Reprinted from the Criminal Law Bulletin with the permission of West Group.

Further Reproduction of any kind is prohibited.

[Some Typographic Corrections from Printed Text]

 

“All we want you to do is confirm what we already know”

A Daubert Challenge to Firearms Identifications

by Lisa J. Steele*

 

Firearms identification has been an accepted form of criminal evidence since the early 20th century. Firearms examiners routinely testify that a particular firearm fired a particular bullet or cartridge, or that a number of bullets or cartridges were fired by the same, or different, unrecovered firearms. Generally, their testimony is admitted with only a perfunctory listing of the examiner’s qualifications and methods. Defense counsel rarely challenges the examiner’s methodology or demands to see the notes and photographs that support the examiner’s opinion.

Challenges to latent fingerprint comparisons and hair and fiber comparisons have begun to show the weaknesses in those long-accepted forms of evidence.1 The time is ripe for similar challenges to firearms identification evidence, which will hopefully result in better scientific studies supporting the theory, better methodology in crime laboratories, and more reliable verdicts.

Under Rule 702 of the Federal Rules of Evidence, an expert, qualified by knowledge, skill, experience, training, or education, may give opinion testimony about scientific, technical, or other specialized knowledge, if it will assist the trier of fact in determining a fact in issue. The trial judge is a gatekeeper tasked with ensuring that the testimony has merit.

The standards for meeting this test have been explained in Daubert2, which sets forth four broad criteria:


A.         Ordinarily, a key question to be answered in determining whether a theory or technique is scientific knowledge that will assist the trier of fact will be whether it can be (and has been) tested.

B.         Another pertinent question is whether the theory or technique has been subjected to peer review and publication.

C.         Additionally, in the case of a particular scientific technique, the court should consider the known or potential rate of error, and the existence and maintenance of standards controlling the technique’s operation.

D.         Finally, “general acceptance” can have a bearing on the inquiry. Widespread acceptance can be an important factor in ruling particular evidence admissible.

 


All scientific testimony, no matter how routinely admitted in the past, must satisfy Daubert.3 In Kumho Tire4, the Supreme Court of the United States stated that the trial court’s gate‑keeping function applies not just to scientific expert testimony as discussed in Daubert, but also to testimony based on “‘technical’ and ‘other specialized' knowledge.’” Firearms identification purports to be a scientific theory reviewable under Daubert.

The Theory of Firearms Identification

The basic theory of firearms identification starts with the fundamental mechanics of a firearm.


When a bullet is fired, the firing pin hits the primer5 with a certain amount of force. The primer in turn ignites the propellant. The propellant burns rapidly, producing gases which exert pressure in all directions — on the rear of the cartridge, on the walls of the cartridge, and on the bullet. The bullet is the only part able to move, and is forced out of the barrel, leaving the cartridge behind.

The barrels of modern rifles and handguns are rifled — parallel spiral grooves are cut into the inner surface of the barrel.6 The space between the grooves is called the lands.7 Shotguns are not normally rifled.8 The grooves twist in a direction (to the right or left). The number of grooves, their width and depth, and the angle of the twist (pitch) vary by manufacturer.

As a bullet passes through the barrel, a little bit of its circumference scrapes the grooves, which force the bullet to rotate. The spin acts like a gyroscope to stabilize the bullet and keep its nose pointed in a consistent direction.9 Because the bullet literally scrapes along the side of the barrel, the groove’s impressions and other microscopic details are etched into the side of the bullet. These marks are called striations or striae.10


Newton’s third law requires an equal and opposite reaction to any action. When a bullet is fired, the cartridge is pressed into the breech (the back of the chamber) by the gas pressure. This impresses any marks on the steel breech face onto the back of the brass cartridge and the primer.11 The cartridge may also be marked by the extractor12, ejector13, or even the lips of the magazine14 in firearms which have these mechanisms. The primer may have a mark from the firing pin.15 These marks are called impressed marks.16


The marks which identify the gross properties of the firearm — caliber, number of lands and grooves, and direction of rifling twist — are the firearm’s class characteristics.17 The marks are often visible to the naked eye. These will be the same for any bullet fired from any firearm of the same make and model, and often of several different makes and models. One theory of firearms identification is that a trained firearms examiner can examine a recovered bullet and determine from the markings on it the weapon’s class characteristics. There are reference works which list the class characteristics for each manufacturer which would enable an examiner to determine what type of firearm was used to fire the recovered bullet.


Firearm identification also assumes that there are individual characteristics which are unique to one specific firearm.18 In theory, is not possible to make two machined surfaces that are microscopically identical.19 Even rifled barrels manufactured consecutively can be distinguished because the cutting and grinding tools are blunted and worn each time they are used, leaving minute variations.20 In addition, wear caused by repeated firing, corrosion, rust, even dirt and debris, will give each firearm barrel unique characteristics.21 Similarly, markings on the breech and firing pin are believed to be unique.22

If a firearm is recovered, the examiner compares microscopic marks on the cartridge or bullet recovered from the crime scene with test bullets and cartridges fired from the recovered weapon to see if the markings are consistent. If no weapon has been recovered, the examiner compares any bullets to each other, and cartridges to each other, to see if the markings are consistent.23

The examiner is looking for a certain quality and quantity of agreement which in turn is mentally compared to the closest known non-match that the examiner can recall seeing. Some differences always exist between a recovered bullet and a test bullet, even if they come from the same weapon.24 Similarly, one would expect some differences between cartridges which come from the same weapon.

One expert, writing in 1959, frequently encountered 15-20% matching striations on land or groove impressions between similar types of bullets known to be fired from different firearms of the same manufacturer and type.25 The percentage of matching striations in bullets fired known to be fired from the same firearm was 21-38%.26 The weight given to a small amount of matching striae is subjective.27


Another expert, writing in 1962, noted that the cartridge will itself have toolmarks from its manufacture, which can produce inconsistent striations in ammunition known to be fired from the same weapon.28 Other problems arise because all marks made by the same tool or machine will bear a strong “family resemblance” to each other.29 Moreover, brass is not a perfectly plastic substance, like wax — a cartridge case may be only imprinted with the “family mark” common to that batch of firearms, not with marks sufficient to distinguish the individual weapon.30 In discussing striations on fired bullets, the author noted the “astonishing differences which seem to be present on bullets which are known to be fired from the same barrel.”31

A more recent work noted that up to 25% of the striae in a non-match and more than 75% of the striae in a match will show concordance.32 The author conceded that it is impossible for two bullets or cartridge casings fired from the same weapon to have absolute concordance in their striae and that there will be some agreement between bullets and cartridge cases fired from different weapons.33

The examiner focuses on how many striae or marks agree. The quality of the agreement is harder to measure. One expert notes that “[i]t is not unusual to find two or three and in rare instances as many as five consecutive straie, but you feel they are not significant because of inexplicable differences in the same of one or more corresponding striae. You sense that they lack the “quality” that you have seen in known match comparisons.”34

When the examiner is satisfied that the agreement exceeds the best known non-match agreement, then he or she can conclude the recovered bullet or casing came from the suspect weapon.


The examiner’s conclusion, based on his observations, is a subjective judgment. There are no objective criteria established in this field.35 Indeed, bullets known to be fired from the same firearm may show astonishing differences.36 Each examiner develops for himself “his own intuitive criteria of identity gained through practical experience.”37

With that theory firmly in mind, does the methodology pass the Daubert standards?

Is Firearms Identification a Science?

             The Plaza court looked at whether fingerprint identification experts were scientists or technicians and concluded that their discipline was not a science.38 The finding that fingerprint examiners are not technicians, not scientists,. is directly applicable to firearms identification examiners. Under Kumho Tire, the distinction between expertise based on science and technical expertise based on practical experience and observation has no effect on the witness’ ability to testify.

Has Firearms Identification Been Adequately Tested?

             The first Daubert criteria is the extent to which the proposed theory has been tested. As set forth in the footnotes above, firearms identification experts have performed a large number of comparisons, the results of which have been published in the trade journal for the Association of Firearms and Toolmark Examiners (AFTE Journal).

The Plaza court concluded that the ACE-V fingerprint comparison method did not adequately satisfy the scientific criterion of testing (the first Daubert factor).39 The Plaza court did not discuss the shortcomings of fingerprint research. An overview of the literature suggests that it shares the same problems with firearms identification research — insufficient statistical testing and insufficient blind and double-blind testing.40


The testing methodology may be fatally flawed. Little statistical analysis has been done to prove the theory.41 The only apparently blind study done yielded an error rate of 9.1%42. A 1995 study of fingerprint examiners yielded an error rate of 22%43 In all but one of the tests described in the AFTE Journal, the examiner apparently knew the sources of the bullets he or she was comparing.44 This strongly suggests that the theory is has not been adequately tested by proper scientific methods.

Are Firearms Identifications Too Subjective?


             The Plaza court had its greatest difficulty with fingerprint comparisons at the stage of comparison where the examiner makes a subjective judgment about the quality of the match.45 In fingerprint comparisons, as with firearms identification, the examiner expects to see some distortions between two fingerprints from the same source which are created by differences in pressure applied by the finger, irregularities in the surface, and differences in the sweat on the finger. Dissimilarities between two rolled fingerprints known to be from the same finger are common — latent prints are never a mirror image of a rolled fingerprint.46 Similarly, the firearms examiner expects differences between known matches, not an identical replica.

Thus, fingerprint comparisons, like firearms identifications are based on the examiner’s subjective opinion about the quantity and quality of microscopic markings which may show a high degree of correspondence without matching, or a small degree of correspondence while matching. The Plaza court initially held that fingerprint examiners could not testify about their opinion that a latent and rolled print matched.47 On rehearing, after the prosecution presented extensive evidence about the FBI’s minimum education and training requirements for its examiners and about its annual proficiency testing, the Plaza court concluded, despite reservations about the adequacy of the FBI’s testing program, that FBI examiners were sufficiently well trained to testify about their opinion under Daubert.48

In Plaza, the trial court’s concerns about subjectivity were answered by a detailed response to challenges about training, proficiency, and procedure within the FBI laboratory. The trial court was not asked to consider the fundamental problem in any subjective comparison with the psychological phenomena known as “confirmation bias”.  If the examiner has a prior belief or expectation that two toolmarks will, or will not, match, then two potential psychological biases arise. "Cognitive confirmation bias" is a tendency to seek out and interpret evidence in ways that fit existing beliefs. "Behavioral confirmation bias," commonly referred to as the self‑fulfilling prophecy, is a tendency for people to unwittingly procure support for their beliefs through their own behavior.49 The danger of confirmation bias affecting an examiner’s subjective opinion is rarely discussed in the firearms examination literature or in the court cases upholding admissibility of the technique.


Confirmation bias has caused famous scientists to fail to report easily visible phenomena that don’t fit their expectations50 and to observe non-existent phenomena.51 Expectations have caused laboratory workers to unconsciously conform test results to an expected norm.52 Logically, that same confirmation bias can cause firearms examiners to overestimate the quality or quantity of straie when they have external reasons to expect a match and to underestimate the quality and quantity of straie when they have external reasons to expect a non-match. So long as the criteria is wholly subjective, confirmation bias may be impossible to avoid. The fingerprint cases have not yet challenged fingerprint comparisons using confirmation basis. It is unclear how prosecutors will respond to these arguments and how receptive the courts will be to this concern.

The basic flaw in the theory underlying individual characteristics is that (1) the bulk of the research has not been done in a blind or double-blind fashion and (2) the standards in the area are entirely subjective, depending solely on the examiner’s own training and experience. It is difficult to conclude that the current state of firearms identification theory passes the first Daubert criteria.

Has Firearms Identification Been Adequately Peer Reviewed and Published?

             The second Daubert criteria is the extent to which the proposed theory has been subjected to peer review and publication. The Plaza court concluded that the fingerprint examiners professional journals did not qualify as peer-reviewed journals as intended by Daubert.53 The same concerns apply with equal force to the articles published in the trade journal for the Association of Firearms and Toolmark Examiners (AFTE Journal).54


The AFTE Journal contains a number of published articles which have been reviewed by the editors of that journal. Again, the studies have rarely been done in a blind or double-blind fashion. This alone should make courts deeply skeptical about the validity of the publication and the peer-review process in this field. It is difficult to conclude that the current state of firearms identification theory passes the second Daubert criteria.

Does Firearms Identification have Acceptable Rates of Error and Standards?

             The third Daubert criteria is a consideration of the error rate of the theory or technique and the standards and controls used to minimize error. As one forensic scientist notes, scientists and courts simply do not have good statistics on error rates in most tests conducted in crime laboratories.55 In most cases, forensic scientists do not have any statistics.56 Tests such as bullet comparison are empirically validated, but have little scientific foundation because they are subjective.57 Careful observation is not good enough.58 Controlled, double-blind tests are needed to validate methods.59

The only apparently blind study done to date yielded an error rate of 9.1%60. That is an unacceptably high error rate. Courts and defense counsel must insist on double-blind testing of laboratories to ensure a reasonable accuracy rate.


In addition, courts and defense counsel must insist upon reviewing the training and certification standards to ensure that the individual examiner has an acceptable accuracy rate. The Plaza court allowed FBI fingerprint experts to testify about their opinion that a latent fingerprint matched a rolled fingerprint only after (1) reviewing the FBI’s minimum standards for its examiners61; (2) the FBI’s annual certification testing62; and (3) requiring the FBI expert to show the jury the actual recovered fingerprint, rolled fingerprint, and such magnified images as necessary to allow the jury to see and understand the basis for the testimony63.

The courts and defense counsel must insist upon reviewing the procedures used by the laboratory64 and the individual examiner65 to ensure that these also match accepted standards in the field and produce an acceptable accuracy rate.


Here again, confirmation bias can play a significant role in distorting test results regardless of the validity of the underlying theory. Evidentiary matter is often presented to forensic scientists in a suggestive manner.66 The examiner is given crime scene evidence (recovered bullets, bullet fragments, and casings), autopsy evidence (recovered bullets and bullet fragments), and often a recovered firearm clearly labeled as the suspect’s.67 This may be accompanied by a written or oral synopsis of the reasons the investigator believes the suspect is guilty.68 In high-profile cases, there may be immense public pressure to validate eyewitnesses statements or an admission with “neutral” scientific evidence. This suggestiveness, coupled with the understandable prosecution sympathies of many examiners, may skew, unconsciously, subjective judgments.69 Confirmation biases may lead the examiner to subconsciously attribute more significance to striae that support the police theory-of-the-case and attribute less significance to striae that conflict with the police theory. Since the literature says that there may be matching striae produced by non-matching tools and non-matching striae produced by matching tools, it is easy for an examiner to interpret the observations to fit his or her expectations. The examiner’s report should include a narrative of what information the examiner had about the case at the time he or she tested the evidence and reached an opinion.

One illustration of this problem occurred in a 1987 experiment involving hair samples. Students who were given hair samples from a crime scene and a suspect in a suggestive manner had a 30.8% error rate; students who were given hair samples from a crime scene and from five possible suspects had a 3.8% error rate.70 Similar errors should be expected from firearms examiners given suggestive information.

Suggestive information given to the examiner after he or she has formed an opinion may affect how confident the examiner is of his or her results. Psychological research on eyewitnesses shows that an eyewitness’ identification of a suspect and his or her confidence in that identification can be significantly affected by suggestions, or even body language, of an investigator who is aware which person in the photo array or line-up is the suspect.71 Firearms examiners are not immune to this sort of influence on their subjective opinions. Counsel and the courts should be skeptical about a firearms examiner who has discussed the case with an investigator before he or she has made a comparison and written his or her report. The examiner’s report should document the examiner’s confidence in his or her results at the time the report was made.


Psychological research on eyewitnesses also shows that an eyewitness’ confidence grows as their trial approaches.72 Eyewitnesses readily revise their confidence estimates upwards, and are less likely to revise them downwards.73 There is no reason to think that experts testifying about their certainty about subjective firearms identifications would be any less affected by this phenomena. Examiners and counsel should be aware of this problem, especially where the examiner’s report is not accompanied by a narrative showing what information was available at the time of the testing and report and the examiner’s confidence at the time of the report.

It is possible for current firearms identification procedures to pass the third Daubert criteria. Courts and counsel need to insist on reviewing the laboratories’ internal quality control procedures, internal testing for error, and any external testing. Courts and counsel should insist that laboratories perform appropriate regular double-blind testing of their methods and personnel. Courts and counsel should insist on procedures that minimize confirmation bias and suggestive presentation of evidence.

Is General Acceptance of Firearms Identification Good Enough?

             The fourth and final  Daubert criteria is a consideration of whether the theory is “generally accepted”. Widespread acceptance can be an important factor in ruling particular evidence admissible.

Firearms identification, like latent fingerprint comparisons, was accepted by the Courts before the standards imposed by Frye and, later Daubert74 and Kumho Tire75. The Plaza court discounted general acceptance within the fingerprint examiner community, but placed significant weight on the adoption of similar methods by the English criminal justice system.76 As challenges to firearms identification are raised, similar comparisons among American laboratories and with laboratories in foreign countries are likely.


General acceptance is not good enough. Not all of the scientific techniques introduced in the early 20th century have withstood scientific scrutiny. For example, the “paraffin test” was widely used to detect gunshot residue on the hands of a person who was suspected of having recently fired a weapon.77 The test was widely accepted by the courts from 1936 until the mid-1960s.78 Although earlier articles had questioned the accuracy of the test, a comprehensive evaluation of the test was not published until 1967 and found it to be unreliable.79 Criminalists rapidly abandoned the test in favor of more reliable techniques.

Widespread acceptance, in the absence of critical scientific testing, is an insufficient guarantee that a method is sufficiently accurate to be introduced in a criminal trial. Recent challenges to latent fingerprint analysis and hair and fiber comparisons80 should alert attorneys that the science underlying firearms identification likewise needs to be critically re-examined under Daubert.

Although current firearms identification theory and procedures pass the fourth Daubert criteria that fact alone should not be good enough to permit firearms identification evidence to be admitted in criminal trials.

Applying Plaza to Firearms Identification

             Firearms identification testimony is often accepted uncritically, with a perfunctory statement of the expert’s credentials, a bare statement of the theory and the expert’s opinion unsupported by photographs of the actual comparison, and with minimal cross examination.

The Plaza court suggests a much more rigorous presentation. The initial order of that court was that:


Accordingly, this court will permit the government to present testimony by fingerprint examiners who, suitably qualified as expert examiners by virtue of training and experience, may (1) describe how the rolled and latent fingerprints at issue in this case were obtained, (2) identify and place before the jury the fingerprints and such magnifications thereof as may be required to show minute details, and (3) point out any observed similarities (and differences) between any latent print and any rolled print the government contends are attributable to the same person. What such experts will not be permitted to do is to present evaluation testimony as to their opinion (Rule 702) that a particular latent print is in fact the print of a particular person. The defendants will be permitted to present their own fingerprint experts to counter the governments fingerprint testimony, but defense experts will also be precluded from presenting evaluation testimony. Government counsel, and defense counsel will, in closing argument be free to argue to the jury that, on the basis of the jurys observations of a particular latent print and a particular rolled print, the jury may find the existence, or non-existence of a match between the prints.81

After rehearing at which the prosecution produced expert testimony about the experts’ training, annual examinations, and about changes in the methods used in the United Kingdom, the court revised its order to permit the experts to testify about their opinion with court oversight.82 Specifically, the trial court said that such evidence would be subject to trial court oversight before presentation to the jury to ensure that the expert was adequately qualified and that the fingerprints offered into evidence were of a quality arguably susceptible to reasonable analysis, comparison, and evaluation.

A similar order would be well advised in firearms identification cases. This would allow the trial court to rigorously examine the expert’s qualifications and training, the method of comparison, and such notes and photographs as are necessary to assure that the evidence was of appropriate quality.

Conclusion

             Firearms identification may be valid and useful evidence in criminal trials. Its adherents simply have not proven their theory with sufficient rigor to pass a Daubert challenge if one is brought in the trial courts.

The experts in this field need to seriously address the problems of confirmation bias in their studies and suggestive information given to examiners. Prosecutors need to insist that these problems be resolved in order to present firearms identification evidence at trial.

Courts should disallow firearms identification testimony which is not accompanied by appropriate proof that the theory and methodology pass scientific scrutiny.

Defense counsel need to be alert to the potential problems in firearms identification evidence and challenge that evidence in appropriate cases.

 


Checklist for Defense Attorneys83

The following is a list of useful questions and issues for defense counsel to consider whenever firearms identification evidence is presented in the courtroom. Some of the questions go to Daubert issues, others go to the underlying reliability of the expert’s opinion.

Ask about the firearms’ experts’ credentials84: training, experience, teaching experience, and professional affiliations.

Ask what books, journals, and magazines the expert considers authoritative. Has the expert published any articles?

Ask about the firearms’ experts’ methodology: protocols, quality control reviews, safeguards, laboratory accreditation.

Did the examiner properly calibrate the microscope at the time of the identification?85

Ask about sources of error: false positives, rate of error, and controls.


Ask to see preliminary reports, notes, pictomicrographs86, photos, and other materials.


Check to see how many test bullets or cartridges were compared.87

Did the expert compare the test bullets and cartridges to each other before examining the suspect bullets and cartridges? Did he or she have any trouble doing so?88

Ask the examiner to explain the difference between class marks, marks from the manufacturing process, and individual marks from that specific weapon.

Did a single expert compare the bullets and cartridges or was it reviewed by a second expert?89

What is the examiner’s standard of agreement for concluding that a specified tool made a specific evidence toolmark? How does this standard compare to others in the examiner’s agency and with any professional organizations he or she may belong to?

Ask whether the examiner has ever intentionally or deliberately compared known non-match bullets?90

Would the examiner expect to find agreement (matching striae) on marks known to have been made from different firearms? How does this match differ from those known non-matches?

Ask whether the examiner’s work has ever been subjected to a blind test or review?91 If so, what was the error rate?

Ask what information the examiner knew at the time he or she examined the marks and suspect firearm.

Is the examiner familiar with various confirmation biases? If so, what precautions does he or she take to minimize their effects?


Consider whether the examiner felt pressured to complete the exam in this case.92

Consider whether the examiner was trying to be “helpful” to the investigation.93

Is the examiner familiar with confirmation bias and, if so, what steps does he or she take to minimize its impact on his or her results.

Make certain that any ammunition used for creating comparison bullets is of the same type as the ammunition recovered from the crime scene.94

If the recovered firearm appears to be newly manufactured, ask examiner about the differences between manufacturing characteristic and those which occur over time through normal wear.

If the recovered ammunition was lead bullets, not jacketed ammunition, ask examiner about the effects of lead deposits on firearms comparisons.95

Is there any possibility the examiner may have intentionally fabricated or falsified the test results?96

 


Unexpected situations that may cause misleading reports:97

These are a few factors mentioned in the firearms literature that may, in rare cases, cause inaccurate results. Defense counsel should be aware of these possibilities and question experts about them when appropriate.

Semi-automatic cartridges fired from revolvers

Revolver cartridges fired from semi-automatic pistols

Pistol bullets fired from rifles using an adapter or having been handloaded into rifle cartridge cases

Replacement of the barrel after the incident

Replacement of the firing pin, ejector and/or extractor after the incident

Refiling of the breech face or firing pin after the incident

Using a round steel ball as the bullet

Using a hardened steel ball of less than the bore diameter

Using a cartridge for which the firearm is not designed, but which it will accept.



*Practicing Attorney, Steele & Associates, Bolton, MA. This article was inspired by research for her presentation at the MCLE Crime Lab: Firearms and Ballistics, Massachusetts Continuing Legal Education, Inc., April 5, 2001.

1See e.g. United States v. Plaza, 179 F. Supp. 2d 492, 57 Fed. R. Evid. Serv. 983 (E.D. Pa. 2002), withdrawn from bound volume and opinion vacated and superseded on reconsideration [hereinafter sometimes referred to as Plaza I], 188 F. Supp. 2d 549, 58 Fed. R. Evid. Serv. 1 (E.D. Pa 2002) (latent fingerprints)  [hereinafter sometimes referred to as Plaza II]; United States v. Mitchell, C.A. No. 96‑407 (E.D.Penn 7/19/99) (latent fingerprints). See also Printing Errors, The Economist, 1/19/02 at 66-67; Fingerprinting Fingerprints, The Economist, 12/16/00 at 89-90; Scheck, Neufeld & Dwyer, Actual Innocence (2000) at 158-171 (hair evidence).

2Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 592-94, 113 S.Ct. 2786, 125 L. Ed. 2d 469, 37 Fed. R. Evid. Serv. 1 (1993).

3Jonakait, Real Science and Forensic Science, 1 Shepard’s Expert and Sci. Evidence Q. 435 (1994) [hereinafter sometimes referred to as Jonakait].

4Kumho Tire Co., Ltd. v. Carmichael, 526 U.S. 137, 119 S.Ct. 1167, 143 L.E.2d 238, 50 Fed. R. Evid. Serv. 1373 (1999).

5The primer is a chemical mixture that ignites when forcefully struck from a certain direction.

6See Moenssens, Starrs, Henderson & Inbau, Scientific Evidence in Civil and Criminal Cases 324 (1995).

7A few firearms have polygonal rifling. Warlow, Firearms, the Law, and Forensic Ballistics 73 (1996) [hereinafter sometimes referred to as Warlow]; Heard, Handbook of Firearms & Ballistics: Examining and Interpreting Forensic Evidence 110, 131 (1997) [hereinafter sometimes referred to as Heard]. Studies claim that identification of polygonal rifling is no more difficult than that of cut-rifled barreling. Valdez, Bullet Identification from H&K USP Polygonal Barrels, 29:3 AFTE J. (1997).

8But see Thownshend, Identification of Rifled Shotgun Slugs, 15:2 J. Forensic Sci. 173 (1970) for an exception to this general rule.

9Warlow, supra note 7 at 8.

10Biasotti & Murdock, The Scientific Basis of Firearms and Toolmark Identification in Faigman, Kaye, Saks, and Sanders, Modern Scientific Evidence ‑ The Law and Science of Expert  Testimony 134 n.6, 152 (1997) [hereinafter sometimes referred to as Biasotti & Murdock]

11Burrard, The Identification of Firearms and Forensic Ballistics 106 (1962) (American printing of 1934 London edition) [hereinafter sometimes referred to as Burrard]; Hatcher, Textbook of Firearms Investigation, Identification, and Evidence 15-16 (1935) [hereinafter sometimes referred to as Hatcher] ; Mazger, et. al., Determination of the Type of Pistol Employed from an Examination of Fired Bullets and Shells, 2 Am. J. Police Sci. 473 (1931); Sinha, Mehrotra & Kumar, Direct Breech Face Comparison, 4 J. Police Sci. & Admin. 261 (1976). See Bonfanti & DeKinder, The Influence of Use of Firearms on their Characteristic Marks, 31:3 AFTE J. 318 (1999) (multiple shots, fouling, and corrosion affect breech marks less than barrel marks).

12Wilson, The Identification of Extractor Marks on Fired Shells, 29 J. Crim. L. & Criminology 724 (1939); Burrard at 119-21.

13Goodard, The Valentine Day Massacre: A Study in Ammunition Tracing, 1 Am. J. Police Sci. 60 (1930) (reprinted in 12:1 AFTE J. 44 (1980); Burrard at 108, 117-119; Warlow, supra note 7, at 74. But see Kennington & Galan, “Ejector” Type Marks on Unfired Cartridges, 19:4 AFTE J. 452 (1987) (documenting ejector-type marks on new, unused ammunition).

14Burrard, supra note 11, at 121-25 (cautioning that magazine lip scrapes may be produced by grit or sand, and that marks from different makes of pistols may look very similar); Warlow, supra note 7, at 73. Moran, The Application of Numerical Criterial for Identification in Casework Involving Magazine Marks and Land Impressions, 33:1 AFTE J. 41, 42 (2001).

15Burrard, supra note 11, at 113; Joling, An Overview of Firearms Identification Evidence for Attorneys. I: Salient Features of Firearms Evidence, 26:1 J. Forensic Sci. 153, 154 (1981) [hereinafter sometimes referred to as Joling I]; Grove, Judd & Horn, Evaluation of SEM Potential in the Examination of Shotgun and Rifle Firing Pin Impressions, 19 J. Forensic Sci. 441 (1974); Grove, Judd, & Horn, Examination of Firing Pin Impressions by Scanning Electron Microscopy, 17 J. Forensic Sci. 645 (1972).

16Biasotti & Murdock, supra note 10.

17Hatcher, supra note 11, at 254.

18Hatcher, supra note 11, at 254-55.

19See e.g. Burrard, supra note 11, at 104, 106-07, 134, 138, 186-87; Hatcher, supra note 11, at 16; Warlow, supra note 7, at 73; Heard, supra note 7, at 110, 124; Nichols, Firearms and Toolmark Identification Criteria, A Review of the Literature, 42:3 J. Forensic Sci. 466, 467-68 (1997); 1 J. Matthews, Firearms Identification 3 (1962).

Moenssens, Starrs, Henderson & Inbau, Scientific Evidence in Civil and Criminal Cases 326-27 (1995) illustrates the difference within the same barrel between its own grooves and lands.

20See Goddard, Who Did the Shooting, Popular Sci. Monthly (Nov. 1927); State v. Campbell, 213 Iowa 677, 693, 239 N.W. 715 (1931); Burrard, supra note 11, at 104-105; Hatcher, supra note 11, at 16-17, 33; Lutz, Consecutive Revolver Barrels, AFTE Newsletter 24 (August 1970); Miller, An Examination of the Application of Conservative Criteria for Identification of Striated Toolmarks Using Bullets Fired from Ten Consecutively Rifled Barrels, 33:2 AFTE J. 125 (2001).

Similar tests on six consecutively machined rifle bolts found a “startlingly” high correspondence of microscopic characteristics. Lopez & Grew, Consecutively Machined Ruger Bolt Faces, AFTE J. 19 (Winter 2000).

211 J. Matthews, Firearms Identification 21 (1962); Hatcher, supra note 11, at 280, 289, 291 (“accidental” marks from dirt, rust, etc.); Heard, supra note 7, at 125-26 (bullets fired months apart, or even numbers of rounds apart may not be matchable); Bonfanti & DeKinder, The Influence of Use of Firearms on their Characteristic Marks, 31:3 AFTE J. 318 (1999) (fine striations caused by internal surface of the barrel is constantly changed by rust, barrel leading, metal fouling, and cleaning). If lead bullets are used, the individual characteristics of the firearm may not be matcheable after 20 to 50 shots. Id. at 320-321. See also Kirby, Comparison of 900 Consecutively Fired Bullets and Cartridge Cases from a 455 Caliber S& W Revolver, 15:3 AFTE J. 113 (1983). If jacketed bullets are consistently used, one study was able to match bullets after 5,000 shots. Id. citing Ogihara, Kubota, Sanada, Fukuda, Uchiyama, and Hamby, Comparison of 5000 Consecutively Fired Bullets and Cartridge Cases from a 45 Caliber M1911A1 Pistol, 21:2 AFTE J. 331 (1989); 15:3 AFTE J. 127 (1983). See also Shem & Striupaitis, Comparison of 501 Consecutively Fired Bullets and Cartridge Cases from a 25 Caliber Raven Pistol, 15:3 AFTE J. 109 (1983).

22Nichols, Firearms and Toolmark Identification Criteria, A Review of the Literature, 42:3 J. Forensic Sci. 466, 469 (1997) The literature suggests that breech and firing pin comparisons are much harder than bullet comparisons. Id.

23Joling I, supra note 15, at 153-54; Munhall, Fundamental Ballistics Pertaining to Investigations Involving Firearms, 6:2 J. Forensic Sci. 215 (1961).

24Hatcher, supra note 11, at 157.

25Biasotti, A Statistical Study of the Individual Characteristics of Fired Bullets, 4:1 J. Forensic Sci. 34, 34-50 (1959).

26Id.

27Biasotti & Murdock, supra note 10, at 143.

28Burrard, supra note 11, at 111, 135; Biasotti & Murdock, “Criteria for Identification” or “State of the Art” of Firearm and Toolmark Identification, 16:4 AFTE Journal 16, 17 (1984) (discussing the toolmarks caused by the die used to impress the headstamp onto a cartridge case).

29Burrard, supra note 11, at 133.

30Burrard, supra note 11, at 133-35.

31Burrard, supra note 11, at 145.

32Heard, supra note 7, at 132, 139 quoting Walls, Forensic Science (1968).

33Heard, supra note 7, at 139.

34Biasotti & Murdock, “Criteria for Identification” or “State of the Art” of Firearm and Toolmark Identification, 16:4 AFTE Journal 16, 17 (1984).

35But see Burrard, supra note 11, at 134 (“any identification based solely on one or two major marking without any finer striations as well should be regarded with suspicion”).

36Peterson, Fabricant, & Field, Crime Laboratory Proficiency Testing Research Program 238, n. 1 (1978) [hereinafter sometimes referred to as LEAA test]. Each lab was sent three .25 caliber bullets fired from two distinct firearms.

37Biasotti, The Principles of Evidence Evaluation as Applied to Firearms and Tool Mark Identification, 9 J. Forensic Sci. 428, 429 (1964); Goddard, Scientific Identification of Firearms and Bullets, 17 J. Crim. L. & Crminology & Police Sci. 254, 262 (1956). See Goddard, A History of Firearms Identification to 1930, 31:3 AFTE J. 225, 239 (1999) (a beginner should be “ultra-conservative” in making an identification until he has enough experience to be “absolutely sure of himself”.

38Plaza I, supra note 1, at 11, 12 (slip op.), Plaza II, supra note 1, at 4-5, 28-29. The Plaza court noted that fingerprint identification was used outside of the criminal justice community to identify deceased victims in mass disasters, for example. Id. at 29. Firearms identification, on the other hand, is only used for criminal justice purposes.

39Plaza I, supra note 1, at 11, 12; Plaza II at 4-5.

40See Cole, Suspect Identities : A History of Fingerprinting and Criminal Identification (2001) (history and criticism of forensic fingerprinting).

41Nichols, Firearms and Toolmark Identification Criteria, A Review of the Literature, 42:3 J. Forensic Sci. 466 (1997); Biasotti, A Statistical Study of the Individual Characteristics of Fired Bullets, 4 J. Forensic Sci. 34 (1959); Biasotti, The Principles of Evidence Evaluation as Applied to Firearms and Tool Mark Identification, 9 J. Forensic Sci. 428, 432 (1964); Deinet, Studies of Models of Striated Marks Generated by Random Process, 26 J. Forensic Sci. 35 (1981).

But see Heard, supra note 7, at 136-38 discussing a simplified statistical analysis.

42LEAA test, supra note 36. Three .25 caliber bullets fired from two distinct firearms were sent to the labs — 5.7% incorrectly reported that all three projectiles had been fired from a single weapon; 3.4% concluded that none of the three projectiles had been fired from the same weapon; thus 9.1% of the reported results were clearly in error.

43Starrs, Forensic Science on the Ropes: An Upper Cut to Fingerprinting, 20 Sci. Sleuthing Rev. 1 (Wint. 1996) (reporting a 22% rate of erroneous identifications in a 1995 survey in which the participants knew they were being tested); Collaborative Testing Services, Forensic Testing Program: Latent Prints Examination, Reports No. 9608, 9708, 9808.

44In a blind comparison of six bullets fired from one of two previously unused consecutively manufactured revolver barrels, examiners were easily able to identify the barrel of origin for each bullet. Lutz, Consecutive Revolver Barrels, 21:2 AFTE J. 120 (1989) [1st published in 1970]. The sample size is extremely small, making the results questionable.

45The court wrote that:

The Daubert difficulty with the ACE-V process is by no means total. The difficulty comes into play at the stage at which, as experienced specialists * * * themselves acknowledge, the ACE-V process becomes subjective namely, the evaluation stage. By contrast, the antecedent analysis and comparison stages are, according to testimony, objective analysis of the rolled and latent prints and comparison of what the examiner has observed in the two prints. Up to the evaluation stage, the ACE-V fingerprint examiners testimony is descriptive, not judgmental.

Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 5 quoting Plaza I.

46Champod & Evett, A Probabilistic Approach to Fingerprint Evidence, 51:2 J. For. Identification 101, 102-03 (2001); Moenssens, Fingerprint Techniques, 260 (1971).

47Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 5-6 quoting Plaza I.

48Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 35-37, 45-46, 48-49, 57-59.

49Nickerson, Confirmation Bias: A Ubiquitous Phenomenon in Many Guises, 2  Rev. Gen. Psych., 175-220  (1998); Snyder, M., Motivational Foundations of Behavioral Confirmation, 25 Advances in Experimental Soc. Psych., 67-114 (1992); Zuckerman, Knee, , Hodgins, Miyake, Hypothesis Confirmation:  The Joint Effect of Positive Test Strategy and Acquiescence Response Set, 68 J. Personality & Soc. Psych., 52-60 (1995).

50Edwin G. Boring, Newton and the Spectral Lines, 136 Science 600, 600-01 (1962) (Sir Isaac Newton’s failure to note absorption lines visible in his apparatus that did not conform to his theory). See generally, Resinger, et als, The Daubert/Kumho Implications of Observer Effects in Forensic Science: Hidden Problems of Expectation and Suggestion, 90:1 Cal. L. Rev. 1 (2002) [hereinafter sometimes referred to as Resinger].

51See e.g. Resinger, supra note 50.

52Berkson, The Error of Estimate of the Blood Cell Count as Made with the Hemocytometer, 128 Am. J.  Physiology 309, 322 (1940); Johnson, Seeing’s Believing, 15 New Biology 60, 79 (1953); Cordaro & Ison, The Psychology of the Scientist:  X. Observer Bias in Classical Conditioning of the Planarian, 13 Psychol. Rep. 787 (1963). See generally, Resinger, supra note 50.

53Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 4, 23, 28-30.

54See Relman & Angell, How Good is Peer Review?, 321 N.E. J. Med. 827 (Sept. 1989). See Collins, Scientific Reliability – Publication, Peer Review and the AFTE Journal, 32:2 AFTE J. 132 (2000) (discussing the editorial and peer review process of that publication).

55Thornton, Courts of Law v. Courts of Science: A Forensic Scientist’s Reaction to Daubert, 1 Shepard’s Expert and Sci. Evidence Q. 475, 481 (1994).

56Id.

57Id. at 482.

58Id. at 485.

59Jonakait, supra note 3, at 435, 440.

60LEAA test, supra note 36, at 238.

61Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 12, n. 2. The FBI’s minimum standard is a bachelor’s degree, preferably as a science major, a two year in-house training program, and a three day certifying examination.

62Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 12-14. The FBI conducted annual examinations for every examiner allowed to testify in court from 1995 to 2001. The test involved comparing a set of latent fingerprints to a number of exemplar prints in a blind fashion. The test takers knew they were being examined and presumably took great care with the results. The FBI expert testified that during those years, there had been only one incorrect result — a false negative (a print reported as non-matching that did in fact come from the same source). A defense expert and the trial court criticized the testing regime as not being rigorous enough in comparison with the difficulty of matching latent prints found at actual crime scenes.

63Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 4-5.

64Warlow states that it is “good policy” to have a second reporting officer confirm any microscopic “match”. Warlow, supra note 7, at 196. See also Hodge, Guarding against Error, 20:3 AFTE J. 290, 293 (1988) (FBI lab policy to have all identifications confirmed by a second examiner).

65See e.g. Brundage, Proficiency Testing in Illinois, 12:3 AFTE J. 76 (1980) (discussing methods and system for testing firearms examiners).

66See Jonakait, Forensic Science: The Need for Regulation, 4 Hav. J. L. & Tech. 109, 160 (1991).

67See id.

68Id.

69Miller, Procedural Bias in Forensic Science Examinations of Human Hair, 11 L. & Hum. Behav. 157, 158 (1987); Kates & Guttenplan, Ethical Considerations in Forensic Science Services, 28 J. Forensic Sci. 972, 972, 975 (1983).

70Miller, Procedural Bias in Forensic Science Examinations of Human Hair, 11 L. & Hum. Behav. 157, 160-61 (1987) (The crime scene sample did not match any of the other submitted samples; the correct answer was “no match”.)

71Wells & Seelau, Eyewitness Identification: Psychological and Legal Policy on Lineups, 1 Psych.Pub.Pol & Law 765 (1995); Nettles, Nettles, and Wells, Eyewitness Identification: “I Noticed You Paused At Number Three”, The Champion 11 (Nov. 1996). See generally Cutler & Penrod, Mistaken Identification: The Eyewitness, Psychology and the Law (1995).

72Cohen, I Could Swear It was Him, Officer, New Scientist, (1/18/97) at 11.

73Id.

74Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579, 113 S.Ct. 2786, 125 L.E.2d 469, 37 Fed. R. Evid. Serv. 1 (1993).

75Kumho Tire Co. v. Carmichael, 526 U.S. 137, 119 S.Ct. 1167, 143 L.E.2d 238, 50 Fed. R. Evid. Serv. 1373 (1999).

76Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 35-37, 45-46, 48-49, 57-59.

77See e.g. Castellanos & Plasencia, The Paraffin Gauntlet, A New Technique for the Dermo-Nitrate Test, 32 J. Crim. L. & Criminology 465 (1941); Diphenylamme Test for Gun Powder, 4 FBI L. Enforcement Bull. 5 (1935)

78See e.g. Brooke v. People, 139 Colo. 388, 339 P.2d 993 (1959) (first successful challenge); Commonwealth v. Westwood, 324 Pa. 289, 188 A. 304 (1936) (first known appellate acceptance)

79Cowan & Purdon, A Study of the “Paraffin Test”, 12 J. Forensic Sci. 19 (1967).

80See United States v. Mitchell, C.A. No. 96‑407 (E.D.Penn 7/19/99) (latent fingerprints). See also Printing Errors, The Economist, 1/19/02 at 66-67; Fingerprinting Fingerprints, The Economist, 12/16/00 at 89-90; Scheck, Neufeld & Dwyer, Actual Innocence (2000) at 158-171 (hair evidence); Saks, Merlin and Solomon, Lessons from the Laws Formative Encounters With Forensic Identification Science, 49 Hastings L.J. 1069, 1105-06 (1998); Berger, Procedural Paradigms For Applying the Daubert Test, 78 Minn. L. Rev. 1345, 1353 (1994).

81Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 4-5 quoting Plaza I.

82Plaza I, supra note 1, at 11, 12, Plaza II, supra note 1, at 58-59.

83The AFTE Journal provided mock testimony in Moran, Firearms Examiner Expert Witness Testimony: The Forensic Firearms Identification Process Including Criteria for Identification and Distance Determination, 32:3 AFTE J. 231 (2000) and some questions in Murdock, Suggested Court Questions to Test Criteria for Identification Qualifications, 24:1 AFTE J. (1992); Moses, Scientific Proof in Criminal Cases – A Texas Lawyer’s Guide, 21:2 AFTE J. 123 (1989) [first published 1970]; Hodge & Blackburn, The Firearms/Toolmark Examiner in Court, 21:2 AFTE J. 232 (1989) [first published 1979].

84Recent examples of experts exaggerating or falsifying credentials make it imperative for counsel to verify each and every expert’s credentials. See Maddox v. Lord, 818 F.2d 1058, 1062 (2d Cir. 1987) (serologist); Doepel v. United States, 434 A.2d 449, 460 (D.C. App. 1981) (FBI serologist); Kline v. State, 444 So.2d 1102 (Fla. App. 1984) (psychologist); People v. Alfano, 95 Ill.App.3d 1026, 1028-29, 420 N.E.2d 1114 (1983) (arson expert); State v. Elder, 199 Kan. 607, 433 P.2d 462 (1967) (lab technician); Commonwealth v. Mount, 257 A.2d 578, 579 (Pa. 1969) (laboratory technician). See also Groner, Your Expert Lied – for 16 years . . ., Legal Times, July 3, 2000 at 8 (pharmacist); Hansen, Inexpert Witness: Lies, resumé fraud take down “expert” before he takes stand again, 87 ABA J. 20 (Feb. 2001) (child abuse expert); Saks, Prevalence and Impact of Ethical Problems in Forensic Science, 34 J. Forensic Sci. 772, 789 (1989); Stars, Mountebanks Among Forensic Scientists, 2 Forensic Science Handbook 1, 7, 20-29 (1988); Caywood, The Role of the Defense Investigator in Firearms Cases, 19:4 AFTE J. 406 (1987).

85Moenssens, Starrs, Henderson & Inbau, Scientific Evidence in Civil and Criminal Cases 330 (1995) explains this process. Essentially the examiner switches the recovered bullet and the test bullet to the opposite stages on the comparison microscope to make sure they indeed match and that the microscope’s optics are perfectly alined.

86Insist on seeing pictomicrographs, even if they are not used as exhibits. There is no way to determine whether the examiner’s opinion is valid without seeing the comparison.

Pictomicrographs are photographs taken of comparison microscope results. See Goddard, A History of Firearms Identification to 1930, 31:3 AFTE J. 225, 239 (1999) (discussing use of photographs to persuade jurors).

If the examiner has not taken pictomicrographs or will not make them available to the defense, defense counsel should be skeptical of the alleged identification. Joling I, supra note 15, at 157. “[W]ithout good photographs evidence of identification must consist merely of statements of opinion, when its value is not very great.” Burrard, supra note 11, at 132. See also Hatcher, supra note 11, at 19; Mathews, Firearms Identification, Vol. 1. 46-50 (1973) (if the author were a juror, he’d want to see the photographs).

Conversely, Heard discourages the use of pictomicrographs in court as they are “at best” illustrative of a stria match and, “at worst” confusing to a lay juror. Heard, supra note 7, at 113, 227. Instead, Heard recommends a video recording of the whole circumference of the comparison. Id; Goddard, A History of Firearms Identification to 1930, 31:3 AFTE J. 225, 239 (1999) (noting the author did not supply jurors with pictures when “we had a ‘poor’ match, pictures of which would serve only to confuse the layman.”); Hodge & Blackburn, The Firearms/Toolmark Examiner in Court, 21:2 AFTE J. 232, 238 (1989) [first published 1979] (jury should never be placed in position of having to interpret photomicrographs as not qualified to do so). Moenssens, Starrs, Henderson & Inbau, Scientific Evidence in Civil and Criminal Cases 333 (1995) explains that examiners are reluctant to use comparison microscope photographs when testifying in court because out-of-focus areas caused by the cylindrical shape of the bullet are hard to explain to jurors and defense attorneys harp on this to discredit the witness.

The FBI’s policy in 1988 was to take photographs representative of its identifications to document what they observed, for review and quality assurance, for pre-trial review, and for trial exhibits. Hodge, Guarding against Error, 20:3 AFTE J. 290, 293 (1988).

One expert was asked in 1963 about the then-common view that “a majority of practitioners today believe no photographs should be introduced voluntarily”, because the passing of photographs distracts the jurors and can raise controversial side issues about the creation of the photographs. The expert responded that “I realize that I’m in the minority. I believe that the photographs should be introduced in court. I believe they should be required. * * * Otherwise, it’s just one man’s word. * * * Well, that to me is not satisfactory.” Howe, Firearms Identification, 31:3 AFTE J. 1999 (reprinting 1963 interview with Dr. Matthews, author of J. Matthews, Firearms Identification (1962), in American Rifleman).

Photographs and digital images are used by firearms examiners to document their work for their own use and for publication. See Moran, The Application of Numerical Criterial for Identification in Casework Involving Magazine Marks and Land Impressions, 33:1 AFTE J. 41, 42 (2001); Kriigel & Brooks, Photography of Bullets Using the Comparison Microscope, 26:1 AFTE J. (1994).

87Burrard, supra note 11, at 148 suggests that one comparison bullet is insufficient, and that no more than five should be created. Warlow says that it is usual in the United Kingdom for at least three cartridges to be fired for comparison purposes. Warlow, supra note 7, at 175. Heard recommends a minimum of four comparison rounds. Heard, supra note 7, at 133.

88See Warlow, supra note 7, at 195-97.

89Warlow states that it is “good policy” to have a second reporting officer confirm any microscopic “match”. Warlow, supra note 7, at 196. See also Hodge, Guarding against Error, 20:3 AFTE J. 290, 293 (1988) (FBI lab policy to have all identifications confirmed by a second examiner).

90Biasotti & Murdock, supra note 10, at 153-154.

91See e.g. Brundage, Proficiency Testing in Illinois, 12:3 AFTE J. 76 (1980) (discussing methods and system for testing firearms examiners).

92Hodge, Guarding against Error, 20:3 AFTE J. 290 (1988). Hodge discusses a case where an examiner mis-identified a bullet has having come from a recovered weapon where the investigators told him that “we know this guy shot the victim and this is the gun he used. All we want you to do is confirm what we already know so we can get a warrant to get the scumbag off the street. We will wait. How quick can you do it?” Id. at 292.

93Hodge, Guarding against Error, 20:3 AFTE J. 290 (1988).

94See Burrard, supra note 11, at 50 (discussing effects of old, damaged, or weak primers, and variability of cartridge diameters). But see Johnson, The Effect of Powder Load and Bullet Material on an Identification, 32:3 AFTE J. (2000) (arguing that reliable identifications may be made regardless of the method of test fire or type of ammunition).

95Bonfanti & DeKinder, The Influence of Use of Firearms on their Characteristic Marks, 31:3 AFTE J. 318 (1999).

96See State v. Ruybal, 408 A.2d 1284, 1285 (Me. 1979) (analysis reported results of tests never conducted); State v. DeFronzo, 394 N.E.2d 1027, 1031 (Ohio C.P. 1978) (analysis reported results of tests never conducted);  In re Investigation of the W. Va. State Police Crime Lab., Serology Dept., 438 S.E.2d 501 (W.Va. 1993) (former head serologist of state crime lab found to have falsified test results in as many as 134 cases over 10 year span); Fricker, Pathologist’s Plea Adds to Turmoil: Discovery of Possibly Hundreds of Faked Autopsies Helps Defense Challenges, 79 A.B.A. J. 24 (March 1993) (Texas pathologist convicted of faking autopsy results).

97This list was derived from Smith, Jokers in the Field of Firearms Identification, 21:2 AFTE J. 131 (1989) [first published 1971] and Mathews, Firearms Identification, Vol. 1. 81-87 (1973). Many of these methods require some familiarity with firearms and firearms identification.