The Massachusetts Supreme Judicial Court has just ruled that some police testimony about field sobriety tests is inadmissible in cases involving suspected marijuana impairment. This is because there is no scientific certainty that the field sobriety tests used on drunk drivers yield useful information when used on drivers suspected of marijuana impairment.
The high court was careful to say that there is significant research, if not agreement among researchers, that using marijuana does cause driving impairment. However, the unanimous court ruled that there is insufficient evidence that field sobriety tests accurately measure marijuana impairment.
Whenever there is no clear scientific consensus on the reliability of evidence, that evidence can be admitted but the witness (the police officer) presenting it cannot claim to be an expert. Legally, that means the officer cannot lawfully offer an opinion about the outcome and meaning of the test. Officers will only be allowed to describe what they saw when performing the tests.
In other words, police witnesses will be allowed to:
- Offer their observations about how a driver suspected of marijuana impairment performed on field sobriety tests
They will not be allowed to:
- Say whether the defendant passed or failed the tests
- Provide opinions about whether the defendant was too high to drive
- Treat poor performance on a field sobriety test as conclusive proof that the defendant was impaired
The challenge to the use of field sobriety tests in marijuana impairment cases was brought by a man who was pulled over in Millbury on suspicion of impaired driving. The state trooper found evidence of marijuana smoking going on in the car, which was occupied by the driver and two passengers. The passengers said they had smoked as recently as 20 minutes beforehand, but the driver said he had not smoked for three hours.
When the trooper administered field sobriety tests, the driver was unable to follow the instructions for a test called the “walk and turn.” The trooper concluded the driver was impaired — but the high court now says he had no scientific basis for that conclusion. There is currently no scientifically valid test to determine marijuana impairment.
This ruling only applies here in Massachusetts, but it could be influential in any state where the use of marijuana is legal for some purposes but not while driving. Our state legislature has ordered a special commission to be created which will study issues surrounding marijuana intoxication and driving.