the 5 ng/mL THC permissible inference law effective?

Roughly half of the state’s DUI fillings were attributed to drug use, half to alcohol only.  The largest component of drugged driving was polydrug impairment, led by alcohol combined with marijuana’s THC.  Conviction rates were 91% for alcohol only, 90% for polydrug cases, and 72% for THC only.  Blood drug levels and law structure (per se, permissible inference, DUI definition) affected conviction rates significantly by defendant subsets.  THC only conviction rates in 2020 ranged from 11% to 100%, depending on blood drug levels and the legal charges.


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