Michigan should not establish a legal limit for the amount of THC that drivers are allowed to have in their blood, according to a recent report from the Impaired Driving Safety Commission.
THC is the chemical in marijuana that can make people feel high and otherwise affect behavior and mood.
The commission was established by Public Act 350 of 2016 for the purpose of researching and recommending a scientifically supported threshold of THC bodily content to provide evidence for per se impaired driving.
But the commission found that current science shows a poor correlation between blood levels for THC and whether a driver is impaired, and it recommended "against the establishment of a threshold of Delta 9-THC bodily content for determining driving impairment."
The commission said designating a specific level can fail to detect drivers who are impaired and can wrongly flag unimpaired drivers.
Instead the commission recommended the use of roadside sobriety tests to determine whether a driver is impaired.
D.J. Hilson, president of the Prosecuting Attorneys Association of Michigan, said his group hopes the state legislature will follow its recommendations.
The commission's report "really shows that the science in this area is unsettled, that it would be too soon to jump to a presumptive level," said Hilson.
"We're going to focus in on trying the case on the facts of the case, as opposed to worrying about what level somebody was," Hilson said.
Barton Morris, Jr., principal attorney of Cannabis Legal Group, said the commision's recommendations "were very well supported and thought out."
Along with recommending roadside sobriety tests, the commission recommended more training in impaired driver detection for law enforcement officers and prosecutors. It also called for additional research to develop and validate methods that would help in assessing impaired driving under the influence of marijuana.