Colo.'s Marijuana DUI Law Opens Door to Defense

By Betty Wang, JD on June 13, 2013 | Last updated on March 21, 2019

Marijuana DUI laws differ by state, and Colorado is no exception. But now that recreational marijuana use is legal there (for most adults, anyway), how are officers supposed to approach drivers suspected of driving while high?

A new law that sets a legal limit for driving under the influence of marijuana is now in effect in Colorado. Much like how there is a legal limit for blood alcohol levels, there is now one for THC -- the psychoactive ingredient in marijuana -- of 5 nanograms per milliliter of blood.

While a 5 ng/mL limit for THC is not unheard of (Washington state, which also legalized recreational pot last fall, enforces the same limit), Colorado's law is different, The New York Times reports: It allows defendants to introduce evidence that pot did not impair their ability to drive.

Proving Pot Had No Effect

An ongoing question in states considering relaxed marijuana laws centers on the effects of being high versus being drunk, especially behind the wheel.

Many pot users claim that they are not measurably impaired while under the influence of marijuana, and that pot doesn't affect their driving as much as a few drinks would. Colorado's marijuana DUI law attempts to recognize that, and gives defendants an opportunity to prove it.

However, it's not entirely clear how a drugged-driving defendant would try to prove his driving abilities were not affected by the use of marijuana. One potential route would be for an experienced DUI lawyer to have his client take part in a videotaped driving test while high, like tests conducted by Seattle's KIRO-TV, and play the results in court.

Other Potential Defenses

Until more marijuana DUI cases are argued in court, however, lawyers may have to try a number of different defense strategies to figure out which ones are most effective.

Some other potential defenses may include:

  • Faulty tests. Breathalyzer, urine, and blood tests can produce faulty results, which a defendant can challenge. For example, lab equipment used for blood tests must be routinely and carefully calibrated, and can also be susceptible to human error. Issues with a blood sample's chain of custody can also raise questions about test results.
  • THC takes longer to be metabolized. Unlike alcohol, which typically dissipates from your system in a matter of hours, THC can linger for days or even weeks, depending on how much marijuana the user smokes. A chronic pot smoker could potentially try to use this fact in his defense.

For those of you excitedly packing your bong for a trip to the Centennial State, slow down a bit. While the effects of marijuana and alcohol can lead to different results physically (and now legally), both substances can significantly impair your skills when driving. DUIs still have dire consequences, and driving while high can still steer you toward a conviction.

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