Massachusetts case law states that field sobriety tests cannot scientifically conclude that a driver is sober or impair.
Similarly, an officer who administers the field sobriety test cannot testify as an expert witness at trial.
Instead, the officer’s observations must be limited to those of a lay witness.
The key case on this issue is Commonwealth v. Moreno, 102 Mass. App. Ct. 321, 324 (2023).
The pertinent section of that opinion states,
an opinion regarding a defendant’s sobriety is a lay opinion, and a police officer may testify as a non-expert witness to a defendant’s “apparent intoxication. Typical field sobriety tests do not supply the basis for a scientific opinion about whether a person is under the influence of alcohol or the level of intoxication. Instead, field sobriety tests permit an officer to observe whether a person has lost or diminished balance, coordination, or mental acuity due to intoxication. Because a lay juror understands the effects of intoxication, an officer’s observations of a defendant’s behavior during a sobriety test remain within the realm of common experience. [Additionally,] a prosecutor who elicits from a police officer his or her special training or expertise in ascertaining whether a person is intoxicated risks transforming the police officer from a lay witness to an expert witness on this issue. (Citations and quotation omitted.)
To read the full text of Moreno, click here.