SJC Weighs in on Admissibility of Expert Testimony Concerning Ballistics Evidence

Earlier this month the Supreme Judicial Court decided COMMONWEALTH vs. PYTOU HEANG 458 Mass. 827 (2011). The case, which was extremely long, revolved around ballistics evidence, both in the admissibility of physical evidence and expert testimony by firearms experts and examiners. It is an excellent case because it outlines the process for admitting ballistics evidence as well as recommended phrases to be used during testimony (and those that should be avoided). The most interesting area of the decision was with the admission and standard of ballistic evidence which I have cut out of the original case and provided here.

The court in deciding stated “The evidence at a criminal trial was more than sufficient to permit a rational jury to conclude beyond a reasonable doubt that the defendant knowingly participated in an armed home robbery and two murders, on theories of both deliberate premeditation and felony-murder, and was knowingly in sole or joint illegal possession of a firearm.

3. Admission of forensic ballistics or firearms identification evidence. The defendant contends that the judge erred by admitting in evidence Trooper Lombard’s expert opinion that the Intratec AB-10 handgun found at 17 Morris Street fired the projectiles and cartridge casings recovered from the scene of the shooting and from Dumas’s body. The defendant further contends that the judge erred by denying his request for a Daubert-Lanigan hearing regarding the admissibility of this opinion. See Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993); Commonwealth v. Lanigan, 419 Mass. 15 (1994). The defendant raised these claims before trial through a motion in limine and again at trial, adequately preserving these issues for appeal.

Forensic ballistics or firearms identification “is the analysis of bullet and cartridge case evidence and the use of that evidence to link specimens to each other and to particular weapons.” National Research Council, Ballistic Imaging 15 (2008) (Ballistic Imaging). Forensic ballistics evidence has long been recognized as admissible in Massachusetts. See, e.g., Commonwealth v. Barbosa, 457 Mass. 773 , 780 (2010); Commonwealth v. Best, 180 Mass. 492 , 495- 496 (1902). At least one source identifies the 1902 case of Commonwealth v. Best, supra, authored by Chief Justice Oliver Wendell Holmes, as being the first in the nation to uphold the admissibility of forensic ballistics evidence in the form of expert testimony and comparison photographs. See 4 D.L. Faigman, M.J. Saks, J. Sanders, & E.K. Cheng, Modern Scientific Evidence: The Law and Science of Expert Testimony 652 (2009); Commonwealth v. Best, supra. Nevertheless, the accuracy and reliability of forensic ballistics evidence have recently been the focus of significant legal and scientific scrutiny. See Ballistic Imaging, supra at 1-87; National Research Council, Strengthening Forensic Science in the United States: A Path Forward 150-155 (2009) (Strengthening Forensic Science). See generally Schwartz, A Systemic Challenge to the Reliability and Admissibility of Firearms and Toolmark Identification, 6 Colum. Sci. & Tech. L. Rev. 1 (2005). Concerns about both the lack of a firm scientific basis for evaluating the reliability of forensic ballistics evidence and the subjective nature of forensic ballistics comparisons have prompted many courts to reexamine the admissibility of such evidence. See United States v. Willock, 696 F. Supp. 2d 536, 546-547, 555-574 (D. Md. 2010); United States v. Taylor, 663 F. Supp. 2d 1170, 1173-1180 (D.N.M. 2009); United States v. Glynn, 578 F. Supp. 2d 567, 568-575 (S.D.N.Y. 2008); United States vs. Diaz, No. CR 05-00167 WHA (N.D. Cal. Feb. 12, 2007); United States v. Natson, 469 F. Supp. 2d 1253, 1259-1262 (M.D. Ga. 2007); United States v. Monteiro, 407 F. Supp. 2d 351, 354-375 (D. Mass. 2006); United States v. Green, 405 F. Supp. 2d 104, 106-124 (D. Mass. 2005); State v. Fleming, 194 Md. App. 76, 97-109 (2010). See also Commonwealth vs. Meeks, SUCR2002-10961, SUCR2003-10575 (Sept. 27, 2006).
The theory underpinning forensic ballistics is that all firearms possess distinctive features that in turn impart distinctive markingsor “toolmarks” onto projectiles and cartridge casings when the weapon is fired. Using a microscope, firearms examiners compare toolmarks found on spent projectiles and cartridge casings to determine whether they were fired from a particular weapon, generally by comparing projectiles and cartridge casings found at the scene of a crime or in an autopsy with ones test-fired from a seized weapon. See Strengthening Forensic Science, supra at 150-151; Ballistic Imaging, supra at 11-86; Theory of Identification as it Relates to Toolmarks, 30 AFTE J. 86, 86-88 (1998) (Theory of Identification I).

The various distinctive features of firearms are known among firearm examiners as “characteristics.” See Strengthening Forensic Science, supra at 152; Ballistic Imaging, supra at 55-64. Firearm characteristics may arise in a variety of ways, including from the design of a firearm, from variations or imperfections in the manufacturing of a firearm, or from wear and tear of a firearm over time. See Ballistic Imaging, supra at 56-61. For example, the boring and rifling of a gun barrel create a series of spiraled ridges inside the barrel that are designed to spin the projectile as it leaves the gun, stabilizing the projectile in flight. These rifling ridges and their corresponding depressions are design features known as “lands” and “grooves,” and they have either a right-handed or left-handed directional “twist.” See id. at 31-32. The lands and grooves in turn impart “striations” or abrasion-type toolmarks onto projectiles as they are pushed out of the barrel, so firearms examiners commonly examine projectiles to determine the number of lands and grooves and the directional twist of the firearm that fired it. See id. at 45- 46.
Gun barrels and rifling ridges may obtain other distinctive characteristics either during the machining process or after a firearm leaves the factory. These other characteristics may arise from the use of a particular machining tool or manufacturing technique, from random manufacturing imperfections, or from use or corrosion of the firearm over time. These characteristics in turn may impart different striated toolmarks onto the surface of a projectile, including on the land and groove engraved areas, which can also be observed by firearms examiners through a microscope. [Note 19] See id. at 31- 32, 45-49, 56-61; Theory of Identification I, supra at 87-88.
Forensic ballistics proponents maintain that a firearms examiner can determine whether two or more projectiles or cartridge casings were fired by the same weapon by comparing various characteristic toolmarks under a microscope. See Strengthening Forensic Science, supra at 150-151; Ballistic Imaging, supra at 55-56. One of the major difficulties in this endeavor is distinguishing so-called “class” and “subclass” characteristics, which create similar toolmarks among a group of weapons, from so-called “individual” characteristics, which create toolmarks that are theoretically unique to each weapon. See Ballistic Imaging, supra at 56-61.
The Association of Firearm and Toolmark Examiners’s Theory of Identification (AFTE Theory of Identification) defines class characteristics as “[m]easurable features of a specimen [resulting from design factors] which indicate a restricted group source.” [Note 20] Theory of Identification, Range of Striae Comparison Reports and Modified Glossary Definitions — An AFTE Criteria for Identification Committee Report, 24 AFTE J. 336, 340 (1992) (Theory of Identification II). See Ballistic Imaging, supra at 57 (defining class characteristics as “general characteristics that separate a group of objects from a universe of diverse objects”). In the context of projectiles, the caliber of the ammunition, the number of lands and grooves, and the directional twist of the rifling are all class characteristics. See Ballistic Imaging, supra at 58. Identification of these class characteristics can narrow down the range of weapons that may have fired a particular projectile, including possibly identifying a single manufacturer and model of weapon, but they cannot be used to pinpoint an individual firearm as the weapon used in a shooting. See id. at 57-58.
Individual characteristics, on the other hand, are “random imperfections or irregularities of tool surfaces [that] are produced incidental to manufacture and/or caused by use, corrosion, or damage [of the tool].” Theory of Identification II, supra at 340. The individual characteristics that leave toolmarks on spent projectiles are microscopic variations of the gun barrel and rifling surfaces caused by random imperfections in the boring and rifling process, or by corrosion or use of the firearm over time. Individual characteristics are theoretically unique to each weapon, and they in turn impart theoretically unique microscopic striated toolmarks onto a projectile’s surface when the weapon is fired. See Strengthening Forensic Science, supra at 150; Ballistic Imaging, supra at 56-58, 61; Theory of Identification II, supra at 339-340.
Subclass characteristics, however, can also result in microscopic striated toolmarks on a projectile’s surface. See Strengthening Forensic Science, supra at 152; Ballistic Imaging, supra at 58-61; Theory of Identification II, supra at 339-340. The AFTE Theory of Identification describes subclass characteristics as features “[p]roduced incidental to manufacture [that] relate to a smaller group source (a subset of the class to which they belong)” and “[c]an arise from a source which changes over time.” Theory of Identification II, supra at 340. Subclass characteristics can be created by the use of a particular machining tool to make a batch of weapons, the use of a specific manufacturing technique, or even a flaw in a manufacturing technique. Ballistic Imaging, supra at 58-61. Similar subclass characteristics can therefore appear in consecutively manufactured weapons or batches of weaponsfrom a particular manufacturer. Because subclass characteristic toolmarks may appear similar to individual characteristic toolmarks under a microscope, see id., the AFTE cautions that examiners must take care to distinguish subclass characteristics from individual characteristics. [Note 21] See Theory of Identification II, supra at 340.
Firearms examiners generally attempt to identify a source weapon by locating individual characteristic toolmark patterns on spent projectiles and cartridge casings recovered at a crime scene and comparing these to projectiles or cartridge casings from test firings of a seized weapon or recovered from other crime scenes. The traditional “pattern matching” approach “relies on art (the cognitive ability to recognize agreement of pattern) and science (supporting the uniqueness of tool surfaces as a means to establishing an identification between a questioned toolmark and the tool that produced it).” Ballistic Imaging, supra at 64, quoting Moran, A Report on the AFTE Theory of Identification and Range of Conclusions for Tool Mark Identification and Resulting Approaches to Casework, 34 AFTE J. 227, 227 (2002). Under the AFTE Theory of Identification, a firearms examiner may offer an opinion that a projectile or cartridge casing was fired from a particular firearm when there is an “[a]greement of a combination of individual characteristics and all discernible class characteristics where the extent of agreement exceeds that which can occur in the comparison of toolmarks made by different tools and is consistent with the agreement demonstrated by toolmarks known to have been produced by the same tool.” Ballistic Imaging, supra at 59. See Theory of Identification I, supra at 86.
A 2008 National Research Council (NRC) report, which contains one of the most comprehensive evaluations of the science underpinning the field of forensic ballistics, accepted as “a minimal baseline standard [that] firearms-related toolmarks are not completely random and volatile; one can find similar marks on bullets and cartridge cases from the same gun.” Ballistic Imaging, supra at 3. But the NRC report also recognized that there are two main problems with the present state of the art of firearms identification.
First, there is little scientific proof supporting the theory that each firearm imparts “unique” individual characteristic toolmarks onto projectiles and cartridge cases. See id. at 3, 70-81. As the NRC report stated: “The validity of the fundamental assumptions of uniqueness and reproducibility of firearms-related toolmarks [have] not yet been fully demonstrated” and a “significant amount of research would be needed to scientifically determine the degree to which firearms-related toolmarks are unique or even to quantitatively characterize the probability of uniqueness.” Id. at 3. In essence, the NRC report concludes that the theory that each firearm has unique features that leave unique toolmarks on all spent projectiles and cartridge casings from that weapon finds support intuitively and anecdotally, but has yet to be proved scientifically. See id.

The second main problem with firearms identification is that the matching of individual characteristics, regardless of the technique used, is highly subjective. See id. at 53-67. The NRC report describes firearms identification as an “inherently subjective” discipline where “an examiner’s assessment of the quality and quantity of resulting toolmarks and the decision of what does or does not constitute a match comes down to a subjective determination based on intuition and experience.” Id. at 55, 82. This finding is echoed in the AFTE Theory of Identification which notes that “identification is subjective in nature, founded on scientific principles and based on the examiner’s training and experience.” Theory of Identification I, supra at 86. The firearms examiner determines what areas on the projectiles or cartridge casings to compare, which toolmarks are meaningful, and how much similarity is sufficient to determine a match. The NRC report also concludes that there is little scientific data demonstrating the reliability of results. See Ballistic Imaging, supra at 54-67.
At the motion hearing, the defense argued that the findings of the NRC report called into question the reliability of forensic ballistics expert testimony and that a Daubert-Lanigan hearing was required to assess the admissibility of the evidence. The judge, who had read the report, gave careful and extensive consideration to the matter, and thoroughly questioned the prosecutor about Trooper Lombard’s proffered testimony. The prosecutor stated that Trooper Lombard would testify to his observations regarding the various kinds of toolmarks on the projectiles and cartridge casings, including the “unique” or individual characteristic markings, and render an opinion of a match “based upon his training and experience and to a degree of scientific certainty.” The judge concluded that, although the NRC report called into question the certainty with which a forensic ballistics match could be declared, the report clearly indicated that similar markings could be found on projectiles and cartridge casing from the same weapon and that firearm examiners could compare these markings, albeit subjectively. Thus, the judge determined that Trooper Lombard’s testimony would be admissible without a Daubert-Lanigan hearing, but he conditioned and limited the scope of the expert’s opinion. The judge ruled that the trooper could testify “to a degree of scientific certainty” that the recovered projectiles were fired by the nine millimeter firearm seized at 17 Morris Street provided he also admitted that he could not exclude the possibility that the projectiles were fired by another nine millimeter firearm.

The forensic ballistics testimony offered by Trooper Lombard, comparing projectiles and cartridge casings recovered as evidence of crimes with those test-fired from a particular firearm, has long been deemed admissible by this court. See, e.g., Commonwealth v. Giacomazza, 311 Mass. 456 , 471 (1942); Commonwealth v. Millen, 289 Mass. 441 , 483, cert. denied, 295 U.S. 765 (1935); Commonwealth v. Best, 180 Mass. 492 , 495-496 (1902). Although the NRC report called into question the exactitude with which a forensic ballistics expert could declare a “match,” there was no evidence before the judge suggesting that firearms examiners could not assist the jury by using their technical expertise to observe and compare toolmarks found on projectiles and cartridge cases. The judge therefore had a reasonable basis to conclude that Trooper Lombard’s expert testimony about his toolmark findings could assist the jury in determining whether any of the weapons recovered at 17 Morris Street was used in the shootings at 58 Cottage Street, and to admit this testimony without a Daubert-Lanigan hearing.

Nor did the judge abuse his discretion in allowing Trooper Lombard to offer his opinion only if he admitted on direct examination that he could not, as a matter of science, exclude every other nine millimeter firearm with six lands and six grooves with a right-hand twist. Given the absence of appellate guidance on this issue, the judge made a reasonable attempt to ensurethat the expert witness fairly informed the jury of his opinion as to a match and the limitations of that opinion.

The defendant further contends, however, that the judge erred in allowing Trooper Lombard, on cross-examination, to testify to his opinion without the limitation required by the judge on direct examination. On direct examination, the trooper conceded that, as a matter of science, he could not exclude every other nine millimeter firearm with six lands and six grooves with a right-hand twist. But on cross-examination, Trooper Lombard twice, without qualification (and without an objection or motion to strike), testified that the projectiles and cartridge cases found at the scene were “fired by that AB-10.” On redirect examination, over objection, the trooper further testified that in his opinion it was a “practical impossibility” that the projectiles or cartridge casings came from any other AB-10 firearm.

We find no prejudicial error here. While the opinions proffered by the trooper on cross-examination and redirect examination lacked the limitations the judge required on direct examination, we conclude that, considering the entirety of the witness’s testimony, the jury were adequately informed of these limitations. The jury were told about the distinction between individual and class characteristics, and that the class characteristics found on the projectiles in this case, six lands and six grooves with a right-hand twist, could match potentially “hundreds” of firearms, including the Intratec AB-10 handgun found at 17 Morris Street. Although the trooper gave his opinion that the projectiles were a “match” to this particular Intratec AB-10 handgun based on the “unique markings” he observed and that he considered it a “practical impossibility” that another weapon could have fired these projectiles, this opinion was adequately tempered by Trooper Lombard’s admissions that he had not compared the projectiles in this case with ones fired from any other Intratec AB-10 firearm and that he could not scientifically exclude the possibility that another weapon with similar class characteristics to an Intratec AB-10 had fired the projectiles.
In light of our ruling today and the findings of the NRC report, we offer the following guidelines to ensure that expertforensic ballistics testimony appropriately assists the jury in finding the facts but does not mislead by reaching beyond its scientific grasp. First, 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. See United States v. Green, 405 F. Supp. 2d 104, 120 (D. Mass. 2005) (absence of notes and photographs by examiner “makes it difficult, if not impossible,” for another expert to reproduce what examiner did); United States vs. Monteiro, Criminal No. 03-10329-PBS (D. Mass. Nov. 28, 2005) (AFTE guidelines require examiners to document identifications by notes, sketches, or photographs, and barring expert forensic ballistics testimony until adequate documentation is provided).

Second, 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. Such background testimony is essential to assist the jury in evaluating any opinion offered by the expert. See Commonwealth v. Lanigan, 419 Mass. 15 , 25 (1994) (purpose of expert testimony is to assist trier of fact); Mass. G. Evid., supra § 702 (same). It is also similar to the type of informative background testimony that is commonly provided before admitting other expert opinions. See, e.g., Commonwealth v. Patterson, 445 Mass. 626 , 628-634 (2005) (expertfingerprint testimony); Commonwealth v. Gaynor, 443 Mass. 245 , 263-270 (2005) (expert DNA testimony).
Third, 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 tool marks found on projectiles and cartridge casings. Where a qualified expert has identified sufficient individual characteristic tool marks 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.” [Note 29] See United States v. Taylor, 663 F. Supp. 2d 1170, 1180 (D.N.M. 2009); United States vs. Diaz, No. CR 05-00167 WHA (N.D. Cal. Feb. 12, 2007); United States v. Monteiro, 407 F. Supp. 2d 351, 372 (D. Mass. 2006). 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 narrow the scope of possible firearms or eliminate a class of possible firearms as the source of the spent projectiles or cartridge casings.

The 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, see, e.g., Commonwealth v. Nardi, 452 Mass. 379 , 383 (2008) (“reasonable degree of medical certainty”),Commonwealth v. DelValle, 443 Mass. 782 , 788 (2005) (same); clinical diagnoses, Commonwealth v. Roberio, 428 Mass. 278 , 280 (1998) (“reasonable degree of scientific certainty”); and psychological opinions, Commonwealth v. Wentworth, 53 Mass. App. Ct. 82 , 86 (2001) (“reasonable degree of psychological certainty”). It is also consistent with the NRC’s recommendation that “[c]onclusions drawn in firearms identification should not be made to imply the presence of a firm statistical basis where none has been demonstrated.” Ballistic Imaging, supra at 82. Cf. Commonwealth v. Mattei, 455 Mass. 840 , 850- 853 (2010) (because it is possible to say to mathematical degrees of statistical certainty that one DNA profile matches another, test results and opinions regarding DNA profile must be accompanied by testimony explaining likelihood of that match occurring in general population). Phrases that could give the jury an impression of greater certainty, such as “practical impossibility” and “absolute certainty,” should be avoided. [Note 31] Cf. Commonwealth v. Gambora, 457 Mass. 715 , 727-728 (2010) (recognizing possibility that it may be error for fingerprint expert to state with absolute certainty that particular latent print matches known print, or that comparisons are error free). The 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. See Ballistic Imaging, supra at 54-56.

We recognize that some courts that have reviewed the research regarding forensic ballistics have come to different conclusions regarding the admissibility of such opinions. See United States v. Glynn, 578 F. Supp. 2d 567, 574-575 (S.D.N.Y. 2008) (permitting ballistics expert to offer opinion only that “firearms match was ‘more likely than not’ “); United States v. Natson, 469 F. Supp. 2d 1253, 1261-1262 (M.D. Ga. 2007) (permitting forensic ballistics expert to offer opinion of match “to a 100% degree of certainty”); United States v. Green, 405 F. Supp. 2d 104, 124 (D. Mass. 2005) (permitting forensic ballistics expert to testify only to expert’s actual observations, and refusing to permit expert to offer opinion that particular firearm was source of recovered shell casings). We recognize that these decisions may have depended to some degree on the quality of the evidence on which the expert’s opinion rested in a particular case, but as a general rule we believe that a middle ground permitting the opinion of a match to a “reasonable degree of ballistic certainty” under these guidelines more fully captures our current understanding of the scientific rigor underpinning forensic ballistics. As the NRC report concludes, toolmarks from firearms are not completely random and volatile, and similar markings can clearly be observed on projectiles and cartridge casings that come from the same fired weapon. See Ballistic Imaging, supra at 3. While the uniqueness of toolmarks has yet to be scientifically determined and while the process by which a firearms examiner declares a “match” remains inherently subjective, “the life of the law [is] experience,” O.W. Holmes, Jr., Common Law 1 (American Bar Association ed. 2009), and that experience has demonstrated that firearms examiners can and consistently do compare such markings and reach opinions that can assist finders of fact. 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.”

Attorney Ronald A. Sellon

About Attorney Ronald A. Sellon

Ronald A. Sellon is a licensed Attorney in the state of Massachusetts and U.S. District Court, Massachusetts as well as a Sergeant with a Municipal Police Department and U.S. military Veteran. Additionally, he has taught Criminal Procedure at the Massachusetts State Police Academy in New Braintree and has written a text on Criminal Procedure for police field training officer programs. He is a graduate of the FBI National Academy, was a 2008 recipient of the Massachusetts Coalition of Police (Mass C.O.P.) Presidents award and holds a Bachelors Degree in Law Enforcement, a Masters Degree in Criminal Justice Administration, and a Juris Doctor Law Degree. Questions related to content material may be directed to RSellon@PoliceLegalPromotions.com
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