Marijuana use is now legal in California, but is still illegal to drive while under the influence of marijuana. So, how do police determine that you are “under the influence” of marijuana?

Let’s explore how police determine impairment in DUI marijuana cases.

No BAC Test for Marijuana

In DUI cases involving alcohol, police will likely administer a breath test. If your blood-alcohol content level is 0.08% or higher, you are considered to be under the influence of alcohol. However, no such test exists for marijuana at the moment.

The reason why marijuana is much more difficult to test for is because THC, the active compound in marijuana that causes impairment, is processed by your body in a much different way than alcohol. Traces of THC can be found in your bloodstream hours and days after consuming it, long after the effects have worn off.

States such as Colorado and Washington have set the legal limit for marijuana at 5 nanograms per milliliter of blood, but there is no clear scientific consensus to what the limit should be nor are there effective tools for measuring THC levels.

Field Sobriety Tests for Marijuana

Importantly, some people may be taking marijuana to counter medical conditions that cause imbalance or lack of coordination. Therefore, field sobriety tests are not reliable when it comes to determining whether someone is impaired by marijuana.

Field sobriety tests were specifically designed to determine whether someone is under the influence of alcohol. If police used field sobriety tests to determine you were driving under the influence of marijuana, your DUI defense lawyer may be able to attack the DUI charge by showing they are not effective in marijuana cases.

Drug Recognition Experts

Without a legal THC limit to guide prosecution in cases involving driving under the influence of marijuana, law enforcement and prosecutors have turned to outside experts to help build their cases.

“Drug recognition experts” (or DREs) assess the behavior of drivers over a period of one hour, measuring data such as the driver’s pulse, blood pressure, eye exams, balance tests and/or other indicators that may show the driver was driving under the influence of marijuana.

Prosecutors may use the testimony of DREs to analyze evidence from the alleged marijuana DUI. However, not all of these “experts” are medically trained, and a judge is not required to allow testimony from a DRE.

If you or someone you love has been accused of driving under the influence of marijuana, you should speak to an experienced DUI lawyer who can attack the evidence against you and provide a strong defense.

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