Can A Field Sobriety Test Show If A Driver Is Too High To Be Behind The Wheel? Massachusetts Court Says "No"

Posted by Richard Lawson | Sep 29, 2017 | 0 Comments

Field sobriety tests (FSTs) are one of the common ways for law enforcement officers to determine if a driver is too intoxicated to be behind the wheel. While these tests may be useful in figuring out if a driver has been drinking alcohol, their effectiveness in determining if a driver is under the influence of another substance is not as certain. Recently, the Massachusetts Supreme Judicial Court, in the case of Commonwealth v. Gerhardt, looked at a number of issues concerning field sobriety tests and reached the following conclusions:

  • “Police officers may not testify to the administration and results of FSTs as they do in operating under the influence of alcohol prosecutions. Police officers may testify to the administration of 'roadside assessments' in the manner set forth in this opinion."
  • "A lay witness may not offer an opinion that another person is 'high' on marijuana."
  • "A police officer may testify to observed physical characteristics of the driver such as bloodshot eyes, drowsiness, and lack of coordination. The officer is not permitted to offer an opinion that these characteristics mean that the driver is under the influence of marijuana."
  • "Jurors are permitted to utilize their common sense in assessing trial evidence.”

Facts of the Case

The case dealt with a driver, Gerhardt, who had been pulled over after a police officer noticed the vehicle didn't have its rear lights on. When the officer approached the vehicle he saw smoke, smelled marijuana, and Gerhardt admitted there was pot in the car. However, he stated that he had not smoked for several hours. The officer asked Gerhardt to step out of the vehicle and perform a number of FSTs, including the walk and turn test, the horizontal gaze nystagmus test, the one leg stand test, reciting a portion of the alphabet, and counting backward between a certain set of numbers. While Gerhardt passed the latter two tests and had no nystagmus indicators, he did not perform the walk and turn test or the one leg stand test correctly. Based on the FSTs, the officer arrested the driver and he was later charged with DUI-Marijuana.

Gerhardt filed a motion contesting “the admissibility of evidence concerning his performance on FSTs conducted after the [traffic] stop.” The District Court held a hearing on the matter and later Gerhardt asked the state's high court to hear the appeal. The Supreme Judicial Court agreed.


The first issue the court looked at was whether there was a scientific consensus on the efficacy of FSTs in determining if a driver was impaired by marijuana. The court found none, stating that “[t]here is ongoing disagreement among scientists . . . as to whether the FSTs are indicative of marijuana impairment.” The court looked at numerous studies that have been conducted on the issue. These studies reached varying conclusions with some finding a correlation between the performance of the FSTs and marijuana impairment and others finding none. Thus, the court found that “the scientific community has yet to reach a consensus on the reliability of FSTs to assess whether a driver is under the influence of marijuana.” The court determined that it was “not persuaded . . . that the FSTs can be treated as scientific tests establishing impairments 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 to marijuana use or impairment.”

The court then looked at whether FSTs still had probative value in a DUI-Marijuana case in a different capacity. The court found that they did, stating that the tests “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.” The court further concluded that “[w]e 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.”

Thus, an officer could testify, as a layperson, as to how a defendant performed on an FST but could not state that the test showed the defendant was under the influence of marijuana. Nor could the officer state whether the “defendant ‘passed' or ‘failed' any FST, as this language improperly implies that the FST is a definitive test of marijuana use or impairment.” In addition, the court stated that “[i]n all circumstances . . . it must be made clear to the fact finder that the [FSTs] do not directly test marijuana impairment.” Rather the tests are “a means of evaluating a defendant's balance, coordination, and other skills specific to that test.” The court also stated that the tests should be referred to as roadside assessments rather than field sobriety tests “so as to not suggest that they function as scientific validation of a defendant's sobriety or intoxication.”

Another key point the court made was that as the FSTs “cannot be treated as scientific ‘tests' of impairment means that evidence of performance on FSTs, alone, is not sufficient to support a finding that the defendant's ability to drive safely was impaired due to the consumption of marijuana, and the jury must be so instructed.”

The court also concluded that an officer could not testify as an expert about “the effects of marijuana consumption" and could not "offer an opinion that a defendant was intoxicated by marijuana.” The court reasoned that, while the effects of alcohol are common knowledge, marijuana is different. The studies had not found a specific set of characteristics that all those high on marijuana display. The court concluded that "[w]here there is no scientific consensus on what, if any, physical characteristics indicate marijuana intoxication, no lay opinion can be admissible as common knowledge or understanding on that subject." However, the court did determine that "[a] lay witness may testify concerning a defendant's observable appearance, behavior, and demeanor, but may not offer an opinion as to the defendant's sobriety or intoxication."

In addition, the court stated that jurors “may use their common sense in evaluating whether the Commonwealth introduced sufficient evidence to satisfy the burden of proof.”

Finally, the court summarized its findings and remanded the case to the District Court.

If you have been charged with a DUI for driving under the influence of marijuana, contact Georgia DUI Attorney Richard Lawson today to discuss your case. ​We never assume a person is guilty just because they have been charged. Do not face severe Georgia DUI Penalties without first calling our office. 

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Richard Lawson

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