Under Massachusetts OUI Law, the prosecutor does not have to prove that alcohol is the sole cause of the impairment.  I had this issue in a recent trial where the Commonwealth was attempting to allege that my client was impaired through the combined impact of alcohol and marijuana.  

        The Massachusetts Supreme Judicial Court decided the case of Commonwealth v. Stathopoulus, 401 Mass. 453 (1988), which held that the Commonwealth is entitled to a jury instruction as follows:  

If you find that the alcohol which the defendant may have ingested alone did not render him under the influence of alcohol, but the mixture of that alcohol with a controlled substance, diminished his ability to operate a motor vehicle safely, you are warranted in finding him guilty.  

The SJC held that alcohol only needs to be one contributing cause toward a reduced ability to operate a motor vehicle safely.  The SJC held that alcohol does not have to be the sole or exclusive cause.  

This jury instruction can be very damaging toward the defense.  There are several objection that can be made to this instruction.  

A case that is related to this issue is the case of Commonwealth v. Shellenberger, 64 Mass. App. Ct. 70 (2005), in that case the prosecutor tried to argue that the defendant was impaired by amphetamines, based on a lab result that showed a positive result for amphetamines.  The Appeals Court found that there was no evidence to support that the defendant was operating under the influence of amphetamines.  To prove this the Commonwealth would have to show reliable evidence as to the amount or concentration of the drug in the defendant’s system and expert testimony indicated that at that concentration the drug would impair the defendant.  The Massachusetts Appeals Court referenced another Appeals Court decision, helpful to the defense, Commonwealth v. Johnson, 59 Mass. App. Ct. 164 (2003), where the Court found a urine screen was improperly admitted into evidence, leaving the jury to speculate as to the meaning of the results. 

In light of Commonwealth v. Gerhardt, 477 Mass. 775 (2017), and these Appeals Court decisions, a Massachusetts OUI Lawyer could make a strong argument that mere admission to consumption of a prescription drug or marijuana, should not be enough to permit a jury to infer that, the substance contributed to the defendant’s impairment.  

The Stathopoulus jury instruction should be objected to as it as very prejudice and invites the jury to speculate that there is impairment.  The Commonwealth should be required to present expert testimony to show that another substance impaired a defendant along with alcohol rather than leaving it to the jury to make that assumption.

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