Massachusetts Appeals Court Reverses OUI Manslaughter Conviction Over Substitute-Expert Blood Alcohol Testimony

The Massachusetts Appeals Court recently addressed an important confrontation-clause issue involving blood alcohol testing in Commonwealth v. Misael Sanchez, Appeals Court No. 24-P-1408 (Aug. 18, 2026). The decision is particularly useful for criminal defense lawyers dealing with substitute forensic experts: a prosecutor cannot avoid the defendant’s right to confront the analyst who actually performed forensic testing simply by having another scientist review the work and offer an opinion from it.

There is an important limitation at the outset. Sanchez was issued as a memorandum and order under Appeals Court Rule 23.0. That matters. Rule 23.0 decisions may be cited for their persuasive value, but they are not binding precedent. The Appeals Court itself warns that these decisions are directed primarily to the parties, may not fully set out the facts or the panel’s reasoning, are not circulated to the entire court, and represent only the views of the particular panel deciding the case.

So Sanchez should not be cited as though it announced some new, binding rule governing substitute experts. It did not. The controlling Massachusetts authority is Commonwealth v. Gordon, 496 Mass. 554, 575 & n.25 (2025). What Sanchez provides is a useful and potentially powerful application of Gordon—particularly when the Commonwealth argues that improperly admitted forensic evidence was harmless.

The Case

Sanchez arose from a fatal motor vehicle crash in Springfield. According to the Appeals Court, the defendant was driving at an extraordinarily high rate of speed shortly before the collision. Crash data showed that the vehicle was traveling ninety-three miles per hour four seconds before impact and approximately sixty-five miles per hour when it struck the victim’s vehicle.

There was also substantial evidence that Sanchez had consumed alcohol. Witnesses smelled alcohol. Beer bottles were found in and around the vehicle. Witnesses testified that Sanchez attempted to dispose of beer after the crash, and his hospital records described him as “clinically intoxicated.”
But the Commonwealth also had something much more powerful: a blood alcohol number.

Police obtained Sanchez’s hospital blood pursuant to a warrant. State Police analyst Hilary Griffiths performed the relevant testing, including gas chromatography testing. Griffiths, however, did not testify at trial. Instead, forensic scientist Hannah Knowles testified as a substitute expert. Knowles had witnessed one alcohol diffusion test, but she did not witness Griffiths perform the gas chromatography testing. Relying upon Griffiths’s work, Knowles told the jury that Sanchez’s blood alcohol concentration was approximately .207.

That created the confrontation problem.

Gordon and the Problem With the Substitute Expert

In Commonwealth v. Gordon, 496 Mass. 554, 575 & n.25 (2025), the Supreme Judicial Court addressed the confrontation-clause problem created when a testifying expert’s opinion depends upon testimonial statements generated by a nontestifying forensic analyst.

The problem is not solved merely by having a second analyst review the work and present an “independent” opinion. If the testifying expert’s opinion depends upon the truth of testimonial statements made by the analyst who actually performed the testing, the defendant has a confrontation right that cannot simply be bypassed by substituting another witness.

In Sanchez, the Commonwealth conceded that Knowles’s testimony had been admitted in error under Gordon. The real fight on appeal was therefore not whether constitutional error had occurred. It had. The question was whether that error was harmless beyond a reasonable doubt.

That is where the decision becomes particularly interesting.

The Jury Did Not Convict Under the .08 Theory. That Did Not Make the Error Harmless.

The trial judge gave the jury two possible ways to find the OUI component of manslaughter while OUI: that Sanchez was actually under the influence of alcohol, or that his blood alcohol concentration was .08 or greater.

The jury convicted under the impairment theory. It did not convict under the .08 theory.

That gave the Commonwealth an obvious appellate argument: even if the .207 BAC testimony should not have come into evidence, the jury had rejected the per se .08 theory anyway. There was also plenty of other evidence suggesting alcohol consumption and impairment.

The Appeals Court was not persuaded.

The problem was that a .207 blood alcohol reading was not neatly confined to the per se theory. It was enormously powerful circumstantial evidence on the separate question whether alcohol had diminished Sanchez’s ability to drive safely. The court described the BAC evidence as the strongest evidence of intoxication and noted the prosecutor’s repeated reliance upon it. The prosecutor actually began closing argument by telling the jury: “93 miles an hour and a 0.207 blood alcohol level. That’s what this case is about.”

That matters.

When courts conduct harmless-error review, they do not simply count the remaining pieces of admissible evidence and ask whether there was still enough evidence to convict. The question is whether the Commonwealth can establish beyond a reasonable doubt that the constitutional error did not influence the jury, or had only a very slight effect.

And where the prosecutor has taken the improperly admitted evidence and made it a centerpiece of the case, that burden becomes considerably harder to carry.

The Appeals Court concluded that the Commonwealth had not met it. The BAC result was too powerful, and too important to the prosecution’s presentation of intoxication, for the court to say beyond a reasonable doubt that its improper admission did not affect the verdict. The portion of the conviction depending upon proof of intoxication therefore could not stand.

The Limits of Sanchez as Authority

Sanchez is worth reading, but it is equally important not to overstate what it holds.

Because this is a Rule 23.0 decision, it is persuasive authority, not binding precedent. That limitation appears on the first page of the decision itself. A Rule 23.0 decision may be cited for whatever persuasive value it has, but it does not bind another panel of the Appeals Court, the Superior Court, or the District Court in the same way as a published appellate opinion.

More importantly, Sanchez does not create the rule prohibiting this type of substitute-expert testimony. That rule comes from Commonwealth v. Gordon, 496 Mass. 554, 575 & n.25 (2025), and the confrontation-clause principles applied there.

Sanchez is useful for something somewhat different. It demonstrates how that rule may operate when a reviewing court evaluates prejudice.

The case shows that the Commonwealth cannot necessarily save an unconstitutional forensic opinion by pointing to other evidence of impairment. Nor does the jury’s rejection of a numerical BAC theory automatically establish that the improperly admitted BAC number played no role in its consideration of an impairment theory. Courts look at the evidence in the context in which the jury actually received it—including how prominently the prosecutor used it.

That is a significant point for defense lawyers litigating forensic evidence.

The Conviction Was Not Simply Wiped Away

There is one other important limitation to the result.

The Appeals Court concluded that the evidence of Sanchez’s driving—particularly evidence that he was traveling ninety-three miles per hour in a thirty-five-mile-per-hour zone shortly before the fatal collision—was overwhelming evidence of wanton or reckless conduct independent of the improperly admitted BAC testimony. It therefore concluded that the evidence supported the lesser included offense of involuntary manslaughter.

The court vacated the judgment and set aside the verdict, but on remand the Commonwealth may seek sentencing on the lesser included offense of involuntary manslaughter or elect to retry Sanchez for manslaughter while OUI.

That makes Sanchez neither a sweeping defense victory nor a broad new confrontation-clause decision. It is something more precise.

Gordon supplies the constitutional rule. Sanchez illustrates its consequence when inadmissible forensic evidence becomes one of the prosecution’s most powerful pieces of evidence and is featured as such before the jury. Even in a case containing substantial independent evidence of alcohol consumption, the Commonwealth still bears the demanding burden of proving that constitutional error was harmless beyond a reasonable doubt.

For Massachusetts criminal defense lawyers confronting substitute laboratory witnesses, that is the part of Sanchez worth remembering.

Benzaken, Sheehan & Wood, LLP represents people charged with serious criminal offenses throughout Massachusetts, including OUI offenses, vehicular homicide cases, and cases involving forensic and scientific evidence. Questions about a criminal case can be directed to our Brockton office.