How Do Police Determine Marijuana Impairment?

How Do Police Determine Marijuana Impairment?
Recreational marijuana use became legal in Arizona after the passage of Proposition 207 in November of 2020. However, driving under the influence of marijuana is still illegal, and drivers face harsh penalties if they are convicted of this crime. It's important to understand how police determine marijuana impairment during driving under the influence (DUI) arrests and how this could affect your case.

Signs of Marijuana Impairment

Law enforcement officers may suspect that a driver is under the influence of marijuana based on a variety of signs that may be present before and during a traffic stop. Some of these include:
  • Swerving in and out of lanes, or other driving issues
  • Performance on field sobriety tests (FSTs)
  • Red eyes
  • Smell of marijuana
  • Lack of concentration
There is not one standard set of criteria that an officer must identify to be able to proceed with an arrest and follow-up blood testing. Any number of observations could contribute to their conclusion and as long as there is probable cause, the arrest would be valid. Since probable cause can be subjective, the officer will need to justify their conclusion and this is often a central question in criminal cases.

Does Impairment Matter for Marijuana DUIs in Arizona?

Arizona Revised Statutes (ARS) 28-1381 defines what constitutes DUI. There are three different circumstances that fall under this definition for non-commercial drivers: being "impaired to the slightest degree" by alcohol/drugs, having a blood alcohol content (BAC) of 0.08 or more, or having any drug or its metabolites in one's system. This means that in Arizona, you do not have to be impaired to be convicted of a marijuana DUI. It is unlawful, per ARS 28-1381, to have any marijuana or marijuana metabolites in your system while driving, and this did not change with the passage of Proposition 207. However, police need to have probable cause to make an arrest or conduct a drug test. This means that, although you can be charged with a DUI for marijuana regardless of impairment, whether or not you were showing signs of impairment could impact whether or not the arrest and any subsequent blood tests are valid evidence.

How Long Do Marijuana Metabolites Stay in Your System?

Marijuana is metabolized differently than alcohol and stays in your system for longer. The exact length of time varies based on the frequency of use. For a heavy user, metabolites can be detected in blood for as long as 30 days. Even occasional users can have metabolites in their blood for one to three days. This means that drivers can face serious legal penalties for DUI even if it has been days or even weeks since they actually used marijuana. There have been various cases challenging the use of marijuana metabolites in the blood as evidence for DUI cases. However, based on current laws in Arizona and limited research on how to measure impairment due to marijuana, it is still a factor in DUI cases.

Avoiding Marijuana DUIs

First and foremost, you should never operate a vehicle while under the influence of alcohol or any drug, including marijuana. Most experts estimate that you are impaired for twelve hours after using marijuana, but this varies based on the individual. Driving while impaired is dangerous not only to yourself, but to everyone else on the road. It's not worth the risk. If you are facing marijuana DUI charges, your next step should be contacting an experienced attorney. At DUI Defense Team, we can help you understand the facts that could influence your case and will fight to achieve the best possible outcome.
Contact us today for a free consultation regarding marijuana DUI charges.
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Tucson, AZ. 85716