The Substitute Analyst and the Right of Confrontation in Massachusetts Drug Cases

By Attorney Joe Serpa | Georgetown University Law Center | 30 Years Massachusetts Criminal Defense

Forensic evidence drives many drug prosecutions. To prove that a substance is a particular controlled substance, the Commonwealth relies on analysis performed at a crime laboratory. The right of confrontation controls how that analysis comes into evidence, and a 2025 decision of the Supreme Judicial Court limits the use of a substitute analyst who did not perform the test. This post explains the rule and how the defense applies it. It supplements the firm’s pages on Massachusetts drug charges and on cross-examination.

The Testimonial Certificate

A certificate that reports the result of a drug analysis is testimonial, because it is prepared for use in a criminal prosecution. The Commonwealth cannot prove its case by handing the jury such a certificate. The analyst who performed the test must testify and face cross-examination. Melendez-Diaz v. Massachusetts, 557 U.S. 305 (2009). This rule gives the accused the chance to test the reliability of the analysis through the witness who produced it.

Smith v. Arizona and Commonwealth v. Gordon

The Commonwealth sometimes responds by calling a substitute analyst, a witness who did not perform the original test but reviews the file and offers an opinion. The United States Supreme Court addressed that practice in Smith v. Arizona, 602 U.S. 779 (2024), and the Supreme Judicial Court applied Smith in Commonwealth v. Gordon, 496 Mass. 554 (2025). The court held that the confrontation clause bars a substitute expert from offering an opinion that depends on the truth of a nontestifying analyst’s testimonial statements, such as the notes describing the sample and the testing protocol, even when the substitute is familiar with the laboratory’s procedures and has reviewed the case file. In that situation the witness against the accused is the absent analyst, and the accused has the right to confront that analyst.

The Limit: Independent Review of Machine Data

The rule has a boundary. An expert who independently reviews raw, machine-generated data, such as the output of a gas chromatograph-mass spectrometer, and testifies to conclusions based on training and experience does not violate the confrontation clause, because a machine printout is not a statement by a person. Commonwealth v. Souza, 494 Mass. 705 (2024). The distinction is between a witness who forms an independent opinion from the underlying data and a witness who serves as a conduit for an absent analyst’s conclusions.

How the Defense Uses the Rule

Cross-examination is how the defense determines whether a witness formed an independent opinion or served as a conduit for an absent analyst. The examination establishes what the witness personally did, what the witness knows only from the absent analyst’s notes, and whether the opinion rests on the truth of those notes about the sample, the procedure, and the protocol. When the answers show that the opinion cannot stand without the absent analyst’s testimonial statements, the opinion is not admissible, and the forensic result may be excluded. The exclusion of the analysis can leave the Commonwealth without proof of an essential element.

Attorney Serpa defends drug charges across the Massachusetts District Courts and the Boston Municipal Court. For a confidential consultation, call 617.936.0201.