The Supreme Judicial Court ruled today that while current field-sobriety tests were developed to gauge whether somebody is too drunk to drive, they can provide valuable information if the driver is suspected of being stoned, instead.

But, the court cautions, police and prosecutors will have to use more than just field-sobriety tests as an argument to a jury or judge that a person was operating under the influence of marijuana - because scientists are still debating the best way to prove that an impaired driver was, in fact, impaired by pot consumption.

The ruling comes in the case of a guy charged with operating under the influence of marijuana in Milbury, after a state trooper stopped him because his rear lights weren't on and then noticed a haze and the distinct smell of smoked pot inside.

Although the man was able to recite numbers backwards and follow a moving object, he had problems with tests involving walking heel to toe and standing on one foot:

Rather than standing heel to toe, with his right foot in front and his left toes touching his heel, as he had been shown, Gerhardt moved his feet so that they were side by side; he also did not turn around as instructed. French determined that "the results of this test indicated that Gerhardt was impaired." The trooper then provided instructions and gave a demonstration of the [stand on one leg] test, and Gerhard indicated that he understood. In performing the test, however, Gerhard did not remain upright on one foot, instead putting his foot down multiple times, and swayed.

The court said that field-sobriety tests remain useful in helping a police officer determine whether a driver is too impaired to drive - but by themselves are not enough proof of being impaired by marijuana.