Mass. R. Evid. 703
The facts or data in the particular case upon which an expert witness bases an opinion or inference may be those perceived by or made known to the witness at or before the hearing. These include (a) facts observed by the witness or otherwise in the witness's direct personal knowledge; (b) evidence already in the record or that will be presented during the course of the proceedings, which facts may be assumed to be true in questions put to the witness; and (c) facts or data not in evidence if the facts or data are independently admissible in evidence and are a permissible basis for an expert to consider in formulating an opinion.
Mass. Guid. Evid. 703
This section is derived from Department of Youth Servs. v. A Juvenile, 398 Mass. 516, 531 (1986); LaClair v. Silberline Mfg. Co., 379 Mass. 21, 32 (1979); and Commonwealth v. Russ, 232 Mass. 58, 73 (1919). See Commonwealth v. Piantedosi, 478 Mass. 536, 541-546 (2017). Unlike Fed. R. Evid. 703, which permits opinions based on inadmissible evidence of a type reasonably relied upon by experts in the relevant field, Massachusetts law requires the facts or data underlying an opinion to be independently admissible, even if not actually admitted. Department of Youth Servs. v. A Juvenile, 398 Mass. at 530-531. An opinion may be based on a combination of the three sources of facts or data set forth in this section. See, e.g., Commonwealth v. Gallett, 481 Mass. 662, 682 (2019) (medical examiner may testify that type of injury he personally observed was consistent with Commonwealth's theory, presented in a hypothetical question, based on facts in evidence, of manner in which injury was inflicted).
Opinion Based on Personal Knowledge. An expert may base an opinion on facts within the expert's personal knowledge. Commonwealth v. Kolenovic, 478 Mass. 189, 205 (2017) (facts within personal knowledge include tests performed or supervised by the expert); Sacco v. Roupenian, 409 Mass. 25, 30 (1990) (physician's opinion about progress of cancer based on observations during treatment); McLaughlin v. Bernstein, 356 Mass. 219, 222 (1969) (examination of machine). Compare Commonwealth v. Barbosa, 477 Mass. 658, 667-669 (2017) (expert properly testified, based on personal knowledge, that defendant belonged to gang), with Commonwealth v. Wardsworth, 482 Mass. 454, 466-470 (2019) (reversible error for expert to testify that defendant was gang member based solely on personal observations that defendant associated with suspected gang members).
Opinion Based on Evidence in the Record. An expert may testify, in response to a hypothetical question or otherwise, to an opinion that is based on evidence already admitted. Commonwealth v. Burgess, 450 Mass. 422, 435-436 (2008). The trial judge may permit an expert to express an opinion de bene based on counsel's representation that evidence of the supporting facts will be introduced later in the trial. Harris-Lewis v. Mudge, 60 Mass. App. Ct. 480, 485-486 (2004). If such evidence is not forthcoming, the court should strike the opinion and instruct the jury to disregard it. Id. If the opposing party fails to move to strike the opinion, it may be considered for whatever probative value the jury deems appropriate. Wilborg v. Denzell, 359 Mass. 279, 283 (1971); Commonwealth v. Salyer, 84 Mass. App. Ct. 346, 356 (2013).
When there is a factual dispute, a hypothetical question posed to an expert witness must identify which set of facts or portions of the record form the basis for the expert's opinion. See Connor v. O'Donnell, 230 Mass. 39, 42 (1918). A hypothetical question that misstates the evidence is properly excluded. Commonwealth v. Rosario, 21 Mass. App. Ct. 286, 289 (1985).
Opinion Based on Independently Admissible Evidence. An expert witness may base an opinion on facts or data that would be admissible, even if not actually admitted at trial. The facts or data must be of the type relied upon by experts in the field. Department of Youth Servs. v. A Juvenile, 398 Mass. 516, 528-531 (1986). In determining whether facts or data are independently admissible, the court must determine whether the underlying facts or data would potentially be admissible in any form through appropriate witnesses. Such witnesses need not be immediately available in court to testify. See Commonwealth v. Markvart, 437 Mass. 331, 337-338 (2002). But see Custody of Michel, 28 Mass. App. Ct. 260, 265-267 (1990) (permitting broader basis for testimony and reports of court-appointed investigators under G. L. c. 119, § 24). Thus, a psychologist called by the defense in a murder trial could opine on the defendant's mental impairment at the time of the offense based on the witness's interview with the defendant five weeks after the killings and the contents of police and medical records, but not on the basis of a psychiatrist's earlier "preliminary diagnosis" that was not shown to be reliable and independently admissible. Commonwealth v. Waite, 422 Mass. 792, 803-804 (1996).
An expert who relies on independently admissible facts that are not in evidence is not ordinarily permitted to testify to the basis of the opinion on direct examination. Commonwealth v. Ronchi, 491 Mass. 284, 301 (2023). Further, "an expert witness may not, under the guise of stating the reasons for his opinion, testify to matters of hearsay in the course of his direct examination unless such matters are admissible under some statutory or other recognized exception to the hearsay rule." Commonwealth v. Nardi, 452 Mass. 379, 392 (2008), quoting Grant v. Lewis/Boyle, Inc., 408 Mass. 269, 273 (1990). See Matter of J.P., 486 Mass. 117, 122 n.11 (2020) (on direct examination, expert may not testify about statements within medical record that formed basis of expert's opinion where record itself was not admitted). But see Commonwealth v. Asenjo, 477 Mass. 599, 607-609 (2017) (error to exclude expert testimony regarding battered woman syndrome where G. L. c. 233, § 23F, provides independent statutory basis for admission of evidence; statute is more permissive than common law embodied in Section 703 and permits expert testimony based solely on defendant's assertion of certain specified defenses).
The limitation on the direct-examination testimony of expert witnesses operates in both civil and criminal cases and applies to both sides. Vassallo v. Baxter Healthcare Corp., 428 Mass. 1, 15-16 (1998). See Commonwealth v. Chappell, 473 Mass. 191, 204 (2015) (this evidentiary rule does not violate defendant's right to present a full defense). On cross-examination, the opposing party may choose to elicit the complete basis for an expert's opinion, including whether any underlying facts or data where not from personal knowledge. Nardi, 452 Mass. at 390. Even if an expert is aware of certain facts not in evidence, a judge may exclude reference to those facts as unfairly prejudicial if they were not relied upon as part of the expert's opinion, do not clarify or discredit the opinion, and serve only to focus the jury on those facts. Commonwealth v. Anestal, 463 Mass. 655, 667-668 (2012) (prior bad acts excluded). The decision to elicit admissible facts not in evidence that form the basis for an expert's opinion belongs solely to the opposing party, and it is improper for the judge to request testimony about those facts. See Matter of P.R., 488 Mass. 136, 142-144 (2021) (reversible error to permit psychiatrist to testify on direct examination to hearsay basis for his opinion, even when basis was solicited at trial judge's request).
Cross-Reference: Section 705, Disclosure of Facts or Data Underlying Expert Opinion.
Substituted Experts and the Confrontation Clause. Hearsay statements of fact and opinion contained in forensic reports-such as drug certificates, autopsy reports, and DNA analy-ses-created to be used against the accused in investigating or prosecuting a crime are inadmissible against the defendant in a criminal case unless the author is present in court and subject to crossexamination or there was a prior opportunity for cross-examination. Melendez-Diaz v. Massachusetts, 557 U.S. 305, 309-311 (2009); Commonwealth v. Nardi, 452 Mass. 379, 391-394 (2008). However, a "substitute expert," that is, an expert witness who did not author or create the report, may testify to the expert's own opinion based on the tests and data contained in another analyst's report without violating the confrontation clause, so long as the substitute expert does not testify to or assert the truth of the author's statements, observations, or opinions. See Commonwealth v. Grady, 474 Mass. 715, 716 (2016) (substitute chemist/drug analyst); Commonwealth v. Chappell, 473 Mass. 191, 201-202 (2015) (substitute DNA analyst); Nardi, 452 Mass. at 387-394 (substitute medical examiner).
Meaningful Opportunity to Cross-Examine. The Massachusetts common law of evidence is more protective of confrontation rights than the Sixth Amendment to the United States Constitution in that it requires that the defendant have "a meaningful opportunity to cross-examine the expert about her opinion and the reliability of the facts or data that underlie her opinion." Commonwealth v. Tas-sone, 468 Mass. 391, 399-402 (2014). Thus, in Tassone, the court held that where the substitute DNA analyst was not affiliated with the laboratory where the DNA testing was conducted and there was no showing that she had any personal knowledge of that lab's evidence-handling protocols, the defendant was denied the opportunity to explore through cross-examination whether the testing was flawed. The court distinguished Commonwealth v. Greineder, 464 Mass. 580 (2013), where the substitute DNA expert was the forensic laboratory director of the facility where the DNA testing was conducted and was personally aware of the DNA testing process employed by the laboratory. See also Commonwealth v. Barry, 481 Mass. 388, 407-408 (2019) (director of laboratory that conducted DNA testing was not substitute expert, despite not being person who physically tested samples, because he participated in analysis of samples and testified about report detailing his conclusions). Compare Commonwealth v. Sanchez, 476 Mass. 725, 734 (2017) (fire inspector who was present for electrician's inspection of arson site could testify and be meaningfully cross-examined about his own observations), with Commonwealth v. Jones, 472 Mass. 707, 715-716 (2015) (where DNA expert's knowledge of how DNA samples had been collected was derived from form completed by person who had collected the specimens from victim's body, no meaningful opportunity to cross-examine witness).
DNA Analyst. Where the prosecution offers an opinion about a DNA profile match, "a meaningful opportunity for cross-examination means that a defendant must have the opportunity substantively to explore the 'risk of evidence being mishandled or mislabeled, or of data being fabricated or manipulated, and . . . whether the expert's opinion is vulnerable to these risks.'" Tassone, 468 Mass. at 400, quoting Commonwealth v. Barbosa, 457 Mass. 773, 791 (2010), cert. denied, 563 U.S. 990 (2011). If the prosecution does not call the DNA analyst who conducted the testing as a witness, it must, at a minimum, call an expert affiliated with the laboratory where the testing took place. Tassone, 468 Mass. at 402. Where the testifying expert has personal knowledge of the testing laboratory's procedures, the witness may give an opinion about a DNA match, even though the basis is in whole or in part evidence collected or created by an absent DNA analyst. See Greineder, 464 Mass. at 583-584. An expert who has no knowledge of how the sample was collected cannot testify to the location from which the sample was collected. Jones, 472 Mass. at 716-717 n.3 (no meaningful opportunity to cross-examine testifying DNA expert about how specimen was collected).
Medical Examiner. A substitute medical examiner may offer an opinion even though it is based in whole or in part on evidence collected or created by the absent medical examiner. See Commonwealth v. Seino, 479 Mass. 463, 466-468 (2018) (substitute medical examiner may offer opinion as to cause of death based upon review of independently admissible documents contained in original medical examiner's file); Commonwealth v. Nardi, 452 Mass. 379, 388 (2008). The original autopsy report, notes, and photographs provide the defendant with a "meaningful opportunity" to cross-examine the substitute witness about possible flaws in the substitute's own opinion. Tassone, 468 Mass. at 400. The Commonwealth is not required to show that the medical examiner who performed an autopsy is unavailable for a substitute medical examiner to testify. Commonwealth v. Leiva, 484 Mass. 766, 792 (2020).
Section 702, Testimony by Expert Witnesses; Section 705, Disclosure of Facts or Data Underlying Expert Opinion; Introductory Note to Article VIII, Hearsay.