Criminal law - inconclusive DNA test results admitted as relevant evidence despite absence of random match probability analysis - Commonwealth v. Mattei.

• Author: O'Malley, Ryan Patrick
• Position: Massachusetts

The Commonwealth of Massachusetts's current standard for admissibility of scientific evidence at trial is based on relevancy and reliability. (1) The first successful evidentiary use of deoxyribonucleic acid ("DNA") test results in a criminal trial in the United States occurred in 1987, but the Supreme Judicial Court of Massachusetts ("SJC") did not address the issue until 1991. (2) In Commonwealth v. Mattei, (3) the Massachusetts Court of Appeals considered the admissibility of inconclusive DNA test results in a criminal trial. (4) The court improperly concluded that the inconclusive DNA test results were admissible as relevant evidence despite the lack of a statistical probability analysis of the likelihood that a match occurred by chance. (5)

Following a jury trial, Defendant Alexander Mattei was convicted of numerous crimes, including assault with intent to rape. (6) At trial, the Commonwealth of Massachusetts ("Commonwealth") produced evidence of DNA samples that were recovered during the police investigation of the crimes. (7) The Commonwealth's expert testified that neither Mattei nor the victim could be definitively identified or excluded as a source of the DNA because some of the samples contained mixtures of DNA from more than one person. (8) At no time did the Commonwealth's expert provide any information of the statistical probability that either Mattei's or the victim's DNA was a random match to the samples taken from the crime scene. (9)

Despite the inconclusive test results and lack of accompanying statistical analysis, the trial judge admitted the DNA samples and expert testimony into evidence over the objection of Mattei's counsel. (10) On appeal, Mattei argued that the inconclusive DNA test results were inadmissible absent a statistical analysis of the likelihood of a potential random match. (11) The appeals court nonetheless upheld the trial judge's admission of the inconclusive DNA test results, concluding that such evidence was relevant. (12)

Relevant evidence is admissible in the courts of the Commonwealth unless its probative value is substantially outweighed by its prejudicial effect, it confuses the issues, or it has the potential to mislead the jury. (13) The standard for relevancy is extremely broad and trial judges are afforded substantial discretion in their rulings. (14) Undoubtedly, DNA test results are relevant evidence in criminal cases, but courts historically restricted their admissibility on other grounds. (15) In addition to relevancy, a trial judge's ruling on the admissibility of DNA test results is based on the reliability of the underlying testing process. (16) The intricate nature of DNA profiles allows the proponent of DNA evidence to call an expert witness to testify at trial to assist the trier of fact in interpreting DNA test results. (17)

In 1994, the SJC established the valid admission of expert testimony regarding the statistical probability of a "match" obtained from DNA testing. (18) The SJC has repeatedly and unequivocally held that testimony of a DNA "match" must be accompanied by a statistical analysis of the probability of a random match. (19) Evidence of a non-match, however, is admissible without any statistical support. (20) The admissibility of DNA test results as evidence in the courts of the Commonwealth is considered on a case-by-case basis via a voir dire hearing. (21) Employing this approach in recent decisions, the SJC has upheld the admission of otherwise inconclusive DNA test results as relevant evidence. (22) Nevertheless, in order to be admissible at trial, inconclusive DNA evidence must be probative of an issue in the case. (23)

The law in most states concerning the admissibility of DNA statistical probability evidence is in unison with that of the Commonwealth. (24) In contrast, some jurisdictions, under particular circumstances, permit an expert to testify to a DNA match without providing a numerical statistical analysis of the probability that the match occurred randomly. (25) The admission of both qualitative and quantitative statistical probability testimony undoubtedly creates the possibility of unfair prejudice and misleading of the jury. (26) This prejudicial and misleading effect, however, is exacerbated if DNA match evidence is admitted without any supporting statistical analysis of a random match probability. (27)

In Commonwealth v. Mattei, (28) the Massachusetts Appeals Court considered whether inconclusive DNA evidence is admissible in a criminal trial without any accompanying statistical analysis of the likelihood of a random match. (29) In deciding the issue, the court drew a comparison to blood type tests commonly used to include or exclude a defendant as a contributor to a blood sample. (30) Consequently, the court opined that an inclusion/exclusion presentation for inconclusive DNA evidence is more appropriate and beneficial to all defendants, as opposed to conditioning admissibility on a statistical probability analysis. (31) Based on this newfound standard, the court upheld the admission of the inconclusive DNA evidence noting that it was not presented to the jury as a "match." (32) Although the DNA evidence could not definitively identify or exclude Mattei or the victim as contributors, the court held that it was nevertheless admissible because it provided general descriptive information about the perpetrator. (33) Relying on two recent SJC decisions that upheld the admission of inconclusive DNA evidence, the court opined that the issue before it was one of relevancy and, therefore, afforded the trial judge's decision substantial deference. (34)

Taking exception to the failure of the Commonwealth's expert to provide a statistical analysis, the dissenting opinion impliedly criticized the majority's summary dismissal of nearly two decades of precedent. (35) While cautioning against the indiscriminate use of inconclusive DNA evidence without statistical support, the dissent stated that there is a substantial risk of misinterpreting such evidence as definitively inculpatory. (36) The dissent emphasized that the rule requiring statistical support for DNA "match" testimony is of the utmost importance in instances where the probability of a match is extremely low compared to cases in which DNA evidence definitively identifies the defendant as the source. (37) Accordingly, the dissent argued that inconclusive DNA test results are admissible only if accompanied by a statistical analysis of the likelihood that a match occurred by chance. (38)

In Commonwealth v. Mattei, the Massachusetts Appeals Court incorrectly upheld the admission of DNA match testimony without requiring a statistical probability analysis. (39) The rationale behind the statistical analysis requirement is to regulate the use of DNA evidence at trial and provide the trier of fact with an understanding of a DNA match. (40) In reaching its decision, the court neglected to adhere to nearly two decades of established precedent and failed to provide any logical reasons for its divergence. (41) The court's reliance on recent SJC decisions as support for its reasoning is misplaced, as these opinions merely suggest that inconclusive DNA test results are relevant evidence, not that such evidence is admissible without any supporting statistical analysis. (42) As a result, the court misconstrued the issue before it as one of mere relevancy and failed to consider whether the probative value of the evidence outweighed the irrefutable and substantial unfair prejudice to Mattei. (43) Furthermore, by applying palpable error instead of abuse of discretion, the court failed to apply the correct legal standard on appellate review for admission of scientific evidence. (44)

By diminishing the prerequisites for admission of DNA "match" testimony, the court's inclusion/exclusion standard carelessly broadens the scope of admissibility of DNA evidence in criminal trials in the Commonwealth. (45) More importantly, the court's ruling ignores the overwhelming significance jurors inherently place on DNA evidence, resulting in unfair prejudice to a criminal defendant. (46) Moreover, this newfound standard unjustly burdens criminal defendants because the jury is deprived of any means for measuring the probative value to afford inconclusive DNA evidence. (47) The absence of a statistical analysis of the probability that a defendant contributed to a DNA sample inhibits jurors from determining the frequency of a particular DNA profile and the meaning of the DNA sample at issue. (48) In suggesting that jurors are capable of evaluating scientific evidence like all forms of evidence, the court failed to recognize a fundamental difference between discernable physical characteristics and intangible scientific evidence. (49) If jurors had the capability that the appeals court impliedly suggests, then expert testimony would not be needed to assist jurors in their evaluation of DNA test results. (50)

Adhering to precedent, the dissent recognized the prejudicial effect DNA evidence has on a jury and provided a logical resolution. (51) Although courts in other jurisdictions have admitted DNA match evidence without statistical support, the statistical probability of a random match was miniscule in those cases. (52) Assuming, arguendo, that an inclusion/exclusion standard is beneficial to defendants as a class, a concurrent requirement of a supporting statistical analysis is nevertheless necessary to combat any misinterpretation or undue weight that might be afforded to inconclusive DNA evidence. (53) Any requirement to the contrary fails to consider the multitude of reasons a DNA "match" may occur and the established precedent in the Commonwealth. (54) The appeals court's current rudimentary standard has the potential to reintroduce unreliable, "junk" science into the courtroom. (55)

The issue before the Massachusetts Appeals Court in Commonwealth v. Mattei was the admissibility of...