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How does law enforcement prove driving under the influence of marijuana?

On Behalf of | Apr 15, 2022 | Firm News |

Drivers face a relatively straightforward set of protocols when tested for alcohol impairment. The officer will pull over the driver and get an initial impression of whether the driver consumed alcohol. While protocols vary, the officer may then have the driver do field tests to determine intoxication. The officer then may use a breathalyzer and/or bring the driver in for a blood test to determine if the blood alcohol content passes the .08 threshold. The courts regard the breathalyzer readings as accurate, and untainted blood samples are indisputable evidence.

Marijuana impairment is harder to determine

Colorado is obviously a state where it is legal to buy and consume marijuana, but there are still laws prohibiting impaired driving while under the influence of marijuana. However, it is much more complicated trying to determine the driver’s intoxication level because there is no .08 BAC intoxication threshold.

A general rule is that five nanograms of THC or more in the bloodstream is intoxication, but this is not grounds for arrest. Moreover, different drivers have different tolerance levels to the drug. Instead, the officer must look for signs of intoxication. This may involve reckless or erratic driving, the smell of marijuana in the vehicle or on the person, bloodshot eyes or dilated pupils, behavior that implies intoxication, or other signs.

DRE protocols are also employed

Colorado employs a Drug Recognition Experts (DRE) program that trains law enforcement to recognize impairment in drivers. The program involves many areas of law enforcement in the state with support from the National Highway Traffic Safety Administration. DRE is a standardized method for examining drivers. The methodology determines:

  1. Impairment
  2. Whether the impairment the result of drugs, alcohol or a medical condition
  3. What category or categories of drugs caused impairment

Several different examinations can be conducted, including breathalyzer, physical examination, psychological tests, information gathering during interviews, and toxicological examinations.

Many of these signs are subjective

It is a fact that THC remains in the bloodstream for days after the intoxicating effects end, so law enforcement must rely on training and experience to draw its conclusions. Because the signs can be subjective, drivers should defend their rights regardless of the officer’s beliefs and the charges filed. The courts will still need valid evidence to convict the driver.