As more states make medical and recreational marijuana use legal, they increasingly are grappling with what constitutes driving under the influence of drugs (DUID) and how to detect and prosecute it. They're finding it is more difficult than identifying and convicting drunken drivers, reports Stateline. While marijuana is found more often than alcohol in drivers involved in car accidents, the rate at which it actually causes crashes is unclear. At least 17 states have “per se” laws making it illegal to have certain levels of THC (the main marijuana ingredient) in one's body while operating a vehicle, says the National Conference of State Legislatures (NCSL). Under these laws, no additional evidence is required to prove a driver is impaired.
Of those states, Colorado, Montana, Nevada, Ohio, Pennsylvania and Washington allow for some amount of THC to be found in a driver's blood, ranging from 1 to 5 nanograms per milliliter. Other states leave no wiggle room and consider any amount of THC to be impairing and grounds for being charged with DUID. Alaska, Colorado, the District of Columbia, Oregon and Washington allow adult recreational use of marijuana, and another 18 states permit its use for medical purposes. More states are expected to permit recreational marijuana use as legalization efforts move to the ballot in Ohio this fall and Nevada in 2016. At a recent NCSL meeting in Seattle, policymakers at a session on legalizing marijuana said they expected their states would soon have to debate legalization, if they haven't already. The Pew Research Center said in April that 53 percent of adults supported the legal use of marijuana.