A prosecutor blamed the Beer crash on “speed and weed,” but a jury that heard expert testimony on marijuana’s effects at his trial deadlocked on a homicide charge and other felonies related to whether the teenager was impaired by marijuana.
Studies of marijuana’s effects show that the drug can slow decision-making, decrease peripheral vision and impede multitasking, all of which are important driving skills.
[...] combining marijuana with alcohol appears to eliminate the pot smoker’s exaggerated caution and to increase driving impairment beyond the effects of either substance alone.
Dr. Mehmet Sofuoglu, a Yale University Medical School expert on drug abuse who testified at Beer’s trial, said studies of marijuana and crash risk are “highly inconclusive.”
“Being a teenager, a male teenager, and being involved in reckless behavior could explain both at the same time — not necessarily marijuana causing getting into accidents, but a general reckless behavior leading to both conditions at the same time,” Sofuoglu told jurors.
Columbia University researchers compared drivers who tested positive for marijuana in the roadside survey with state drug and alcohol tests of drivers killed in crashes.
When adjusted for alcohol and driver demographics, the study found that otherwise sober drivers who tested positive for marijuana were slightly less likely to have been involved in a crash than drivers who tested negative for all drugs.
“If states legalize marijuana, they must set clear limits for impairment behind the wheel and require mandatory drug testing following a crash,” said Deborah Hersman, former chairwoman of the National Transportation Safety Board.