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Commonwealth v. Pytou Heang, 942 N.E.2d 927 (Mass. 2011)

Case (cite)
Commonwealth v. Pytou Heang, 942 N.E.2d 927 (Mass. 2011)
Type of proceeding
Type of claim
Type of claim (second claim)
Expert evidence ruling reversing or affirming on appeal:
What was the ruling?
Correct to Admit
Type of evidence at issue:
Firearms identification
Defense or Prosecution Expert
Name of expert(s) who were the subject of the ruling
Trooper Brian Lombard
Summary of reasons for ruling
Because the trial judge appropriatey required that the testimony be limited, and because firearms identification testimonies have been consistently admitted in MA without evidentiary hearing, the trial court did not abuse its discretion admitting the ballistics testimony.
The jurisdiction’s standard for expert admissibility at the time – list all that apply: (Frye), (Daubert), (Post-2000 Rule 702), (Other)
Second standard
Did lower court hold a hearing
Names of prosecution expert(s) two testified at hearing
Trooper Lombard
Names of defense expert(s) who testified at hearing (or None).
Discussion of 2009 NAS Report (NAS2009)
Discussion of 2016 PCAST report (PCAST)
Discussion of error rates / reliability
Frye Ruling
Limiting testimony ruling
Language imposed by court to limit testimony
Ruling based in prior precedent / judicial notice
Daubert ruling emphasizing – which factors – (list 1-5)
Ruling on qualifications of expert
Ruling on 702(a) – the expert will help / assist the jury
Ruling on 702(b) – the testimony is based on sufficient facts or data
Ruling on 702(c) – the testimony is the product of reliable principles and methods
Ruling on 702(d) – reliable application of principles and methods to the facts of the case


1. Footnote 26: “At trial, after hearing most of [the expert’s] direct testimony . . . the judge . . . required the prosecutor to ask whetehr [the expert] could ‘exclude all other nine millimeter weapons that have six lands and six grooves with a right-hand twist . . . [a]s a matter of science.'” 2. In MA, “an evidentiary Daubert-Lanigan hearing is generally not required when [the courts] have previously admitted expert testimony of the same type . . . whether the appropriate methodology has been followed, or whether the quality of the evidence is sufficient to permit an opinion.” 3. Defendant contended that the judge erred in allowing the expert, on cross-examination, to tesity without the limitation required by the judge on direct examination (expert used the language like “virtually impossible” on cross-examination). The appellate court found no prejudicial error, “considerding the entirety of the witness’s testimony, the jury were adequately informed of the limitations.” 3. “In light of our ruling today and the findings of the NRC report, we offer the following guidelines to ensure that expert forensic 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 . . . 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. Second, before an opinion is offered at trial, a forensic ballistics expert should explain to the jury the thoeries and methodologies underlying the field of forensic ballistics. . . . Third, in the absence of special circumstances casting doubt on the reliability of an opinion . . . the expert may offer that opinion to a ‘reasonable degree of ballistic certainty.'” 4. “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. . . . The phrase, ‘reasonable degree of scientific certainty’ should be avoided because it suggests that forensic ballistics is a science, where it is clearly as much an art as a science.”




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 ensure *846 that the expert witness fairly informed the jury of his opinion as to a match and the limitations of that opinion.