Criminal Law—Supreme Judicial Court of Massachusetts Fails to Require Statistical Analysis for Nonexclusion DNA Test Results—Commonwealth v. Mattei, 920 N.E.2d 845 (Mass. 2010)

Massachusetts grants judges broad discretion when determining the relevancy of evidence.  The Massachusetts Guide to Evidence Section 403 (Section 403) states that relevant evidence is admissible unless the trial judge believes the probative value of the evidence is substantially outweighed by the danger of unfair prejudice to the defendant.  Massachusetts judges apply a case-by-case approach in weighing the prejudicial effect of deoxyribonucleic acid (DNA) test results presented to a jury absent supporting testimony regarding the statistical accuracy of such results.  In Commonwealth v. Mattei, the Massachusetts Supreme Judicial Court (SJC) addressed whether DNA test results that failed to exclude an individual as a possible contributor to the DNA sample were admissible without an accompanying probability analysis.  Although the SJC held that the nonexclusion test results were improperly admitted, it failed to require that supporting statistical testimony is always necessary to admit such results. . .