Supreme Judicial Court (February 15, 2011)
The Supreme Judicial Court issued the following guidelines to ensure that expert forensic ballistics testimony appropriately assists the jury:
1) Before trial, the examiner must adequately document the findings or observations that support the examiner's ultimate opinion, and this documentary evidence, whether in the form of measurements, notes, sketches, or photographs, shall be provided in discovery, so that defense counsel will have an adequate and informed basis to cross-examine the forensic ballistics expert at trial.
2) Before an opinion is offered at trial, a forensic ballistics expert should explain to the jury the theories and methodologies underlying the field of forensic ballistics. This testimony should include, but is not limited to, explanation of how toolmarks are imparted onto projectiles and cartridge casings; the differences between class, subclass, and individual characteristics of firearms; and the different types of resulting toolmarks that examiners look for and compare. Such testimony should also clearly articulate the differences between class and subclass characteristic toolmarks, which can narrow down the group of weapons that may have fired a particular projectile, and individual characteristic toolmarks, which potentially may permit an opinion that a particular firearm fired a projectile.
3) In the absence of special circumstances casting doubt on the reliability of an opinion, and once these two things have been done, a forensic ballistics expert may present an expert's opinion of the toolmarks found on projectiles and cartridge casings. Where a qualified expert has identified sufficient individual characteristic toolmarks reasonably to offer an opinion that a particular firearm fired a projectile or cartridge casing recovered as evidence, the expert may offer that opinion to a "reasonable degree of ballistic certainty." Where the individual characteristic toolmarks are not so distinctive as to justify such an opinion, a qualified ballistics expert may still offer an opinion based on the class or subclass characteristics that narrows the scope of possible firearms or eliminates a class of possible firearms as the source of the spent projectiles or cartridge casings.
At the defendant's first degree murder trial, a forensic ballistic and firearms identification expert testified that he compared projectiles and cartridge casings from the crime scene with test firings from a handgun believed to be involved in the shootings. The expert testified that, based on the comparisons, he believed that the projectiles and casings found at the scene had come from that particular handgun. The expert noted that, as a matter of science, he could not exclude every other nine millimeter weapon with similar barrel characteristics to the handgun.
On appeal, the defendant argued that the judge erred in admitting the expert's opinion that the handgun found had fired the projectiles and casing recovered at the crime scene. The defendant further argued that the judge erred in denying his request for a Daubert-Lanigan hearing. The defendant also raised various other claims, and after a complete review of the record, the Court concluded that the judge's rulings were either not error or not prejudicial error, and that the evidence was sufficient to sustain the convictions.
The Court thoroughly reviewed the available research on forensic ballistics, including the National Research Council, Strengthening Forensic Science in the United States: A Path Forward (2009) ("NRC report") and The Association of Firearm and Toolmark Examiners "Theory of Identification as it Relates to Toolmarks, 30 AFTE 86 (1998). The Court concluded that a Daubert-Lanigan hearing was not needed. The Court found that the judge had a reasonable basis to conclude that the expert testimony could assist the jury in determining whether the handgun was used in the murders.
The Court found that, in light of its ruling in this case and the findings of the NRC report, guidelines were needed to ensure that expert forensic ballistic testimony assists the jury without misconstruing the science.
The Court acknowledged that "[t]he admission of an opinion to a 'reasonable degree of ballistic certainty' is similar to the manner in which our appellate courts permit other empirically based but subjective opinions to be presented, such as the source of physical injuries or the cause of death." The Court cautioned against using phrases such as "practical impossibility" and "absolute certainty" to avoid giving the jury the impression of greater certainty. The Court also stated that "[t]he phrase 'reasonable degree of scientific certainty' should also be avoided because it suggests that forensic ballistics is a science, where it is clearly as much an art as a science."
"We conclude that, where defense counsel is furnished in discovery with the documentation needed to prepare an effective cross-examination, where a jury are provided with the necessary background regarding the theory and methodology of forensic ballistics, and where an opinion matching a particular firearm to recovered projectiles or cartridge casings is limited to a 'reasonable degree of ballistic certainty,' a jury will be assisted in reaching a verdict by having the benefit of the opinion, as well as the information needed to evaluate the limitations of such an opinion and the weight it deserves."