I think I've heard that they have been coming up with more reliable testing methods as more and more states decriminalize/legalize MJ, and I suspect that the technology will continue to be developed.
1. What is DUI of marijuana in Colorado?
You drive under the influence (DUI) of marijuana in Colorado when as a result of consuming marijuana you are substantially incapable, mentally and/or physically, to safely operate a vehicle. Under 42-4-1301, C.R.S., DUI of marijuana is usually a misdemeanor.
Unlike alcohol, there is no DUI “per se” of marijuana. DUI of drugs must be proved by objective evidence that you were unable to drive safely. However, it is a permissible inference that you drove under the influence of marijuana if your blood contained 5 nanograms or more of delta 9-tetrahydrocannabinol (THC) per milliliter.1 THC is the active ingredient in most strains of marijuana.2
But even this amount of THC in the blood is not conclusive. The best Colorado DUI lawyers can challenge it in court. To prove you guilty of DUI of marijuana, the prosecutor will need to show that you were actually too stoned to drive safely. Such evidence might include:
You violated Colorado traffic laws,
You were weaving in and out of your lane,
You drove too fast or too slow,
You appeared stoned (bloodshot eyes, slurred speech),
The officer smelled marijuana in the car,
There was marijuana paraphernalia in the vehicle (e.g., rolling papers, a bong, a joint clip, etc.), or
Marijuana was found in your car.
4. Do I have to take a DUI blood test?
By driving in Colorado, you give your “express consent” to take a chemical test if you are lawfully arrested for DUI or DWAI.6 This does not refer to the roadside preliminary breath test an officer may ask you to take after a traffic stop.7 Unless and until you have actually been arrested, you are not obligated to take a chemical test.
If you are actually arrested, however, refusing a Colorado DUI chemical test has serious consequences. If alcohol use is suspected, you will be offered your choice of a DUI breath test or DUI blood test. If, however, the officer reasonably believes you were using drugs, you may be required to take a blood test instead of -- or in addition to -- a breath test.
.