Court rules cops can use field-sobriety tests meant for drunk drivers on possibly stoned drivers, but with a caveat

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.

The absence of scientific consensus regarding the use of standard FSTs in attempting to evaluate marijuana intoxication does not mean that they have no probative value. A police officer makes numerous relevant observations in the course of an encounter with a possibly impaired driver. There is no doubt that an officer may testify to his or her observations of, for example, any erratic driving or moving violations that led to the initial stop; the driver's appearance and demeanor; the odor of fresh or burnt marijuana; and the driver's behavior on exiting the vehicle.

In our view, certain of the FSTs also may provide information that is relevant to the question of a defendant's impairment, and a police officer may testify, as a lay witness, to his or her observations of the defendant's performance. In particular, observations of the performance of the OLS and the WAT may be admissible as evidence of a defendant's balance, coordination, ability to retain and follow directions, and ability to perform tasks requiring divided attention, and the presence or absence of other skills necessary for the safe operation of a motor vehicle. We see no reason why an officer's observations of a defendant's behavior on being asked to walk a straight line or to stand on one foot should be excluded because the scientific community's understanding of precisely how this correlates with marijuana use is still evolving. We are not persuaded, however, that the FSTs can be treated as scientific tests establishing impairment as a result of marijuana consumption. The scientific community has not reached a consensus as to whether a defendant's performance on any combination of FSTs, or on any individual FST, is correlated with marijuana use or impairment. The unsettled state of the scientific research suggests that FST evidence neither should be treated as a definitive test of impairment nor excluded entirely from consideration by the finder of fact.