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OUI drugs in Massachusetts: How the District Attorney prosecutes these cases in Court

After the Massachusetts Supreme Judicial Court decided the case of Commonwealth v. Gerhardt, many wondered how the Commonwealth would prove OUI Marijuana cases in Court.  Charges involving OUI drugs, including marijuana are difficult to prove.  However, these cases are still being prosecuted in the court.

The SJC in Gerhardt did not exclude field sobriety tests, now referred to as assessments from being offered into evidence in Court.  It placed limitations on how this evidence can be presented to the jury and what its ultimate weight should be in assessing whether the Commonwealth has proven the case beyond a reasonable doubt.   OUI marijuana cases will be prosecuted based on the observations of the driving, the field tests, admissions of the person consuming marijuana, the smell of marijuana, evidence of drugs found in the car.

This case was the first case to hold that field sobriety tests are not scientific tests of impairment by marijuana and that a jury should get a cautionary instruction when presented with this evidence.  The Court also held that officers could not testify as lay witnesses that someone was impaired by marijuana. 

The SJC held that the jury should be told that field sobriety assessments are not scientific tests of impairment by marijuana.  The Court could that there were no studies that show a correlation between performance on the field tests and impairment by marijuana and that the studies were inconclusive. The SJC held that they should be referred to as roadside assessments instead of tests and without reference to any pass or fail language. To read the Gerhardt decision visit the Justia website.

Court let the field tests into evidence because the court said the standard for admissible evidence is very low.  So to the extent that those exercise are relevant to driving a jury can consider them as evidence,  However, the SJC imposed a cautionary instruction that field sobriety tests standing alone cannot support a conviction beyond a reasonable doubt.

With field sobriety tests given a diminished weight in OUI marijuana cases, how will prosecutor attempt to prove these charges in Court.


A key part of the Gerhardt decision is that the Court found that officers could not testify to their lay opinion that someone was impaired by marijuana. The Court found the manner in which marijuana impacts a person is not subject to common knowledge such that the Court could allow a lay opinion regarding an individual’s sobriety.  The Court did say that officer may testify about observations, behavior and demeanor, but cannot offer an opinion as to sobriety.  The SJC opened the door for the Commonwealth to prove these cases by stating that the jury can use its common sense; the jury hear all the evidence without any opinion and be allowed to decide for itself whether the person is impaired.

DRE Testimony from Drug Recognition Expert 

In some cases the police may call a DRE, Drug Recognition Officer to Render an opinion that the individual is impaired by marijuana.  The Massachusetts Supreme Judicial Court has not addressed whether this testimony would meet the standard for admissibility in Massachusetts.  Many Courts across the United States have allowed the testimony into evidence; however a notable case from Maryland State v. Brightful found that DRE testimony did not meet the standard of scientific reliability.

Given the Gerhardt decision, prosecutors may have a difficult time establishing the scientific reliability of DRE testimony. First, the DRE procedure relies on the field sobriety tests as a component of the exercise. Further, it requires the officers to use the 12 steps procedure to rule out a medical cause of the impairment and determine which drug caused the impairment.  This is beyond the expertise of a police officer.  It essentially requires the officers to make a medical assessment.  As part of the 12 steps, the officers ask the person what drug the person has consumed.  The officers opinion comes back to reflect the admission obtained from the defendant.  When officers were given a DRE exam, without interrogating the suspect, the Shiner Study showed that the officer’s opinion was less than 50% accurate.

Part of the DRE 12 steps involves examining the eyes with 3 different eye exams, HGN, VGN and lack of convergence test.  In Massachusetts under the case of Commonwealth v. Sands, expert testimony is required to admit the HGN test.  The Gerhardt case further stressed that expert testimony is even more important as whether nystagmus is called by a particular drug is not the product of lay opinion.  Officers are simply not qualified to make medical assessments about an individual’s eyes.

Breath Test for Marijuana 

With the increase legalization of marijuana, and the difficulty in improving impairment, companies are aggressive trying to perfect a marijuana breath test.  Hound Labs in California claims to have perfected a marijuana breath test in an article on the MPR news website.  The lab claims that it can detect marijuana that was ingested within the last two hours.  This window is considered the peak time frame that THC would be within the blood.  

Creating a breath test for marijuana is more complex than for alcohol because the metabolites of THC can remain in the blood long after the person smoked.  

Since THC effects the body different from alcohol, there is no agreement on the level of THC that case impairment.  Some States that created per se limits of THC in the blood making it a crime to drive above these limits regardless of actual impairment.   In Massachusetts, there are likely to be legislative and technological changes that impact prosecutions of OUI drugs coming in the next few years.  This is an evolving area of the law intersecting science, technology and new public policy legalizing marijuana.  

To learn more about defending OUI drugs cases in Massachusetts, visit our website with extensive information on this topic.



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