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Reference Guide on
Forensic Identification Expertise
P A U L C . G I A N N E L L I , E D WA R D J . I M W I N K E L R I E D ,
AND JOSEPH L. PETERSON
Paul C. Giannelli, L.L.M, is Albert J. Weatherhead III and Richard W. Weatherhead
Professor of Law, and Distinguished University Professor, Case Western Reserve University.
Edward J. Imwinkelried, J.D., is Edward L. Barrett, Jr. Professor of Law and Director of
Trial Advocacy, University of California, Davis.
Joseph L. Peterson, D.Crim., is Professor of Criminal Justice and Criminalistics, California
State University, Los Angeles.
ConTenTs
I. Introduction, 57
II. Development of Forensic Identification Techniques, 58
III. Reappraisal of Forensic Identification Expertise, 60
A. DNA Profiling and Empirical Testing, 60
B. Daubert and Empirical Testing, 62
IV. National Research Council Report on Forensic Science, 64
A. Research, 66
B. Observer Effects, 67
C. Accreditation and Certification, 68
D. Proficiency Testing, 69
E. Standard Terminology, 70
F. Laboratory Reports, 70
V. Specific Techniques, 71
A. Terminology, 71
VI. Fingerprint Evidence, 72
A. The Technique, 73
B. The Empirical Record, 76
1. Proficiency testing, 78
2. The Mayfield case, 79
C. Case Law Development, 81
VII. Handwriting Evidence, 83
A. The Technique, 83
B. The Empirical Record, 85
1. Comparison of experts and laypersons, 86
2. Proficiency studies comparing experts’ performance to chance, 87
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C. Case Law Development, 89
VIII. Firearms Identification Evidence, 91
A. The Technique, 91
1. Firearms, 91
2. Ammunition, 92
3. Class characteristics, 92
4. Subclass characteristics, 93
5. Individual characteristics, 93
6. Consecutive matching striae, 94
7. Cartridge identification, 94
8. Automated identification systems, 95
9. Toolmarks, 96
B. The Empirical Record, 97
C. Case Law Development, 100
IX. Bite Mark Evidence, 103
A. The Technique, 104
1. Theory of uniqueness, 105
2. Methods of comparison, 106
3. ABFO Guidelines, 107
B. The Empirical Record, 108
1. DNA exonerations, 109
C. Case Law Development, 110
1. Specificity of opinion, 111
2. Post-Daubert cases, 112
X. Microscopic Hair Evidence, 112
A. The Technique, 112
B. The Empirical Record, 113
1. Mitochondrial DNA, 116
2. Proficiency testing, 116
3. DNA exonerations, 117
C. Case Law Development, 117
XI. Recurrent Problems, 120
A. Clarity of Testimony, 120
B. Limitations on Testimony, 121
C. Restriction of Final Argument, 124
XII. Procedural Issues, 124
A. Pretrial Discovery, 125
1. Testifying beyond the report, 126
B. Defense Experts, 127
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Reference Guide on Forensic Identification Expertise
I. Introduction
Forensic identification expertise encompasses fingerprint, handwriting, and fire-
arms (“ballistics”), and toolmark comparisons, all of which are used by crime
laboratories to associate or dissociate a suspect with a crime. Shoe and tire prints
also fall within this large pattern evidence domain. These examinations consist of
comparing a known exemplar with evidence collected at a crime scene or from
a suspect. Bite mark analysis can be added to this category, although it developed
within the field of forensic dentistry as an adjunct of dental identification and is
not conducted by crime laboratories. In a broad sense, the category includes trace
evidence such as the analysis of hairs, fibers, soil, glass, and wood. Some forensic
disciplines attempt to individuate and thus attribute physical evidence to a par-
ticular source—a person, object, or location.1 Other techniques are useful because
they narrow possible sources to a discrete category based upon what are known as
“class characteristics” (as opposed to “individual characteristics”). Moreover, some
techniques are valuable because they eliminate possible sources.
Following this introduction, Part II of this guide sketches a brief history of
the development of forensic expertise and crime laboratories. Part III discusses
the impact of the advent of DNA analysis and the Supreme Court’s 1993 Daubert
decision,2 developments that prompted a reappraisal of the trustworthiness of tes-
timony by forensic identification experts. Part IV focuses on the 2009 National
Research Council (NRC) report on forensic science.3 Parts V through X examine
specific identification techniques: (1) fingerprint analysis, (2) questioned document
examination, (3) firearms and toolmark identification, (4) bite mark comparison,
and (5) microscopic hair analysis. Part XI considers recurrent problems, including
the clarity of expert testimony, limitations on its scope, and restrictions on closing
arguments. Part XII addresses procedural issues—pretrial discovery and access to
defense experts.
1. Some forensic scientists believe the word individualization is more accurate than identification.
Paul L. Kirk, The Ontogeny of Criminalistics, 54 J. Crim. L., Criminology & Police Sci. 235, 236 (1963).
The identification of a substance as heroin, for example, does not individuate, whereas a fingerprint
identification does.
2. Daubert v. Merrell Dow Pharms., Inc., 509 U.S. 579 (1993). Daubert is discussed in Margaret
A. Berger, The Admissibility of Expert Testimony, in this manual.
3. National Research Council, Strengthening Forensic Science in the United States: A Path
Forward (2009) [hereinafter NRC Forensic Science Report], available at http://www.nap.edu/catalog.
php?record_id=12589.
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II. Development of Forensic Identification
Techniques
An understanding of the current issues requires some appreciation of the past.
The first reported fingerprint case was decided in 1911.4 This case preceded the
establishment of the first American crime laboratory, which was created in Los
Angeles in 1923.5 The Federal Bureau of Investigation (FBI) laboratory came
online in 1932. At its inception, the FBI laboratory staff included only firearms
identification and fingerprint examination.6 Handwriting comparisons, trace evi-
dence examinations, and serological testing of blood and semen were added later.
When initially established, crime laboratories handled a modest number of cases.
For example, in its first full year of operation, the FBI laboratory processed fewer
than 1000 cases.7
Several sensational cases in these formative years highlighted the value of
forensic identification evidence. The Sacco and Vanzetti trial in 1921 was one
of the earliest cases to rely on firearms identification evidence.8 In 1935, the
extensive use of handwriting comparison testimony9 and wood evidence10 at
the Lindbergh kidnapping trial raised the public consciousness of identification
expertise and solidified its role in the criminal justice system. Crime laboratories
soon sprang up in other large cities such as Chicago and New York.11 The num-
4. People v. Jennings, 96 N.E. 1077 (Ill. 1911).
5. See John I. Thornton, Criminalistics: Past, Present and Future, 11 Lex et Scientia 1, 23 (1975)
(“In 1923, Vollmer served as Chief of Police of the City of Los Angeles for a period of one year.
During that time, a crime laboratory was established at his direction.”).
6. See Federal Bureau of Investigation, U.S. Department of Justice, FBI Laboratory 3 (1981),
available at http://www.ncjrs.gov/App/publications/Abstract.aspx?id=78689.
7. See Anniversary Report, 40 Years of Distinguished Scientific Assistance to Law Enforcement, FBI Law
Enforcement Bull., Nov. 1972, at 4 (“During its first month of service, the FBI Laboratory examiners
handled 20 cases. In its first full year of operation, the volume increased to a total of 963 examinations.
By the next year that figure more than doubled.”).
8. See G. Louis Joughin & Edmund M. Morgan, The Legacy of Sacco & Vanzetti 15 (1948);
see also James E. Starrs, Once More Unto the Breech: The Firearms Evidence in the Sacco and Vanzetti Case
Revisited, Parts I & II, 31 J. Forensic Sci. 630, 1050 (1986).
9. See D. Michael Risinger et al., Exorcism of Ignorance as a Proxy for Rational Knowledge: The
Lessons of Handwriting Identification “Expertise,” 137 U. Pa. L. Rev. 731, 738 (1989).
10. See Shirley A. Graham, Anatomy of the Lindbergh Kidnapping, 42 J. Forensic Sci. 368 (1997).
The kidnapper had used a wooden ladder to reach the second-story window of the child’s bedroom.
Arthur Koehler, a wood technologist and identification expert for the Forest Products Laboratory of the
U.S. Forest Service, traced part of the ladder’s wood from its mill source to a lumberyard near the home
of the accused. Relying on plant anatomical comparisons, he also testified that a piece of the ladder
came from a floorboard in the accused’s attic.
11. See Joseph L. Peterson, The Crime Lab, in Thinking About Police 184, 185 (Carl Klockars
ed., 1983) (“[T]he Chicago Crime Laboratory has the distinction of being one of the oldest in the
country. Soon after, however, many other jurisdictions also built police laboratories in an attempt to
cope with the crimes of violence associated with the 1930s gangster era.”).
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ber of laboratories gradually grew and then skyrocketed. The national campaign
against drug abuse led most crime laboratories to create forensic chemistry units,
and today the analysis of suspected contraband drugs constitutes more than 50%
of the caseload of many laboratories.12 By 2005, the nation’s crime laboratories
were handling approximately 2.7 million cases every year.13 According to a 2005
census, there are now 389 publicly funded crime laboratories in the United States:
210 state or regional laboratories, 84 county laboratories, 62 municipal laborato-
ries, and 33 federal laboratories.14 Currently, these laboratories employ more than
11,900 full-time staff members.15
The establishment of crime laboratories represented a significant reform in
the types of evidence used in criminal trials. Previously, prosecutors had relied
primarily on eyewitness testimony and confessions. The reliability of physical evi-
dence is often superior to that of other types of proof.16 However, the seeds of the
current controversies over forensic identification expertise were sown during this
period. Even though the various techniques became the stock and trade of crime
laboratories, many received their judicial imprimatur without a critical evaluation
of the supporting scientific research.17
This initial lack of scrutiny resulted, in part, from the deference that previ-
ous standards of admissibility accorded the community of specialists in the various
fields of expert testimony. In 1923, the D.C. Circuit adopted the “general accep-
12. J. Peterson & M. Hickman, Bureau of Just. Stat. Bull. (Feb. 2005), NCJ 207205. In most
cases, the forensic chemist simply identifies the unknown as a particular drug. However, in some cases
the chemist attempts to individuate and establish that several drug samples originated from the same
production batch at a particular illegal drug laboratory. See Fabrice Besacier et al., Isotopic Analysis of
13C as a Tool for Comparison and Origin Assignment of Seized Heroin Samples, 42 J. Forensic Sci. 429
(1997); C. Sten et al., Computer Assisted Retrieval of Common-Batch Members in Leukart Amphetamine
Profiling, 38 J. Forensic Sci. 1472 (1993).
13. Matthew R. Durose, Crime Labs Received an Estimated 2.7 Million Cases in 2005, Bureau of Just.
State. Bull. (July 2008) NCJ 222181, available at http://pjs.ojp.usdoj.gov/index.cfm?ty=pbdetail&lid=490
(summarizing statistics compiled by the Justice Department’s Bureau of Justice Statistics).
14. NRC Forensic Science Report, supra note 3, at 58.
15. Id. at 59.
16. For example, in 1927, Justice Frankfurter, then a law professor, sharply critiqued the eye-
witness identifications in the Sacco and Vanzetti case. See Felix Frankfurter, The Case of Sacco and
Vanzetti 30 (1927) (“What is the worth of identification testimony even when uncontradicted? The
identification of strangers is proverbially untrustworthy.”). In 1936, the Supreme Court expressed
grave reservations about the trustworthiness of confessions wrung from a suspect by abusive inter-
rogation techniques. See Brown v. Mississippi, 297 U.S. 278 (1936) (due process violated by beating
a confession out of a suspect).
17. “[F]ingerprints were accepted as an evidentiary tool without a great deal of scrutiny or
skepticism” of their underlying assumptions. Jennifer L. Mnookin, Fingerprint Evidence in an Age of DNA
Profiling, 67 Brook. L. Rev. 13, 17 (2001); see also Risinger et al., supra note 9, at 738 (“Our literature
search for empirical evaluation of handwriting identification turned up one primitive and flawed validity
study from nearly 50 years ago, one 1973 paper that raises the issue of consistency among examiners
but presents only uncontrolled impressionistic and anecdotal information not qualifying as data in any
rigorous sense, and a summary of one study in a 1978 government report. Beyond this, nothing.”).
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tance” test for determining the admissibility of scientific evidence. The case, Frye
v. United States,18 involved a precursor of the modern polygraph. Although the
general acceptance test was limited to mostly polygraph cases for several decades, it
eventually became the majority pre-Daubert standard.19 However, under that test,
scientific testimony is admissible if the underlying theory or technique is generally
accepted by the specialists within the expert’s field. The Frye test did not require
foundational proof of the empirical validity of the technique’s scientific premises.
III. Reappraisal of Forensic Identification
Expertise
The advent of DNA profiling in the late 1980s, quickly followed by the Supreme
Court’s 1993 Daubert decision (rejecting Frye), prompted a reassessment of iden-
tification expertise.20
A. DNA Profiling and Empirical Testing
In many ways, DNA profiling revolutionized the use of expert testimony in crimi-
nal cases.21 Population geneticists, often affiliated with universities, used statistical
techniques to define the extent to which a match of DNA markers individuated
the accused as the possible source of the crime scene sample.22 Typically, the
experts testified to a random-match probability, supporting their opinions by
pointing to extensive empirical testing.
The fallout from the introduction of DNA analysis in criminal trials was sig-
nificant in three ways. First, DNA profiling became the gold standard, regarded
as the most reliable of all forensic techniques.23 NRC issued two reports on the
18. 293 F. 1013 (D.C. Cir. 1923).
19. Frye was cited only five times in published opinions before World War II, mostly in poly-
graph cases. After World War II, it was cited 6 times before 1950, 20 times in the 1950s, and 21 times
in the 1960s. Bert Black et al., Science and the Law in the Wake of Daubert: A New Search for Scientific
Knowledge, 72 Tex. L. Rev. 715, 722 n.30 (1994).
20. See Michael J. Saks & Jonathan J. Koehler, The Coming Paradigm Shift in Forensic Identification
Science, 309 Science 892 (2005).
21. See People v. Wesley, 533 N.Y.S.2d 643, 644 (County Ct. 1988) (calling DNA evidence the
“single greatest advance in the ‘search for truth’ . . . since the advent of cross-examination”).
22. DNA Profiling is examined in detail in David H. Kaye & George Sensabaugh, Reference
Guide on DNA Identification Evidence, in this manual.
23. See Michael Lynch, God’s Signature: DNA Profiling, The New Gold Standard in Forensic Science, 27
Endeavour 2, 93 (2003); Joseph L. Peterson & Anna S. Leggett, The Evolution of Forensic Science: Progress
Amid the Pitfalls, 36 Stetson L. Rev. 621, 654 (2007) (“The scientific integrity and reliability of DNA test-
ing have helped DNA replace fingerprinting and made DNA evidence the new ‘gold standard’ of forensic
evidence”); see also NRC Forensic Science Report, supra note 3, at 40–41 (the ascendancy of DNA).
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subject, emphasizing the importance of certain practices: “No laboratory should
let its results with a new DNA typing method be used in court, unless it has
undergone . . . proficiency testing via blind trials.”24 Commentators soon pointed
out the broader implications of this development:
The increased use of DNA analysis, which has undergone extensive validation,
has thrown into relief the less firmly credentialed status of other forensic science
identification techniques (fingerprints, fiber analysis, hair analysis, ballistics, bite
marks, and tool marks). These have not undergone the type of extensive testing
and verification that is the hallmark of science elsewhere.25
Second, the DNA admissibility battles highlighted the absence of mandatory
regulation of crime laboratories.26 This situation began to change with the pas-
sage of the DNA Identification Act of 1994,27 the first federal statute regulating a
crime laboratory procedure. The Act authorized the creation of a national database
for the DNA profiles of convicted offenders as well as a database for unidentified
profiles from crime scenes: the Combined DNA Index System (CODIS). Bring-
ing CODIS online was a major undertaking, and its successful operation required
an effective quality assurance program. As one government report noted, “the
integrity of the data contained in CODIS is extremely important since the DNA
matches provided by CODIS are frequently a key piece of evidence linking a
suspect to a crime.”28 The statute also established a DNA Advisory Board (DAB)
to assist in promulgating quality assurance standards29 and required proficiency
24. National Research Council, DNA Technology in Forensic Science 55 (1992) [hereinafter
NRC I], available at http://www.nap.edu/catalog.php?record _id=1866. A second report followed.
See National Research Council, The Evaluation of Forensic DNA Evidence (1996), available at http://
www.nap.edu/catalog.php/record_id=5141. The second report also recommended proficiency testing.
Id. at 88 (Recommendation 3.2: “Laboratories should participate regularly in proficiency tests, and the
results should be available for court proceedings.”).
25. Donald Kennedy & Richard A. Merrill, Assessing Forensic Science, 20 Issues in Sci. & Tech. 33,
34 (2003); see also Michael J. Saks & Jonathan J. Koehler, What DNA “Fingerprinting” Can Teach the Law
About the Rest of Forensic Science, 13 Cardozo L. Rev. 361, 372 (1991) (“[F]orensic scientists, like scientists
in all other fields, should subject their claims to methodologically rigorous empirical tests. The results
of these tests should be published and debated.”); Sandy L. Zabell, Fingerprint Evidence, 13 J.L. & Pol’y
143, 143 (2005) (“DNA identification has not only transformed and revolutionized forensic science, it
has also created a new set of standards that have raised expectations for forensic science in general.”).
26. In 1989, Eric Lander, a prominent molecular biologist who became enmeshed in the early
DNA admissibility disputes, wrote: “At present, forensic science is virtually unregulated—with the
paradoxical result that clinical laboratories must meet higher standards to be allowed to diagnose strep
throat than forensic labs must meet to put a defendant on death row.” Eric S. Lander, DNA Finger-
printing on Trial, 339 Nature 501, 505 (1989).
27. 42 U.S.C. § 14131 (2004).
28. Office of Inspector General, U.S. Department of Justice, Audit Report, The Combined
DNA Index System, ii (2001), available at http://www.justice.gov/oig/reports/FBI/a0126/final.pdf.
29. 42 U.S.C. § 14131(b). The legislation contained a “sunset” provision; DAB would expire
after 5 years unless extended by the Director of the FBI. The board was extended for several months
and then ceased to exist. The FBI had established the Technical Working Group on DNA Identifica-
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testing for FBI analysts as well as those in laboratories participating in the national
database or receiving federal funding.30
Third, the use of DNA evidence to exonerate innocent convicts led to a
reexamination of the evidence admitted to secure their original convictions.31
Some studies indicated that, after eyewitness testimony, forensic identification
evidence was one of the most common types of testimony that jurors relied on
at the earlier trials in returning erroneous verdicts.32 These studies suggested that
flawed forensic analyses may have contributed to the convictions.33
B. Daubert and Empirical Testing
The second major development prompting a reappraisal of forensic identification
evidence was the Daubert decision.34 Although there was some uncertainty about
the effect of the decision at the time Daubert was decided, the Court’s subsequent
cases, General Electric Co. v. Joiner35 and Kumho Tire Co. v. Carmichael,36 signaled
tion Methods (TWGDAM) in 1988 to develop standards. TWGDAM functioned under DAB. It was
renamed the Scientific Working Group on DNA Analysis Methods (SWGDAM) in 1999 and replaced
DAB when the latter expired.
30. 42 U.S.C. § 14132(b)(2) (2004) (external proficiency testing for CODIS participation); id.
§ 14133(a)(1)(A) (2004) (FBI examiners). DAB Standard 13 implements this requirement. The Justice
for All Act, enacted in 2004, amended the statute, requiring all DNA labs to be accredited within
2 years “by a nonprofit professional association of persons actively involved in forensic science that is
nationally recognized within the forensic science community” and to “undergo external audits, not
less than once every 2 years, that demonstrate compliance with standards established by the Director
of the Federal Bureau of Investigation.” 42 U.S.C. § 14132(b)(2).
31. See Samuel R. Gross et al., Exonerations in the United States 1989 Through 2003, 95 J. Crim.
L. & Criminology 523, 543 (2005).
32. A study of 200 DNA exonerations found that expert testimony (55%) was the second lead-
ing type of evidence (after eyewitness identifications, 79%) used in the wrongful conviction cases.
Pre-DNA serology of blood and semen evidence was the most commonly used technique (79 cases).
Next came hair evidence (43 cases), soil comparison (5 cases), DNA tests (3 cases), bite mark evidence
(3 cases), fingerprint evidence (2 cases), dog scent (2 cases), spectrographic voice evidence (1 case),
shoe prints (1 case), and fibers (1 case). Brandon L. Garrett, Judging Innocence, 108 Colum. L. Rev. 55,
81 (2008). These data do not necessarily mean that the forensic evidence was improperly used. For
example, serological testing at the time of many of these convictions was simply not as discriminat-
ing as DNA profiling. Consequently, a person could be included using these serological tests but be
excluded by DNA analysis. Yet, some evidence was clearly misused. See also Paul C. Giannelli, Wrong-
ful Convictions and Forensic Science: The Need to Regulate Crime Labs, 86 N.C. L. Rev. 163, 165–70,
172–207 (2007).
33. See Melendez-Diaz v. Massachusetts, 129 S. Ct. 2527, 2537 (2009) (citing Brandon L.
Garrett & Peter J. Neufeld, Invalid Forensic Science Testimony and Wrongful Convictions, 95 Va. L. Rev.
1, 34–84 (2009)). See also Brandon L. Garrett, Convicting the Innocent: Where Criminal Prosecutions
Go Wrong, ch. 4 (2011).
34. Daubert is discussed in detail in Margaret A. Berger, The Admissibility of Expert Testimony,
in this manual.
35. 522 U.S. 136 (1997).
36. 526 U.S. 137 (1999).
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that the Daubert standard may often be more demanding than the traditional Frye
standard.37 Kumho extended the reliability requirement to all types of expert tes-
timony, and in 2000, the Court characterized Daubert as imposing an “exacting”
standard for the admissibility of expert testimony.38
Daubert’s impact in civil cases is well documented.39 Although Daubert’s
effect on criminal litigation has been less pronounced,40 it nonetheless has par-
tially changed the legal landscape. Defense attorneys invoked Daubert as the basis
for mounting attacks on forensic identification evidence, and a number of courts
view the Daubert trilogy as “inviting a reexamination even of ‘generally accepted’
venerable, technical fields.”41 Several courts have held that a forensic technique
is not exempt from Rule 702 scrutiny simply because it previously qualified for
admission under Frye’s general acceptance standard.42
In addition to enunciating a new reliability test, Daubert listed several factors
that trial judges may consider in assessing reliability. The first and most impor-
tant Daubert factor is testability. Citing scientific authorities, the Daubert Court
noted that a hallmark of science is empirical testing. The Court quoted Hempel:
37. See United States v. Horn, 185 F. Supp. 2d 530, 553 (D. Md. 2002) (“Under Daubert, . . .
it was expected that it would be easier to admit evidence that was the product of new science or
technology. In practice, however, it often seems as though the opposite has occurred—application
of Daubert/Kumho Tire analysis results in the exclusion of evidence that might otherwise have been
admitted under Frye.”).
38. Weisgram v. Marley Co., 528 U.S. 440, 455 (2000).
39. See Lloyd Dixon & Brian Gill, Changes in the Standards of Admitting Expert Evidence in
Federal Civil Cases Since the Daubert Decision 25 (2002) (“[S]ince Daubert, judges have examined
the reliability of expert evidence more closely and have found more evidence unreliable as a result.”);
Margaret A. Berger, Upsetting the Balance Between Adverse Interests: The Impact of the Supreme Court’s
Trilogy on Expert Testimony in Toxic Tort Litigation, 64 Law & Contemp. Probs. 289, 290 (2001) (“The
Federal Judicial Center conducted surveys in 1991 and 1998 asking federal judges and attorneys about
expert testimony. In the 1991 survey, seventy-five percent of the judges reported admitting all prof-
fered expert testimony. By 1998, only fifty-nine percent indicated that they admitted all proffered
expert testimony without limitation. Furthermore, sixty-five percent of plaintiff and defendant counsel
stated that judges are less likely to admit some types of expert testimony since Daubert.”).
40. See Jennifer L. Groscup et al., The Effects of Daubert on the Admissibility of Expert Testimony
in State and Federal Criminal Cases, 8 Psychol. Pub. Pol’y & L. 339, 364 (2002) (“[T]he Daubert deci-
sion did not impact on the admission rates of expert testimony at either the trial or the appellate
court levels.”); D. Michael Risinger, Navigating Expert Reliability: Are Criminal Standards of Certainty
Being Left on the Dock? 64 Alb. L. Rev. 99, 149 (2000) (“[T]he heightened standards of dependability
imposed on expertise proffered in civil cases has continued to expand, but . . . expertise proffered by
the prosecution in criminal cases has been largely insulated from any change in pre-Daubert standards
or approach.”).
41. United States v. Hines, 55 F. Supp. 2d 62, 67 (D. Mass. 1999) (handwriting comparison); see
also United States v. Hidalgo, 229 F. Supp. 2d 961, 966 (D. Ariz. 2002) (“Courts are now confronting
challenges to testimony, as here, whose admissibility had long been settled”; discussing handwriting
comparison).
42. See, e.g., United States v. Williams, 506 F.3d 151, 162 (2d Cir. 2007) (“Nor did [Daubert]
‘grandfather’ or protect from Daubert scrutiny evidence that had previously been admitted under
Frye.”); United States v. Starzecpyzel, 880 F. Supp. 1027, 1040 n.14 (S.D.N.Y. 1995).
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“[T]he statements constituting a scientific explanation must be capable of empiri-
cal test,”43 and then Popper: “[T]he criterion of the scientific status of a theory
is its falsifiability, or refutability, or testability.”44 The other factors listed by the
Court are generally complementary. For example, the second factor, peer review
and publication, is a means to verify the results of the testing mentioned in the first
factor; and in turn, verification can lead to general acceptance of the technique
within the broader scientific community.45 These factors serve as circumstantial
evidence that other experts have examined the underlying research and found it
to be sound. Similarly, another factor, an error rate, is derived from testing.
IV. National Research Council Report on
Forensic Science
In 2005, the Science, State, Justice, Commerce, and Related Agencies Appro-
priations Act became law.46 The accompanying Senate report commented that,
“[w]hile a great deal of analysis exists of the requirements of the discipline of
DNA, there exists little or no analysis of the . . . needs of the [forensic] commu-
nity outside of the area of DNA.”47 In the Act, Congress authorized the National
Academy of Sciences (NAS) to conduct a comprehensive study of the current
state of forensic science to develop recommendations. In fall 2006, the Academy
established the Committee on Identifying the Needs of the Forensic Science
Community within NRC to fulfill the task appointed by Congress. In February
2009, NRC released the report Strengthening Forensic Science in the United States:
A Path Forward.48
43. Carl G. Hempel, Philosophy of Natural Science 49 (1966).
44. Karl R. Popper, Conjectures and Refutations: The Growth of Scientific Knowledge 37
(5th ed. 1989).
45. In their amici brief in Daubert, the New England Journal of Medicine and other medical journals
observed:
“Good science” is a commonly accepted term used to describe the scientific community’s system of
quality control which protects the community and those who rely upon it from unsubstantiated scientific
analysis. It mandates that each proposition undergo a rigorous trilogy of publication, replication and
verification before it is relied upon.
Brief for the New England Journal of Medicine, Journal of the American Medical Association, and
Annals of Internal Medicine as Amici Curiae supporting Respondent at *2, Daubert v. Merrell Dow
Pharms., Inc., 509 U.S. 579 (1993) (No. 92-102), 1993 WL 13006387. Peer review’s “role is to pro-
mote the publication of well-conceived articles so that the most important review, the consideration
of the reported results by the scientific community, may occur after publication.” Id. at *3.
46. Pub. L. No. 109-108, 119 Stat. 2290 (2005).
47. S. Rep. No. 109-88, at 46 (2005).
48. NRC Forensic Science Report, supra note 3. The Supreme Court cited the report 3 months
later. Melendez-Diaz v. Massachusetts, 129 S. Ct. 2527 (2009).
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In keeping with its congressional charge, the NRC committee did not address
admissibility issues. The NRC report stated: “No judgment is made about past
convictions and no view is expressed as to whether courts should reassess cases
that already have been tried.”49 When the report was released, the co-chair of the
NRC committee stated:
I want to make it clear that the committee’s report does not mean to offer any
judgments on any cases in the judicial system. The report does not assess past
criminal convictions, nor does it speculate about pending or future cases. And
the report offers no proposals for law reform. That was beyond our charge.
Each case in the criminal justice system must be decided on the record before
the court pursuant to the applicable law, controlling precedent, and governing
rules of evidence. The question whether forensic evidence in a particular case is
admissible under applicable law is not coterminous with the question whether
there are studies confirming the scientific validity and reliability of a forensic
science discipline.50
Yet, in one passage, the report remarked: “Much forensic evidence—including,
for example, bite marks and firearm and toolmark identifications—is introduced in
criminal trials without any meaningful scientific validation, determination of error
rates, or reliability testing to explain the limits of the discipline.”51 Moreover, the
report did discuss a number of forensic techniques and, where relevant, passages
from the report are cited throughout this chapter.
As the NRC report explained, its primary focus is forward-looking—to out-
line an “agenda for progress.”52 The report’s recommendations are wide-ranging,
covering diverse topics such as medical examiner systems,53 interoperability of the
automated fingerprint systems,54 education and training in the forensic sciences,55
codes of ethics,56 and homeland security issues.57 Some recommendations are
49. Id. at 85. The report goes on to state:
The report finds that the existing legal regime—including the rules governing the admissibility of foren-
sic evidence, the applicable standards governing appellate review of trial court decisions, the limitations
of the adversary process, and judges and lawyers who often lack the scientific expertise necessary to
comprehend and evaluate forensic evidence—is inadequate to the task of curing the documented ills of
the forensic science disciplines.
Id.
50. Harry T. Edwards, Co-Chair, Forensic Science Committee, Opening Statement of Press
Conference (Feb. 18, 2009), transcript available at http://www.nationalacademies.org/includes/
OSEdwards.pdf.
51. NRC Forensic Science Report, supra note 3, at 107–08.
52. Id. at xix.
53. Recommendation 10 (urging the replacement of the coroner with medical examiner system
in medicolegal death investigation).
54. Recommendation 11.
55. Recommendation 2.
56. Recommendation 9.
57. Recommendation 12.
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Nonetheless, the courts varied in how far they permitted the expert to go. In some
cases, analysts testified only that the samples matched394 or were similar395 and
thus consistent with the hypothesis that the samples had the same source.396 Other
courts permitted experts to directly opine that the accused was the source of the
crime scene sample.397 However, a 1990 decision held it error to admit testimony
that “it would be improbable that these hairs would have originated from another
individual.”398 In the court’s view, this testimony amounted “effectively, [to] a
positive identification of defendant. . . .”399
On the basis of Gaudette and Keeping research, several courts admitted
opinions in statistical terms (e.g., 1 in 4500 chance of a false match).400 In
contrast, other courts, including a federal court of appeals, reached a contrary
conclusion.401
The most significant post-Daubert challenge to microscopic hair analysis came
in Williamson v. Reynolds,402 a habeas case decided in 1995. There, an expert tes-
tified that, after considering approximately 25 characteristics, he concluded that
the hair samples were “consistent microscopically.” He then elaborated: “In other
words, hairs are not an absolute identification, but they either came from this indi-
vidual or there is—could be another individual somewhere in the world that would
have the same characteristics to their hair.”403 The district court was “unsuccess-
ful in its attempts to locate any indication that expert hair comparison testimony
394. Garland v. Maggio, 717 F.2d 199, 207 n.9 (5th Cir. 1983).
395. United States v. Brady, 595 F.2d 359, 362–63 (6th Cir. 1979).
396. People v. Allen, 115 Cal. Rptr. 839, 842 (Cal. Ct. App. 1974).
397. In the 1986 Mississippi prosecution of Randy Bevill for murder, the expert testified that
“there was a transfer of hair from the Defendant to the body of” the victim. Clive A. Stafford Smith &
Patrick D. Goodman, Forensic Hair Comparison Analysis: Nineteenth Century Science or Twentieth Century
Snake Oil? 27 Colum. Hum. Rts. L. Rev. 227, 273 (1996).
398. State v. Faircloth, 394 S.E.2d 198, 202–03 (N.C. Ct. App. 1990).
399. Id. at 202.
400. United States v. Jefferson, 17 M.J. 728, 731 (N.M.C.M.R. 1983); People v. DiGiacomo,
388 N.E.2d 1281, 1283 (Ill. App. Ct. 1979); see also United States ex rel. DiGiacomo v. Franzen, 680
F.2d 515, 516 (7th Cir. 1982) (During its deliberations, the jury submitted the following question to
the judge: “Has it been established by sampling of hair specimens that the defendant was positively
proven to have been in the automobile?”).
401. United States v. Massey, 594 F.2d 676, 679–80 (8th Cir. 1979) (the expert testified that he
“had microscopically examined 2,000 cases and in only one or two cases was he ever unable to make
identification”; the expert cited a study for the proposition that there was a 1 in 4500 chance of a
random match; the expert added that “there was only ‘one chance in a 1,000’ that hair comparisons
could be in error”); State v. Carlson, 267 N.W.2d 170, 176 (Minn. 1978).
402. 904 F. Supp. 1529, 1554 (E.D. Okla. 1995), rev’d on this issue sub nom. Williamson v. Ward,
110 F.3d 1508, 1523 (10th Cir. 1997). The district court noted that the “expert did not explain which
of the ‘approximately’ 25 characteristics were consistent, any standards for determining whether the
samples were consistent, how many persons could be expected to share this same combination of
characteristics, or how he arrived at his conclusions.” Id. at 1554.
403. Id. (emphasis added).
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meets any of the requirements of Daubert.”404 Finally, the prosecutor in closing
argument declared, “There’s a match.”405 Even the state court had misinterpreted
the evidence, writing that the “hair evidence placed [petitioner] at the decedent’s
apartment.”406 Although the Tenth Circuit did not fault the district judge’s read-
ing of the empirical record relating to hair analysis and ultimately upheld habeas
relief, that court reversed the district judge on this issue. The Tenth Circuit ruled
that the district had committed legal error because the due process (fundamental
fairness), not the more stringent Daubert (reliability), standard controls evidentiary
issues in habeas corpus proceedings.407 Before retrial, the defendant was exoner-
ated by exculpatory DNA evidence.408
Post-Daubert, many cases have continued to admit testimony about micro-
scopic hair analysis.409 In 1999, one state court judicially noticed the reliability
of hair evidence,410 implicitly finding this evidence to be not only admissible
but also based on a technique of indisputable validity.411 In contrast, a Missouri
court reasoned that, without the benefit of population frequency data, an expert
overreached in opining to “a reasonable degree of certainty that the unidentified
hairs were in fact from” the defendant.412 The NRC report commented that
there appears to be growing judicial support for the view that “testimony linking
microscopic hair analysis with particular defendants is highly unreliable.”413
404. Id. at 1558. The court also observed: “Although the hair expert may have followed proce-
dures accepted in the community of hair experts, the human hair comparison results in this case were,
nonetheless, scientifically unreliable.” Id.
405. Id. at 1557.
406. Id. (quoting Williamson v. State, 812 P.2d 384, 387 (Okla. Crim. 1991)).
407. Williamson v. Ward, 110 F.3d 1508, 1523 (10th Cir. 1997).
408. Scheck et al., supra note 388, at 146 (hair evidence was shown to be “patently unreliable.”);
see also John Grisham, The Innocent Man (2006) (examining the Williamson case).
409. E.g., State v. Fukusaku, 946 P.2d 32, 44 (Haw. 1997) (“Because the scientific principles
and procedures underlying hair and fiber evidence are well-established and of proven reliability, the
evidence in the present case can be treated as ‘technical knowledge.’ Thus, an independent reliability
determination was unnecessary.”); McGrew v. State, 682 N.E.2d 1289, 1292 (Ind. 1997) (concluding
that hair comparison is “more a ‘matter of observation by persons with specialized knowledge’ than
‘a matter of scientific principles’”); see also NRC Forensic Science Report, supra note 3, at 161 n.88
(citing State v. West, 877 A.2d 787 (Conn. 2005), and Bookins v. State, 922 A.2d 389 (Del. Super.
Ct. 2007)).
410. See Johnson v. Commonwealth, 12 S.W.3d 258, 262 (Ky. 1999).
411. See Fed. R. Evid. 201(b); Daubert, 509 U.S. at 593 n.11 (“[T]heories that are so firmly
established as to have attained the status of scientific law, such as the laws of thermodynamics, properly
are subject to judicial notice under Federal Rule [of] Evidence 201.”).
412. Butler v. State, 108 S.W.3d 18, 21–22 (Mo. Ct. App. 2003).
413. NRC Forensic Science Report, supra note 3, at 161.
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XI. Recurrent Problems
The discussions of specific techniques in this chapter, as well as the 2009 NRC
report, reveal several recurrent problems in the presentation of testimony about
forensic expertise.
A. Clarity of Testimony
As noted earlier, the report voiced concern about the use of terms such as “match,”
“consistent with,” “identical,” “similar in all respects tested,” and “cannot be
excluded as the source of.” These terms can have “a profound effect on how the trier
of fact in a criminal or civil matter perceives and evaluates scientific evidence.”414
The comparative bullet lead cases are illustrative of this point.415 The tech-
nique was used when conventional firearms identification was not possible because
the recovered bullet was so deformed that the striations were destroyed. In the
bullet lead cases, the phrasing of the experts’ opinions varied widely. In some,
experts testified only to the limited opinion that two exhibits were “analytically
indistinguishable.”416 In other cases, examiners concluded that samples could have
come from the same “source” or “batch.”417 In still others, they stated that the
samples came from the same source.418 In several cases, the experts went even
further and identified a particular “box” of ammunition (usually 50 loaded car-
tridges, sometimes 20) as the source of the bullet recovered at the crime scene.
For example, experts opined that two specimens:
• Could have come from the same box.419
• Could have come from the same box or a box manufactured on the same
day.420
414. Id. at 21.
415. The technique compared trace chemicals found in bullets at crime scenes with ammunition
found in the possession of a suspect. It was used when firearms (“ballistics”) identification could not be
employed. FBI experts used various analytical techniques (first, neutron activation analysis, and then
inductively coupled plasma-atomic emission spectrometry) to determine the concentrations of seven
elements—arsenic, antimony, tin, copper, bismuth, silver, and cadmium—in the bullet lead alloy of
both the crime-scene and suspect’s bullets. Statistical tests were then used to compare the elements in
each bullet and determine whether the fragments and suspect’s bullets were “analytically indistinguish-
able” for each of the elemental concentration means.
416. See Wilkerson v. State, 776 A.2d 685, 689 (Md. Ct. Spec. App. 2001).
417. See State v. Krummacher, 523 P.2d 1009, 1012–13 (Or. 1974) (en banc).
418. See United States v. Davis, 103 F.3d 660, 673–74 (8th Cir. 1996); People v. Lane, 628
N.E.2d 682, 689–90 (Ill. App. Ct. 1993).
419. See State v. Jones, 425 N.E.2d 128, 131 (Ind. 1981); State v. Strain, 885 P.2d 810, 817
(Utah Ct. App. 1994).
420. See State v. Grube, 883 P.2d 1069, 1078 (Idaho 1994); People v. Johnson, 499 N.E.2d
1355, 1366 (Ill. 1986); Earhart v. State, 823 S.W.2d 607, 614 (Tex. Crim. App. 1991) (en banc) (“He
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• Were consistent with their having come from the same box of ammunition.421
• Probably came from the same box.422
• Must have come from the same box or from another box that would have
been made by the same company on the same day.423
Moreover, these inconsistent statements were not supported by empiri-
cal research. According to a 2004 NRC report, the number of bullets that can
be produced from an “analytically indistinguishable” melt “can range from the
equivalent of as few as 12,000 to as many as 35 million 40 grain, .22 caliber long-
rifle bullets.”424 Consequently, according to the 2004 NRC report, the “available
data do not support any statement that a crime bullet came from a particular box
of ammunition. [R]eferences to ‘boxes’ of ammunition in any form should be
excluded as misleading under Federal Rule of Evidence 403.”425
B. Limitations on Testimony
Some courts have limited the scope of the testimony, permitting expert testimony
about the similarities and dissimilarities between exemplars but not the specific
conclusion that the defendant was the author (“common authorship” opinion).426
Although the courts have used this approach most frequently in questioned docu-
later modified that statement to acknowledge that analytically indistinguishable bullets which do not
come from the same box most likely would have been manufactured at the same place on or about
the same day; that is, in the same batch.”), vacated, 509 U.S. 917 (1993).
421. See State v. Reynolds, 297 S.E.2d 532, 534 (N.C. 1982).
422. See Bryan v. State, 935 P.2d 338, 360 (Okla. Crim. App. 1997).
423. See Davis, 103 F.3d at 666–67 (“An expert testified that such a finding is rare and that the
bullets must have come from the same box or from another box that would have been made by the
same company on the same day.”); Commonwealth v. Daye, 587 N.E.2d 194, 207 (Mass. 1992); State
v. King, 546 S.E.2d 575, 584 (N.C. 2001) (Kathleen Lundy “opined that, based on her lead analysis,
the bullets she examined either came from the same box of cartridges or came from different boxes
of the same caliber, manufactured at the same time.”).
424. National Research Council, Forensic Analysis: Weighing Bullet Lead Evidence 6 (2004),
[hereinafter NRC Bullet Lead Evidence], available at http://www.nap.edu/catalog.php?record_id=10924.
425. Id.
426. See United States v. Oskowitz, 294 F. Supp. 2d 379, 384 (E.D.N.Y. 2003) (“Many other
district courts have similarly permitted a handwriting expert to analyze a writing sample for the jury
without permitting the expert to offer an opinion on the ultimate question of authorship.”); United
States v. Rutherford, 104 F. Supp. 2d 1190, 1194 (D. Neb. 2000) (“[T]he Court concludes that FDE
Rauscher’s testimony meets the requirements of Rule 702 to the extent that he limits his testimony
to identifying and explaining the similarities and dissimilarities between the known exemplars and
the questioned documents. FDE Rauscher is precluded from rendering any ultimate conclusions on
authorship of the questioned documents and is similarly precluded from testifying to the degree of
confidence or certainty on which his opinions are based.”); United States v. Hines, 55 F. Supp. 2d 62,
69 (D. Mass. 1999) (expert testimony concerning the general similarities and differences between a
defendant’s handwriting exemplar and a stick-up note was admissible but not the specific conclusion
that the defendant was the author).
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ment cases, they have sometimes applied the same approach to other types of
forensic expertise such as firearms examination as well.427
The NRC report criticized “exaggerated”428 testimony such as claims of per-
fect accuracy,429 infallibility,430 or a zero error rate.431 Several courts have barred
excessive expert claims for lack of empirical support. For example, in United States
v. Mitchell,432 the court commented: “Testimony at the Daubert hearing indicated
that some latent fingerprint examiners insist that there is no error rate associated
with their activities. . . . This would be out-of-place under Rule 702.”433 Simi-
larly, in a firearms identification case, one court noted that
during the testimony at the hearing, the examiners testified to the effect that they
could be 100 percent sure of a match. Because an examiner’s bottom line opinion
as to an identification is largely a subjective one, there is no reliable statistical or
scientific methodology which will currently permit the expert to testify that it is a
‘match’ to an absolute certainty, or to an arbitrary degree of statistical certainty.434
Other courts have excluded the use of terms such as “science” or “scientific,”
because of the risk that jurors may bestow the aura of the infallibility of science on
the testimony.435
In particular, some courts are troubled by the use of the expression “reason-
able scientific certainty” by some forensic experts. The term “reasonable scientific
certainty” is problematic. Although it is used frequently in cases, its legal meaning
is ambiguous.436 Sometimes it is used in lieu of a confidence statement (i.e., “high
degree of certainty”), in which case the expert could altogether avoid the term
and directly testify how confident he or she is in the opinion.
In other cases, courts have interpreted reasonable scientific certainty to mean
that the expert must testify that a sample probably came from the defendant and not
427. United States v. Green, 405 F. Supp. 2d 104, 124 (D. Mass. 2005).
428. NRC Forensic Science Report, supra note 3, at 4.
429. Id. at 47.
430. Id. at 104.
431. Id. at 142–43.
432. 365 F.3d 215 (3d Cir. 2004).
433. Id. at 246.
434. United States v. Monteiro, 407 F. Supp. 2d 351, 372 (D. Mass. 2006).
435. United States v. Starzecpyzel, 880 F. Supp. 1027, 1038 (S.D.N.Y. 1995).
436. James E. Hullverson, Reasonable Degree of Medical Certainty: A Tort et a Travers, 31 St. Louis
U. L.J. 577, 582 (1987) (“[T]here is nevertheless an undercurrent that the expert in federal court
express some basis for both the confidence with which his conclusion is formed, and the probability
that his conclusion is accurate.”); Edward J. Imwinkelried & Robert G. Scofield, The Recognition of
an Accused’s Constitutional Right to Introduce Expert Testimony Attacking the Weight of Prosecution Science
Evidence: The Antidote for the Supreme Court’s Mistaken Assumption in California v. Trombetta, 33 Ariz.
L. Rev. 59, 69 (1991) (“Many courts continue to exclude opinions which fall short of expressing a
probability or certainty. . . . These opinions have been excluded in jurisdictions which have adopted
the Federal Rules of Evidence.”).
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that it possibly came from the defendant.437 However, experts frequently testify that
two samples “could have come from the same source.” Such testimony meets the
relevancy standard of Federal Rule 401, and there is no requirement in Article VII
of the Federal Rules that an expert’s opinion be expressed in terms of “prob-
abilities.” Thus, in United States v. Cyphers438 the expert testified that hair samples
found on items used in a robbery “could have come” from the defendants.439 The
defendants argued that the testimony was inadmissible because the expert did not
express his opinion in terms of reasonable scientific certainty. The court wrote:
“There is no such requirement.”440
In Burke v. Town of Walpole,441 a bite mark identification case, the court of
appeals had to interpret the term as used in an arrest warrant:
[W]e must assume that the magistrate who issued the arrest warrant assigned no
more than the commonly accepted meaning among lawyers and judges to the
term “reasonable degree of scientific certainty”—“a standard requiring a showing
that the injury was more likely than not caused by a particular stimulus, based on
the general consensus of recognized [scientific] thought.” Black’s Law Dictionary
1294 (8th ed. 2004) (defining “reasonable medical probability,” or “reasonable
medical certainty,” as used in tort actions). That standard, of course, is fully
consistent with the probable cause standard.442
The case involved the guidelines adopted by ABFO that recognized several levels
of certainty (“reasonable medical certainty,” “high degree of certainty,” and
“virtual certainty”). The guidelines described “reasonable medical certainty” as
“convey[ing] the connotation of virtual certainty or beyond reasonable doubt.”443
This is not the way that some courts use the term.
437. State v. Holt, 246 N.E.2d 365, 368 (Ohio 1969). The expert testified, based on neutron
activation analysis, that two hair samples were “similar and . . . likely to be from the same source”
(emphasis in original).
438. 553 F.2d 1064 (7th Cir. 1977).
439. Id. at 1072; see also United States v. Davis, 44 M.J. 13, 16 (C.A.A.F. 1996) (“Evidence was
also admitted that appellant owned sneakers which ‘could have’ made these prints.”).
440. Cyphers, 553 F.2d at 1072; see also United States v. Oaxaca, 569 F.2d 518, 526 (9th Cir.
1978) (expert’s opinion regarding hair comparison admissible even though expert was less than certain);
United States v. Spencer, 439 F.2d 1047, 1049 (2d Cir. 1971) (expert’s opinion regarding handwriting
comparison admissible even though expert did not make a positive identification); United States v.
Longfellow, 406 F.2d 415, 416 (4th Cir. 1969) (expert’s opinion regarding paint comparison admis-
sible, even though expert did not make a positive identification); State v. Boyer, 406 So. 2d 143, 148
(La. 1981) (reasonable scientific certainty not required where expert testifies concerning the presence
of gunshot residue based on neutron activation analysis).
441. 405 F.3d 66 (1st Cir. 2005).
442. Id. at 91.
443. Id. at 91 n.30 (emphasis omitted).
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Moreover, the term may be problematic for a different reason—misleading
the jury. One court ruled that the term “reasonable scientific certainty” could not
be used because of the subjective nature of the opinion.444
C. Restriction of Final Argument
In a number of cases, in summation counsel has overstated the content of the
expert testimony. In People v. Linscott,445 for example, “the prosecutor argued
that hairs found in the victim’s apartment and on the victim’s body were in fact
defendant’s hairs.”446 Reversing, the Illinois Supreme Court wrote: “With these
statements, the prosecutor improperly argued that the hairs removed from the
victim’s apartment were conclusively identified as coming from defendant’s head
and pubic region. There simply was no testimony at trial to support these state-
ments. In fact, [the prosecution experts] and the defense hair expert . . . testified
that no such identification was possible.”447 DNA testing exculpated Linscott.448
Trial judges can police the attorneys’ descriptions of the testimony during closing
argument as well as the content of expert testimony presented.
XII. Procedural Issues
The Daubert standard operates in a procedural setting, not a vacuum. In Daubert,
the Supreme Court noted that “[v]igorous cross-examination, presentation of con-
trary evidence, and careful instruction on the burden of proof are the traditional
and appropriate means of attacking shaky but admissible evidence.”449 Adversarial
testing presupposes advance notice of the content of the expert’s testimony and
access to comparable expertise to evaluate that testimony. This section discusses
some of the procedural mechanisms that trial judges may use to assure that jurors
properly evaluate any expert testimony by forensic identification experts.
444. United States v. Glynn, 578 F. Supp. 2d 567, 568–75 (S.D.N.Y. 2008) (firearms identifica-
tion case).
445. 566 N.E.2d 1355 (Ill. 1991).
446. Id. at 1358.
447. Id. at 1359.
448. See Connors et al., supra note 387, at 65 (“The State’s expert on the hair examination
testified that only 1 in 4,500 persons would have consistent hairs when tested for 40 different charac-
teristics. He only tested between 8 and 12 characteristics, however, and could not remember which
ones. The appellate court ruled on July 29, 1987, that his testimony, coupled with the prosecution’s
use of it at closing arguments, constituted denial of a fair trial.”) (citation omitted).
449. 509 U.S. at 596 (citing Rock v. Arkansas, 483 U.S. 44, 61 (1987)).
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A. Pretrial Discovery
Judges can monitor discovery in scientific evidence cases to ensure that disclosure
is sufficiently comprehensive.450 Federal Rule 16 requires discovery of laboratory
reports451 and a summary of the expert’s opinion.452 The efficacy of these provi-
sions depends on the content of the reports and the summary. The Journal of Forensic
Sciences, the official publication of the American Academy of Forensic Sciences,
published a symposium on the ethical responsibilities of forensic scientists in 1989.
One symposium article described a number of unacceptable laboratory reporting
practices, including (1) “preparation of reports containing minimal information in
order not to give the ‘other side’ ammunition for cross-examination,” (2) “report-
ing of findings without an interpretation on the assumption that if an interpretation
is required it can be provided from the witness box,” and (3) “[o]mitting some
significant point from a report to trap an unsuspecting cross-examiner.”453
NRC has recommended extensive discovery in DNA cases: “All data and
laboratory records generated by analysis of DNA samples should be made freely
available to all parties. Such access is essential for evaluating the analysis.”454 The
NRC report on bullet lead contained similar comments about the need for a
thorough report in bullet lead cases:
The conclusions in laboratory reports should be expanded to include the limita-
tions of compositional analysis of bullet lead evidence. In particular, a further
450. See Fed. R. Crim. P. 16 (1975) advisory committee’s note (“[I]t is difficult to test expert
testimony at trial without advance notice and preparation.”), reprinted in 62 F.R.D. 271, 312 (1974);
Paul C. Giannelli, Criminal Discovery, Scientific Evidence, and DNA, 44 Vand. L. Rev. 791 (1991). “Early
disclosure can have the following benefits: [1] Avoiding surprise and unnecessary delay. [2] Identify-
ing the need for defense expert services. [3] Facilitating exoneration of the innocent and encouraging
plea negotiations if DNA evidence confirms guilt.” National Institute of Justice, President’s DNA
Initiative: Principles of Forensic DNA for Officers of the Court (2005), available at http://www.dna.
gov/training/otc.
451. Fed. R. Crim. P. 16(a)(1)(F).
452. Id. 16(a)(1)(G).
453. Douglas M. Lucas, The Ethical Responsibilities of the Forensic Scientist: Exploring the Limits, 34
J. Forensic Sci. 719, 724 (1989). Lucas was the Director of The Centre of Forensic Sciences, Ministry
of the Solicitor General, Toronto, Ontario.
454. National Research Council, DNA Technology in Forensic Science 146 (1992) (“The
prosecutor has a strong responsibility to reveal fully to defense counsel and experts retained by the
defendant all material that might be necessary in evaluating the evidence.”); see also id. at 105 (“Case
records—such as notes, worksheets, autoradiographs, and population databanks—and other data or
records that support examiners’ conclusions are prepared, retained by the laboratory, and made avail-
able for inspection on court order after review of the reasonableness of a request.”); National Research
Council, The Evaluation of Forensic DNA Evidence 167–69 (1996) (“Certainly, there are no strictly
scientific justifications for withholding information in the discovery process, and in Chapter 3 we
discussed the importance of full, written documentation of all aspects of DNA laboratory operations.
Such documentation would facilitate technical review of laboratory work, both within the laboratory
and by outside experts. . . . Our recommendations that all aspects of DNA testing be fully documented
is most valuable when this documentation is discoverable in advance of trial.”).
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explanatory comment should accompany the laboratory conclusions to portray
the limitations of the evidence. Moreover, a section of the laboratory report
translating the technical conclusions into language that a jury could understand
would greatly facilitate the proper use of this evidence in the criminal justice
system. Finally, measurement data (means and standard deviations) for all of the
crime scene bullets and those deemed to match should be included.455
As noted earlier, the recent NRC report made similar comments:
Some reports contain only identifying and agency information, a brief descrip-
tion of the evidence being submitted, a brief description of the types of analysis
requested, and a short statement of the results (e.g., “the greenish, brown plant
material in item #1 was identified as marijuana”), and they include no mention
of methods or any discussion of measurement uncertainties.456
Melendez-Diaz v. Massachusetts457 illustrates the problem. The laboratory
report in that case “contained only the bare-bones statement that ‘[t]he substance
was found to contain: Cocaine.’ At the time of trial, petitioner did not know
what tests the analysts performed, whether those tests were routine, and whether
interpreting their results required the exercise of judgment or the use of skills that
the analysts may not have possessed.”458
1. Testifying beyond the report
Experts should generally not be allowed to testify beyond the scope of the report
without issuing a supplemental report. Troedel v. Wainwright,459 a capital murder
case, illustrates the problem. In that case, a report of a gunshot residue test based
on neutron activation analysis stated the opinion that swabs “from the hands of
Troedel and Hawkins contained antimony and barium in amounts typically found
on the hands of a person who has discharged a firearm or has had his hands in close
proximity to a discharging firearm.”460 An expert testified consistently with this
report at Hawkins’ trial but embellished his testimony at Troedel’s trial by adding
the more inculpatory opinion that “Troedel had fired the murder weapon.”461 In
contrast, at a deposition during federal habeas proceedings, the same expert testi-
fied that “he could not, from the results of his tests, determine or say to a scientific
certainty who had fired the murder weapon” and the “amount of barium and
antimony on the hands of Troedel and Hawkins were basically insignificant.”462
The district court found the trial testimony, “at the very least,” misleading and
455. See NRC Bullet Lead Evidence, supra note 424, at 110–11.
456. NRC Forensic Science Report, supra note 3, at 21.
457. 129 S. Ct. 2527 (2009).
458. Id. at 2537.
459. 667 F. Supp. 1456 (S.D. Fla. 1986), aff’d, 828 F.2d 670 (11th Cir. 1987).
460. Id. at 1458.
461. Id.
462. Id. at 1459.
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granted relief.463 The expert claimed that the prosecutor had “pushed” him to
embellish his testimony, a claim the prosecutor substantiated.464
B. Defense Experts
In appropriate cases, trial judges can provide the opposition with access to expert
resources. Defense experts are often important in cases involving forensic iden-
tification expertise. Counsel will frequently need expert guidance to determine
whether a research study is methodologically sound and, if so, whether the data
adequately support the specific opinion proffered, and the role, if any, that subjec-
tive judgment played in forming the opinion.
The NAS 1992 DNA report stressed that experts are necessary for an ade-
quate defense in many cases: “Defense counsel must have access to adequate
expert assistance, even when the admissibility of the results of analytical techniques
is not in question because there is still a need to review the quality of the labora-
tory work and the interpretation of results.”465 According to the President’s DNA
Initiative, “[e]ven if DNA evidence is admitted, there still may be disagreement
about its interpretation—what do the DNA results mean in a particular case?”466
The need for defense experts is not limited to cases involving DNA evidence.
In Ake v. Oklahoma,467 the Supreme Court recognized a due process right to a
defense expert under certain circumstances.468 In federal trials, the Criminal Justice
Act of 1964469 provides for expert assistance for indigent defendants.
463. “[T]he Court concludes that the opinion Troedel had fired the weapon was known by the
prosecution not to be based on the results of the neutron activation analysis tests, or on any scientific
certainty or even probability. Thus, the subject testimony was not only misleading, but also was used
by the State knowing it to be misleading.” Id. at 1459–60.
464. Id. at 1459 (“[A]s Mr. Riley candidly admitted in his deposition, he was ‘pushed’ further
in his analysis at Troedel’s trial than at Hawkins’ trial. . . . [At the] evidentiary hearing held before
this Court, one of the prosecutors testified that, at Troedel’s trial, after Mr. Riley had rendered his
opinion which was contained in his written report, the prosecutor pushed to ‘see if more could have
been gotten out of this witness.’”).
465. NRC I, supra note 24, at 149 (“Because of the potential power of DNA evidence, authori-
ties must make funds available to pay for expert witnesses. . . .”).
466. President’s DNA Initiative, supra note 450.
467. 470 U.S. 68 (1985); see Paul C. Giannelli, Ake v. Oklahoma: The Right to Expert Assistance
in a Post-Daubert, Post-DNA World, 89 Cornell L. Rev. 1305 (2004).
468. Ake, 470 U.S. at 74.
469. 18 U.S.C. § 3006(A).
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