With efforts underway for marijuana legalization in North Carolina lining up with successful initiatives across the country, traffic safety officials are turning their thoughts to concerns about drug-impaired driving. Police and prosecutors are able to measure blood alcohol concentration, and 0.08 percent is the legal limit for alcohol intoxication across the country. However, no similar situation exists for cannabis; there is little scientific consensus about the level of cannabis intake that affects a person’s driving ability. In addition, there are no generally accepted roadside screening devices that allow police to assess impairment at an accident scene or traffic stop.

The National Transportation Safety Board called on the National Highway Traffic Safety Administration to work to formalize standards for both drug impairment and assessment devices. The recommendations were prompted by a 2017 crash that killed 13 people. After the accident, the driver responsible was found to have sedatives and cannabis in his bloodstream.

Opiate-related impairment has also drawn official attention. As the opioid crisis spreads across the country, evidence has indicated that more accidents have involved driving under the influence of drugs. In 2006, tests of drivers who died in car crashes indicated that 30 percent tested positive for drugs. By 2015, that number had risen to 46 percent, indicating an upward trend. One set of random roadside tests indicated that 22 percent of drivers showed evidence they had been using drugs.

However, evidence of drugs in a person’s system is not evidence that they were related to the crash. People can face prosecution for even minimal amounts of drugs detected in a blood test. When people are arrested and accused of driving under the influence, a criminal defense lawyer may be able to help them fight back against the charges. An attorney might challenge police and prosecution evidence and work to avoid a conviction.