The Supreme Judicial Court recently reversed a defendant’s Massachusetts assault and battery conviction, finding that the trial court made a prejudicial error in excluding the defendant’s expert witness. After an altercation with two men, the court indicted the appellant on two counts of assault and battery by means of a dangerous weapon. The defendant argued that he acted in self-defense after one of the men attacked him based on racial animus. To substantiate his claim, the defendant proposed two expert witnesses that could testify that the man had a tattoo of a symbol affiliated with a white supremacist group. The judge excluded the witnesses, and the defendant was convicted.
On appeal, the court considered whether the trial judge incorrectly excluded the defendant’s experts. At trial, the defendant attempted to introduce two experts: one with a doctorate in cultural anthropology who studies the nationalist movement, and another with a doctorate in educational leadership and is an expert on gangs. The defendant argued that the judge’s finding that the experts were not reliable was an abuse of discretion.
Under Massachusetts law, expert testimony works to aid jurors in interpreting evidence that is outside common knowledge. The Daubert-Lanigan standard generally governs the admission of expert testimony. The testimony must stem from a “reliable foundation” and be “relevant to the task at hand” to meet this standard. Evidence is relevant if it tends to make a fact more or less probable.