PART I
Context for Ballistic Imaging Analysis



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PART I Context for Ballistic Imaging Analysis

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1 Introduction For  decades,  direct  comparison  of  bullet  and  cartridge  case  evidence  has been used to link crime incidents to other crime investigations to link  specific pieces of evidence to each other and to particular weapons. Since  the  late  1980s,  emerging  technology  has  allowed  such  links  to  be  drawn  between computerized images of bullets and cartridge case evidence. The  development of this technology has led to speculation about its potential  to generate critical investigative leads to possibly related incidents both at  the local level and across broad geographic areas. A specific question that  has been raised concerns the utility of a national reference ballistic image  database  (RBID),  which  would  include  images  from  test-fired  rounds  of  most (if not all) new and imported firearms. In concept, a national RBID  would permit bullet or cartridge case evidence recovered at crime scenes to  be easily and rapidly linked to a firearm’s point of sale—information that  is currently available only if the gun itself is recovered at the crime scene  and is put through a full tracing process (see Chapter 9). The concept of a national RBID differs from existing systems in two  important  ways.  First,  a  national  database  of  ballistic  image  evidence  already exists, but it is not a reference database because it does not collect  test firings from new weapons. In 1997, the Bureau of Alcohol, Tobacco,  Firearms,  and  Explosives  (ATF)  formed  the  National  Integrated  Ballis- tic  Information  Network  (NIBIN);  as  of  2005,  NIBIN  connects  230  law  enforcement agencies, which contribute to a database of images of bullet  and  cartridge  case  evidence  recovered  from  (or  test-fired  from  weapons  linked  to)  crime  scenes.  The  NIBIN  program  equips  agencies  with  Inte- grated  Ballistics  Identification  System  (IBIS)  equipment,  developed  and  

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 BALLISTIC IMAGING manufactured  by  its  contractor,  Forensic  Technology  WAI,  Inc.  (FTI),  of  Montréal, Canada (see Box 4-1 in Chapter 4 for an important note on the  use of the term “IBIS”). The IBIS platform acquires greyscale photographs  of bullet or cartridge case evidence, scoring and ranking pairs of exhibits  by deriving a mathematical signature from images. The scope of NIBIN is  limited by legislative language, prohibiting it from including noncrime gun  evidence in the database.  Second,  RBIDs  do  currently  exist  but  not  at  the  national  level.  Two  states—Maryland and New York—established RBID systems for new hand- guns  sold  in  those  states  in  2000  and  2001,  respectively.  Both  states  use  the same IBIS platform for acquiring images, but are barred from directly  networking their RBID data with crime-scene-based NIBIN data. State leg- islation directed the California Department of Justice to study the feasibility  of establishing an RBID in that state; its assessment in 2001 was that such  a database was not feasible, but suggested that further study be conducted  at  the  national  level.  In  the  wake  of  the  October  2002  sniper  shootings  in the Washington, D.C., area, legislative proposals to create RBIDs were  advanced  or  discussed  in  Connecticut,  New  Jersey,  and  Massachusetts    Butterfield, 2002), as well as Missouri (George, 2004a).1  ( As of 2002, a national-level RBID was said to be under discussion in  Belgium, and “a similar debate is going on in a number of member states of  the European community” (De Kinder, 2002a:198). Recent U.S. Congresses  have seen bills introduced that would create a national RBID, though none  of the bills have advanced past referral to the appropriate committees.2 In  1  Both  chambers  of  the  New  Jersey  state  legislature  have,  at  different  times,  passed  bills  r   equiring some form of ballistic imaging, but not the same bill. In May 2000, the Senate passed  S. 2048 on a 37–0 vote; the bill prohibited sales of handguns unless a “ballistics identifier” was  obtained from the gun and put in a “qualified database.” A “ballistics identifier” was defined  as “a digitized or electronic image of a bullet and shell casing . . . clearly showing the distinc- tive firing pin, ejection, extraction and land marks for that particular handgun.” In November  2002, the Assembly passed A. 438 on a 48–18–10 vote; initial bill text made submissions to an  image database voluntary by handgun owners, but the passed bill had been amended to make  submission of identifiers mandatory for all sold handguns. The bill was not acted upon by the  Senate. In the 2004–2005 session, proposed bills would have required firearms repair shops  to obtain ballistics identifiers for handguns or rifles before returning them to their owners; as  of September 2006, no similar bills had been introduced in either chamber. In Massachusetts,  a Boston police official lauded the idea as a “great law enforcement tool,” pointing to a case  that had been solved using NIBIN (linking the same .22 caliber Ruger pistol to shootings of  seven people in four cities,” as one where an earlier investigative lead to the gun’s purchaser  would have been useful (Butterfield, 2002). 2  ee, e.g., in the 108th Congress, the Technological Resource to Assist Criminal Enforce- S ment (TRACE) Act (S. 469/H.R. 776) and the So No Innocent Person Ever Repeats (SNIPER)  the Sniper Tragedy Act of 2003 (S. 1983), the latter of which incorporated the former in its  entirety, as well as the Bullet Tracing Act to Reduce Gun Violence Act (H.R. 24). In the 107th  Congress, see the Ballistics, Law Assistance, and Safety Technology (BLAST) Act (H.R. 5663) 

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 INTRODUCTION part,  the  bills  did  not  progress  because  they  have  been  caught  up  in  the  nation’s  ongoing  gun  control  policy  debate:  Proponents  see  such  laws  as  essential to reducing gun violence; opponents see them as a first step toward  a national gun registry and a perceived violation of their Second Amend- ment right to bear arms.  In both the 107th and 108th Congresses, bills were introduced in each  chamber  to  require  that  the  National  Academies  conduct  a  study  of  the  state of ballistic imaging technology.3 Independent of that legislation, but  with  a  similar  charge,  the  National  Institute  of  Justice  (NIJ)  of  the  U.S.  Department of Justice requested that the National Academies execute such  a study. 1–A COMMITTEE CHARgE In 2004, as requested by NIJ, the National Academies appointed the  Committee to Assess the Feasibility, Accuracy, and Technical Capability of  a National Ballistics Database. The committee was asked to: assess the feasibility, accuracy and reliability, and technical capability of  developing and using a national ballistics database as an aid to criminal  investigations. To accomplish this, the [committee] will    (1)   ssess the technical feasibility, through analysis of the uniqueness  A of ballistic images, the ability of imaging systems to capture unique char- acteristics and to parameterize them, the algorithmic and computational  challenges of an imaging database, the reproducibility of ballistic impres- sions and the ability of imaging systems to extract reproducible informa- tion from ballistic impressions.    (2)   ssess the statistical probabilities that ballistics evidence presented  A would lead to a match with images captured in a database, whether and  how the base rate can be estimated for those crimes that present bullet or  casing evidence that do in fact come from a gun that produced a database  entry, and the probabilities and consequences of false positives and false  negatives.    (3)   ssess  the  operational  utility  of  ballistics  evidence  in  criminal  A investigations—that  is  the  extent  to  which  it  is  used  or  can  be  used  to  identify crime guns and suspects and to solve specific crimes.   (4)   ssess  the  sources  of  error  in  ballistics  database  matching  (from  A examination, digitization, computer matching, chain of custody and docu- mentation of tests, and expert confirmation), how they may be quantified,  and how these errors interact. and the Bullet Tracing Act to Reduce Gun Violence Act (H.R. 422). Earlier versions of the  Bullet Tracing and BLAST Acts were also introduced in the 106th Congress. 3  ee H.R. 3491 and S. 2581 in the 107th Congress and H.R. 2436 and S. 980 in the 108th  S Congress. These bills also failed to advance beyond referral to subcommittees. 

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 BALLISTIC IMAGING The charge continues: The committee’s work will provide scientific and technical knowledge to  inform the government’s deliberations on three policy options with regard  to ballistics databases:     (1)   aintain  the  National  Integrated  Ballistic  Information  Network  M (NIBIN)  on  ballistics  recovered  from  crime  scenes.  It  is  operated  by  the  Bureau of Alcohol, Tobacco, and Firearms.4   (2)   nhance the NIBIN system so that it can be used to match crime  E scene evidence with the gun used.    (3)   stablish a national ballistics database of images from bullets fired  E from all, or nearly all, newly manufactured or imported guns for the pur- pose of matching ballistics from a crime scene to a gun and information  on its initial owner. We note that the committee was specifically tasked by NIJ to consider  these policy options on the basis of the scientific evidence of system perfor- mance and not to include or exclude options based solely on their cost. That  is, assessing the cost-effectiveness of ballistic imaging and related techniques  is not a dimension of our charge. The wording of the charge raises a few questions. In several instances— as  in  the  formal  name  of  the  committee—the  term  “ballistics”  is  used  in  an  imprecise  manner;  see  Box  1-1.  The  charge  also  provides  no  specific  direction  on  how  the  existing  NIBIN  system  might  be  “enhanced”  in  its  second policy option. The third policy option is also somewhat imprecise  in representing basic assumptions about the nature and intent of a national  RBID; see Box 1-2 (see also Section 9–B in Chapter 9). At the outset, it suffices to say that reasonable proposals for a national  RBID  would  most  likely  focus  exclusively  on  images  of  cartridge  casings  (not bullets, as described in the charge) due to the longer time necessary to  recover  and  process  test-fired  bullets,  and—at  least  at  the  outset—would  likely be further restricted to samples from handguns and small arms. The  charge also suggests that the intent of a national RBID is to provide “infor- mation  on  [a  gun’s]  initial  owner.”  That  is  certainly  the  goal  of  criminal  investigations that would make use of an RBID, but the RBID search itself  would be intended to provide an investigative lead to a point of sale, one  step  removed  from  information  on  the  initial  owner.  As  with  the  current  gun  tracing  system,  additional  investigative  work  based  on  the  point  of  sale would be needed to determine a gun’s initial ownership; as discussed  in Chapter 9, the content of a national RBID does not necessarily involve  entering purchaser-specific data. 4  n January 2003, the agency was renamed the Bureau of Alcohol, Tobacco, Firearms, and  I Explosives, though it commonly retains the acronym ATF.

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 INTRODUCTION BOX 1-1 “Ballistics” Terminology Ballistics, literally, is the study of the dynamics of projectiles in flight. It is not equivalent to “firearms identification,” though in common usage, as in the title of this committee, the word has been interpreted that way. Calvin Goddard— considered the father of modern firearms identification—was chagrined at his own role in initiating this use of language. He titled his landmark 1925 paper on the use of the comparison microscope “Forensic Ballistics,” a name selected “after long and prayerful consideration, and in an effort to employ terms that would be concise and at the same time meaningful;” it was, however, “a title that has plagued me ever since” (Goddard, 1999:233): Forensic was good enough, since it means that which has to do with public disputation, and was what I meant to say. “Ballistics” was bad, very bad, since ballistics strictly used applies solely to projectiles in motion, and the forces that influence that motion. Thus far, I never made an attempt to identify a projectile in motion, and if I ever have to, it will be too soon, so far as I am concerned. However, the man in the street found ballistics [an] interesting word, and seized upon it avidly, at the same time discarding the “forensic” which, when used jointly with ballistics, partly takes the curse off the latter. Likewise, Hatcher (1935:20) rued the way “the word ‘ballistics’ has in the past several years become associated in the public mind with the science of Firearms Identification. . . . I realize fully that usage makes language, and that the recent rather extensive mis-use of the word Ballistics in this way may be a valid excuse for continuing the practice; but still it seems to me that the use of the word to describe the Science of Firearms Identification is somewhat undesirable in any case, as being loose English.” Forensic scientists distinguish between four types of “ballistics” (Rinker, 2004): • Internal ballistics refer to the forces—pressure, ignition, and so forth—that operate on the bullet while still inside the firearm. • External ballistics, closest to the literal definition of ballistics, describes the flight of a bullet between the firearm muzzle and its impact at target. • Terminal ballistics describe the mechanics of impact on both the projectile and the target. • Forensic ballistics, in Goddard’s sense, is the analysis of bullet and car- tridge case evidence and the use of that evidence to link specimens to each other and to particular weapons. “Ballistics” is convenient shorthand but in this report—save for the committee’s formal name—we try to refrain from the use of the word on its own. Our use of the adjective “ballistic” (as in “ballistic imaging” and “ballistics evidence”)—like any instances of “ballistics” that may still appear in the text—is properly interpreted as referring to “forensic ballistics.”

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 BALLISTIC IMAGING BOX 1-2 Content of a Reference Ballistic Image Database A major part of our committee’s charge is to assess the feasibility of a reference ballistic image database. However, many of the parameters governing the content of such a database are not specified by the charge—for instance, whether cartridge casings or bullets (or both) should be entered into the data- base, whether one bullet or casing is sufficient or whether multiple exhibits are needed, whether all firearm types should be covered. The bills introduced at the federal level have been worded to be as inclusive as possible. In the 108th Con- gress, the BLAST Act, SNIPER Act, and TRACE Act (H.R. 5663, S. 1983, and H.R. 776, respectively) bore identical language on the nature of the envisioned database. “A licensed manufacturer or licensed importer” would be required to (A) test fire firearms manufactured or imported by such licensees as specified by the Attorney General by regulation; (B) prepare ballistic images of the fired bullet and cartridge casings from the test fire; (C) make the records available to the Attorney General for entry in a com- puterized database; and (D) store the fired bullet and cartridge casings in such a manner and for such a period as specified by the Attorney General by regulation. The database envisioned by these bills would require both bullets and casings to be entered; it would also put the responsibility for image acquisition and exhibit archival on the manufacturers or importers. The question of whether image data would be collected for long guns as well as handguns was not directly answered. The existing state reference ballistic image databases in Maryland and New York both made key limiting assumptions, restricting their content to cartridge In structuring our work, we have taken the three policy options as a  guide; addressing them necessarily involves addressing the issues suggested  in  the  preceding  four  substantive  points  of  the  charge.  Cast  in  language  more consistent with usage in the field, we have interpreted our principal  task as providing information on three different federal policy options: . Maintain the NIBIN  as  it  presently  exists—that  is,  retaining  the  restriction  that  only  crime-gun-related  evidence  be  included  in  the  database. . Enhance the current NIBIN system in order to increase its effective- ness without expanding its scope to include new or manufactured firearms;  such  improvements  could  include  changes  to  the  basic  imaging  standard  used  by  the  system  (e.g.,  three-dimensional  surface  measurement  rather 

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 INTRODUCTION casings from handguns only. The enabling law in Maryland created a centrally located “Statewide Shell Casing Data Base,” later called MD-IBIS, and a “State- wide Shell Casing Repository,” both to be administered by the Maryland State Police Crime Laboratory. The shell casings in question were to be “provided by dealers from all handguns sold in the state” and transmitted to the Crime Labora- tory (Maryland Code 29.05.02.02). In later years, a bill to expand MD-IBIS cover- age to long guns was introduced in the legislature but was not enacted. Similarly, the New York Combined Ballistic Identification System (CoBIS) database was established as the “pistol and revolver ballistic identification databank” (New York General Business Laws, Article 26, Section 396-ff): Any manufacturer that ships, transports or delivers a pistol or revolver to any person in this state shall . . . include in the container with such pistol or revolver a separate sealed container that encloses: (a) a shell casing of a bullet or projectile discharged from such pistol or revolver; and (b) any addi- tional information that identifies such pistol or revolver and shell casing. The language of the previous federal bills notwithstanding, we generally assume throughout this report that a national reference ballistic image database would be similar to the Maryland and New York models albeit at the larger, national scale. At the minimum, we assume that operational constraints would limit the national reference database to cartridge casings, owing to the time- consuming process of discharging weapons in a water tank or other trap so that expended bullets can be recovered in “pristine” condition. Whether rifles and long guns would be included in such a database is an open question; again, the Maryland example leads us to assume that initial coverage would be focused on handguns (as the major class of guns used in crime). than two-dimensional photography), improvements to database handling,  improved procedures for working with the existing hardware and software,  and so forth. . Establish a national reference ballistic image database, as a coun- terpart  to  (and  possibly  linked  to)  NIBIN,  containing  images  of  ballistic  samples from all newly manufactured or imported guns, in order to gener- ate investigative leads to the original point of sale of a firearm.  1–A.1 Experimental Study by National Institute of Standards and Technology In support of the committee’s work, NIJ separately contracted with the  Office of Law Enforcement Standards of the National Institute of Standards 

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 BALLISTIC IMAGING and  Technology  (NIST)  for  experimental  work  with  the  direction  and  advice  of  the  committee,  on  the  feasibility  and  accuracy  of  identification  using a national ballistic image database. In particular, the NIST work con- siders the relative advantages of three-dimensional metrology techniques as  compared to the current two-dimensional imaging used in NIBIN. NIST’s  experimentation in support of this study builds on NIST’s ongoing work,  under other contracts, on the development of standard bullets and cartridge  casings for the calibration of ballistic imaging systems. The NIST work is  summarized  in  Chapter  8,  and  the  full  NIST  report  has  been  published  separately (Vorburger et al., 2007). 1–A.2 Limitations: What the Committee Study Does Not Do In the balance of this chapter, we provide additional basic context for  the committee’s work and give an overview of the structure of the report.  However,  we  believe  that  it  is  first  important  to  be  clear  on  certain  limi- tations  of  our  work  and  our  charge.  Our  task  is  to  assess  various  policy  options related to ballistic imaging; it is possible for this basic charge to be  misconstrued or overinterpreted in at least three major ways. First,  and  most  significantly,  this study is neither a erdict on the uniqueness of firearms-related toolmarks generally nor an assessment of the alidity of firearms identification as a discipline. Our charge is to focus on  “the uniqueness of ballistic images”—that is, on the uniqueness and repro- ducibility of the markings (toolmarks) left on cartridge cases and bullets as  they are recorded or measured by various technologies (e.g., photography  or surface metrology).  The  uniqueness  of  firearms-related  toolmarks  generally  is  a  much  broader  question—and  a  very  important  one—but  it  is  not  one  that  our  committee was constituted to address. At a minimum, assessing the general  validity and uniqueness of toolmark evidence would require a much wider  range of gun and ammunition selections and firing conditions than was sup- ported in our experimentation through NIST (see Chapter 9). It would also  require precise quantification of the myriad sources of variability inherent  in the firing of a gun (see Chapter 2). In short, it would be a major under- taking, requiring a sustained program of research over many years, and it is  impossible to definitively answer the question of the uniqueness of ballistic  toolmarks as a by-product of a more targeted study of the uniqueness of  ballistic images. Although  a  definitive  statement  on  firearms  toolmark  uniqueness  is  not within our purview, some discussion of issues related to uniqueness— particularly  the  sources  of  variability  in  generating  such  toolmarks—are  essential to our work. Chapters 2 and 3 of this report are largely dedicated  to  these  matters,  covering  the  sources  of  variability  inherent  in  firing  a 

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9 INTRODUCTION gun and the uniqueness and reproducibility of firearms-related toolmarks  as judged by firearms examiners using the comparison microscope. From  these reviews, some readers may attempt to infer a stance by this commit- tee,  for  or  against  the  validity  of  firearms  identification  generally.  From  this perspective, some may argue that our narrow focus on the uniqueness  of  ballistic  images  amounts  to  missing  the  proverbial  elephant  standing  in the room: that is, we should extend any conclusions on the strength or  weakness of ballistic image evidence to infer the strength or weakness of  ballistic toolmark evidence more globally. We reiterate that no such broader  conclusion is intended by this report, which was not developed to support  more  sweeping  statements.  Rather,  the  examination  in  Chapters  2  and  3  is intended to identify major sources of variability, as well as particularly  challenging  (or  easy)  contexts  for  linking  pieces  of  ballistics  evidence,  in  order to best construct our experimental work with NIST and understand  the results of ballistic image database comparisons. Other  readers  may  see  a  definitive  statement  on  the  uniqueness  and  reproducibility of toolmarks as a first and necessary building block to any  further  work:  without  such  a  statement—if  firing  processes  and  resulting  toolmarks are completely random—then the basic utility of a ballistic image  database (of any sort or scope) to try to suggest connections between pieces  of evidence comes into question. We appreciate this argument but conclude  that  it  is  possible  to  speak  meaningfully  about  ballistic  image  database  performance  without  first  fully  accepting  or  concluding  the  fundamental  uniqueness  of  toolmarks.  In  this  regard,  the  analogy  of  fingerprints  may  be useful: to date, there exists no definitive proof that no two people can  have  identical  fingerprints.  Instead,  the  credence  of  fingerprint  evidence  rests mainly on the assertion that—across all the years in which fingerprints  have been manually compared—no two people sharing the same individual  prints  has  yet  been  found.  The  emergence  of  computerized  image  data- bases for fingerprints has served not only to facilitate links between pieces  of  evidence,  but  also  to  allow  for  further  probing  of  basic  assumptions.  Searches across large databases of fingerprint images begin to add quanti- tative weight to the claim of fundamental uniqueness, and reconciliations  between  manual  examinations  and  computer  algorithms  generate  useful  debates over how many specific points of similarity must be found before a  match can be determined. In time, ballistic image databases may similarly  be an important resource for evaluating the basic assumptions of firearms  identification; however, development and study of image databases need not  wait until those basic assumptions are definitively examined. Second, our work is not intended to speak to the question of whether firearms identification by a human firearms examiner can be replaced by mechanical routines.  A  point  that  we  return  to  throughout  in  the  report  is the distinction between systems designed for search and those designed 

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0 BALLISTIC IMAGING for erification; the two are very different, although commonly confused.  NIBIN was designed as a search tool and not for verification, and  as  we  argue,  ballistic  image  databases  are  most  appropriately  seen  as  tools  for  search.  For  ballistics  evidence,  verification  is  formally  made  by  experi- enced firearms examiners, who provide sworn expert testimony on evidence  matches in court: hence, only direct physical examination of exhibits—and  the  judgment  of  a  human  firearms  examiner—can  certify  a  “hit,”  or  a  “true”  match.  Our  focus  is  on  the  question  of  whether  ballistic  imaging  technologies perform reliably as a search tool to assist human examiners— spanning large volumes of image data and returning high-likelihood candi- date matches for an examiner to consider—and not on whether computer  technology can replace human examiners. Third,  the proposal for this study explicitly precluded the committee from assessing the admissibility of forensic firearms eidence in court, either  generally or in specific regard to testimony on ballistic imaging comparisons.  We  note,  however,  that  high-subjectivity  branches  of  forensic  science  are  now confronting growing skepticism with regard to discernible uniqueness  as  a  result  of  a  number  of  legal  and  scientific  studies.  The  standard  for  scientific evidence created by the U.S. Supreme Court’s decision in Daubert . Merrell Dow Pharmaceuticals (509 U.S.  579, 1993) places high proba- tive weight on quantifiable evidence that can be tested empirically and for  which known or potential error rates may be calculated, such as identifica- tion using deoxyribonucleic acid (DNA) markers (Saks and Kohler, 2005;  National Research Council, 1996). The legal context in which ballistic image  evidence  may  be  presented  is  too  important  to  steer  clear  of  entirely,  and  we briefly review some of the relevant legal issues and cases in Chapter 3.  However, we do not in any way offer a determination of whether ballistics  evidence should or should not be admissible in court proceedings. 1–A.3 Microstamping Over  the  course  of  the  committee’s  deliberations,  debates  over  the  feasibility  of  alternatives  to  imaging  technologies  that  would  achieve  the  same basic goal as a national RBID—providing an investigative lead to a  point of sale—have grown in prominence. Of particular interest is the use  of microstamping to directly imprint firearm parts or ammunition so that  known, unique markers are imparted on bullets or cartridge casings and a  connection can be made to a gun (and its point of sale) without recovery of  the gun itself. The technology is also sometimes referred to as “ballistic ID  tagging” or “virtual serial numbering.” Just as the issue of creating RBIDs  grew in prominence when it came under serious consideration in the state  of California, so, too, has legislative attention in the nation’s largest state  fueled  debate  over  microstamping.  Versions  of  bills  requiring  some  form 

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 INTRODUCTION of microstamping passed in one chamber of the California legislature (but  not  both)  during  the  2005–2006  session.  However,  in  September  2007,  AB  1471—a bill requiring microstamping on parts of new semiautomatic  handguns sold in the state after January 2010—was passed by the legisla- ture and was signed into law by the governor in October. Microstamping has grown sufficiently in stature that no bill before the  109th or (as of August 2007) 110th U.S. Congresses called for a national  RBID; instead, one repeatedly introduced bill on ballistic imaging has been  changed in focus to require the use of microstamping.5 Though the feasibil- ity of a national RBID remains the committee’s primary focus, we also con- sider the feasibility of alternative technologies to achieve the same goal. 1–A.4 Committee Activities In carrying out its charge, the committee held six meetings beginning in  February 2004, the first four of which included public sessions. Given the  committee’s size and the multiple subject areas contained in its charge, the  committee conducted much of its work in small working groups, including  one set up to provide specific guidance to the NIST experimentation portion  of the study. Committee members and staff visited local NIBIN installations  at law enforcement agencies and the headquarters of Forensic Technology  WAI,  Inc.,  makers  of  the  computer  platform  on  which  NIBIN  presently  operates.  Committee  subgroups  were  also  permitted  to  perform  limited  experimentation using New York State’s CoBIS RBID and the ballistic image  database  maintained  by  the  New  York  City  Police  Department,  which  is  not actively linked to NIBIN but uses the same technology. To get a sense  of sources of variability in bullet and cartridge markings, committee sub- groups visited three firearms and ammunition manufacturers: Beretta USA,  Hi-Point  Firearms,  and  Federal  Cartridge.  Finally,  committee  subgroups  examining alternative technologies visited developers of microstamping or  tagging technologies for both firearms parts and ammunition.  1–b CONTExT: THE guN CRIME PRObLEM The  primary  motivation  for  considering  the  implementation  of  a  national  RBID—and  for  the  analysis  and  matching  of  ballistics  evidence,  5  ee  H.R.  5073,  the  Technological  Resource  to  Assist  Criminal  Enforcement  (TRACE)  S Act, in the 109th Congress. Introduced in April 2006, it was referred to the House Judiciary  Committee but no further action was taken prior to adjournment. The same legislation was  introduced in the House in the 110th Congress as H.R. 1874 on April 17, 2007, following  the mass shooting at Virginia Polytechnic Institute and State University.

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 BALLISTIC IMAGING in general—is to reduce gun-related crime.6 Ballistics evidence matching is  intended to assist police investigations of crimes involving firearms, thereby  increasing  the  chance  of  arrest,  conviction,  and  punishment  of  criminals.  The desired result is the incarceration of gun-using criminals and the deter- rence of gun crime: if a higher percentage of such criminals are incarcerated,  it may deter other criminals from using guns, and incapacitate those who  get caught from committing further crimes (see, e.g., Nagin, 1998).  Although  gun  crime  constitutes  a  small  percentage  of  violent  crimes,  guns are used in two-thirds of homicides. Criminal assaults with guns are  more lethal in comparison with those involving other  common weapons,  and  the  misuse  of  guns  by  criminals  creates  a  sense  of  insecurity,  of  “no  safe place” for residents of a neighborhood where gunfire is common. The  social  costs  of  gun  violence  in  the  United  States  include  both  the  direct  damage of injury and death to victims and the indirect damage to the larger  population  whose  quality  of  life  is  reduced  by  the  threat  of  gun  violence  (Cook  and  Ludwig,  2000).  In  general,  property  values,  business  location  decisions,  commuting  routes,  and  other  lifestyle  choices  are  influenced  by the public’s perception of the threat of gun violence. The Washington,  D.C., sniper attacks of 2002 are an extreme example that directly affected  an entire metropolitan area; for some inner-city neighborhoods, gunfire is  a routine occurrence that places the public in fear and distorts day to day  living (Cook and Ludwig, 2002). The total annual social cost of gun crime  is estimated to be $80 billion (Ludwig and Cook, 2001). Thus, tools, such  as ballistic imaging technology, that can assist police in solving gun-related  crime have a clear benefit for the population at large, particularly if they  have some deterrent effect on gun violence. The Federal Bureau of Investigation’s Uniform Crime Reports (UCR)  program provides yearly data on the number of firearm crimes known to  the  police.  The  UCR  figures  are  based  on  counts  of  the  number  of  mur- ders, robberies, and aggravated assaults committed with firearms. In 2003,  there  were  282,641  reported  total  firearms  crimes  comprised  of  137,657  (48.7 percent) robberies with firearms, 135,346 (47.9 percent) aggravated  assaults with firearms, and 9,638 murders with firearms (3.4 percent).7 As  shown in Figure 1-1, the yearly number of crimes committed with firearms  in the United States fluctuated between 300,000 and 400,000 between 1973  and 1988, increased over the next 5 years to a peak of 581,697 in 1993,  6  he nature of gun-related crime and the adequacy of existing data related to it are com- T prehensively reviewed in National Research Council (2005). 7  eparate  estimates  for  2003  by  the  National  Center  for  Injury  Prevention  and  Control  S of  the  Centers  for  Disease  Control  and  Prevention  indicate  approximately  47,000  nonfatal  gunshot injuries for which the intent of the injury was violence-related. The data are gener- ated  from  the  center’s  National  Electronic  Injury  Surveillance  System;  see  http://www.cdc. gov/ncipc/wisqars [accessed February 2008].

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 INTRODUCTION 700,000 Total Number of Firearms Crimes 600,000 500,000 400,000 300,000 200,000 100,000 0 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year FIguRE 1-1 Crimes committed with firearms, 1973–2003. SOURCE:  Federal  Bureau  of  Investigation,  Crime in the United States  (annually;  1-1.eps see http://www.ojp.usdoj.gov/bjs/ [accessed February 2008]). decreased dramatically over the course of the 1990s, and remained stable  through 2003. Firearms crime rates per 100,000 U.S. residents followed the  same trajectory; see Figure 1-2.  UCR data on the yearly number of homicides committed with firearms  between 1973 and 2003 follow the same trajectory as the total number of  firearms  crimes  per  year;  see  Figure  1-3.  However,  the  peaks  and  valleys  were  more  pronounced  in  the  gun  homicide  trend  data.  Gun  homicides  peaked  in  3  years:  1974,  1980,  and  1993.  After  1993,  there  was  a  steep  decrease to 1999. Gun homicide rates follow a similar trajectory; however,  when population size is considered, the 1974 and 1993 peaks are the same  (6.6  gun  homicides  per  100,000).  The  steep  increase  in  gun  homicides  beginning in the 1980s and peaking in 1993 was largely driven by minor- ity youth in urban settings (Cook and Laub, 2002; Blumstein, 1995). The  youth gun violence epidemic was further concentrated among highly active  criminal offenders who tended to be involved in street gang or illegal drug  activity  (Braga,  2003;  Kennedy  et  al.,  1996).  In  most  cities,  gun  violence  problems remain concentrated among a small number of criminally active  youth who are involved in gangs or criminal groups (Braga et al., 2002).  Cities  vary  widely  in  the  amount  of  gun  crime  they  experience  and 

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 BALLISTIC IMAGING 250.0 Rate per 100,000 Residents 200.0 150.0 100.0 50.0 0.0 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 Year FIguRE 1-2 Firearms crime rates, 1973–2003. SOURCE:  Federal  Bureau  of  Investigation,  Crime in the United States  (annually;  1-2.eps see http://www.ojp.usdoj.gov/bjs/ [accessed February 2008]). 20,000 18,000 16,000 14,000 Number of Victims 12,000 10,000 8,000 6,000 4,000 2,000 0 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 Year FIguRE 1-3 Homicides committed with firearms, 1973–2003. 1-3.eps SOURCE:  Federal  Bureau  of  Investigation,  Crime in the United States  (annually;  see http://www.ojp.usdoj.gov/bjs/ [accessed February 2008]).

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 INTRODUCTION the  numbers  of  crime  guns  local  police  departments  recover.  Table  1-1  presents  gun  homicide  counts  and  rates,  as  well  as  the  number  of  crime  guns recovered, for 32 cities that participated in ATF’s Youth Crime Gun  Interdiction Initiative (YCGII) in 2000 and were judged by ATF to be sub- mitting all recovered firearms for tracing (U.S. Bureau of Alcohol, Tobacco,  TAbLE 1-1 Gun Homicides and Crime Gun Recoveries in 32 Cities in 2000 Homicide Rate   City Gun Homicides per 100,000 Gun Recoveries Atlanta, GA 108 25.9 1,141 Baltimore, MD 202 31.0 4,295 Baton Rouge, LA 33 14.5 1,068 Boston, MA 26 4.4 896 Camden, NJ 17 21.3 165 Charlotte, NC 57 9.1 2,041 Chicago, IL 415 14.3 8,570 Cincinnati, OH 7 2.1 877 Dallas, TX 177 14.9 3,005 Gary, IN 56 54.5 792 Houston, TX 165 8.4 3,909 Indianapolis, IN 67 8.4 3,592 Los Angeles, CA 430 11.6 3,877 Louisville, KY 33 12.9 1,637 Memphis, TN 110 16.9 3,244 Milwaukee, WI 90 15.1 2,283 Minneapolis, MN 38 9.9 949 Nashville, TN 56 10.5 2,297 New Orleans, LA 175 36.1 1,965 New York, NY 434 5.4 6,284 Newark, NJ 40 14.6 584 Oklahoma City, OK 24 4.7 856 Philadelphia, PA 259 17.1 3,041 Phoenix, AZ 110 8.3 4,778 Piedmont Triad, NCa 38 7.7 699 Portland, OR 14 2.6 857 Richmond, VA 53 26.8 1,109 Salinas, CA 16 10.6 327 San Antonio, TX 45 3.9 1,294 San Jose, CA 8 0.9 1,476 St. Louis, MO 90 25.8 2,612 Tucson, AZ 49 10.1 2,135 aGreensboro, High Point, and Winston-Salem, NC. SOURCES: Gun homicide data from FBI Supplementary Homicide Reports, 2000; see http:// www.icpsr.umich.edu [accessed February 2008]. Gun recovery data from U.S. Bureau of Al- cohol, Tobacco, and Firearms, 2002.

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 BALLISTIC IMAGING and Firearms, 2002; see Box 9-1). Not surprisingly, large cities—New York,  Los Angeles, and Chicago—report the largest numbers of gun homicides.  However, there are smaller cities that experience dramatically higher rates  of gun violence relative to the large cities. Gary, Indiana, had the highest  rate of gun homicides per 100,000 residents with 54.5, followed by New  Orleans  with  36.1  percent,  and  Baltimore  with  31.0  percent.  Because  of  the variability in gun crime rates by locality, different localities may have  different baseline needs for ballistic imaging technology (and, potentially,  different levels of benefit from its refinement). 1–C bALLISTIC IMAgINg, FIREARMS IDENTIFICATION, AND “bALLISTIC FINgERPRINTINg” Analysis of ballistics evidence may provide a link between two shooting  incidents if it is determined that the same weapon was fired in both. That  information may be helpful to investigators since it suggests that the inci- dents involved the same shooter, or involved two shooters who were linked  by the transfer of the gun in question. Alternatively, the ballistics evidence  match can provide a link between a shooting incident and a particular gun,  perhaps one that has separately been found and placed in police custody;  this information may be helpful to the investigation if the identity of the  owner or possessor of that gun is known or could be determined through  further investigation. It is important to clarify several terms and the distinctions among them.  First, ballistic imaging is not identical to firearms identification. Traditional  firearms  identification  techniques,  relying  on  the  direct  viewing  of  speci- mens under a comparison microscope by a trained firearms examiner, have  been  used  in  investigations  for  decades.  As  discussed  in  Section 1–A.2,  the  identification  and  confirmation  of  fired  bullets  or  cartridge  cases  as  having  been  fired  from  a  specific  firearm  is  the  responsibility  of  human  e   xaminers. Ballistic imaging is a means of searching across a large number  of exhibits—in greater numbers and across broader expanses of geography  than a human examiner could possibly achieve—to suggest possible match- ing candidates. Ballistic imaging would more accurately be described as a  form of computer-assisted firearms identification. The unique innovation that ballistic imaging technology has added to  the field is the “cold hit”—the generation of possible links between speci- mens and cases arising only through querying a database. A cold hit can  be particularly valuable for furthering the investigation of shooting crimes  that  lack  an  obvious  suspect  or  even  any  clear  leads.  Research  on  police  clearance  of  homicide  cases  (Wellford  and  Cronin,  1999,  2000)  suggests  that the availability of witnesses (who can identify the offender or victim  and who may be able to suggest the whereabouts of the offender) and swift 

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 INTRODUCTION action by the first officers on the scene are major contributors to success  in closing a case. By comparison, crimes for which eyewitness testimony is  not available (or where witnesses may be unwilling to come forward), such  as is common in drug-related homicides, are harder to solve. In cases for  which witnesses and early data on possible suspects are lacking, a cold hit  on  ballistics  evidence  generated  through  a  routine  database  search  could  provide an important investigative lead. Generally,  ballistic  imaging  offers  the  opportunity  for  more  rapid  searching across a high volume of candidates than is possible using conven- tional techniques. In traditional firearms identification, a firearms examin- er’s cognitive task in examining specimens under a comparison microscope  is to form a mental pattern of identifying marks and features on bullet and  cartridge case evidence and to match that pattern against those from other  exhibits. Accordingly, searching through large amounts of ballistic evidence  and  verifying  a  match  can  be  a  very  labor-intensive  and  time-consum- ing task. Making connections between  different cases  relies on  the  visual  memory  of  the  firearms  examiner  or—if  all  exhibits  are  not  viewed  and  remembered by the same person—recognition of features from photographs  in open case files or posts on bulletin boards. Ballistic imaging technology  allows  images  of  bullets  or  casings  to  be  cataloged,  indexed,  scored,  and  ranked.  A  firearms  examiner  can  visually  compare  high-ranked  pairs  of  images on the screen, much as a radiologist might read a digital mammo- gram or other X-ray, and the physical evidence items for promising matches  can then be requested as appropriate for confirmation. The general ballistic imaging methodology we describe in this study has  been popularly referred to as ballistic fingerprinting, a term that carries both  positive and negative connotations and that is misleading in a very impor- tant sense. Most commonly used in relation to a national reference ballistic  image database, with the idea of logging a newly sold gun’s “fingerprint”  before  or  as  a  condition  of  sale,  “ballistic  fingerprinting”  naturally  sug- gests a connection to the more widely known practice of recording human  fingerprints.  What  is  fundamentally  misleading  about  equating  “ballistic  imaging” and “ballistic fingerprinting” is the point of reference—a human  fingerprint is an attribute of that human, and a determined match between  a latent fingerprint found at a crime scene and a fingerprint in police files  suggests a direct connection between a crime and a suspect. However, the  markings imparted to fired bullets and casings are attributes of a firearm,  not the person who fires it.8  8  hough  “ballistic  fingerprinting”  has  become  a  popular  term  in  recent  years,  references  T to ballistic toolmarks as mechanical fingerprints date back to the formative days of firearms  identification. Hatcher (1935:265, 275), one of the seminal texts in the field, notes that “these  [toolmarks] are what might very aptly be described as the ‘finger prints of the firing pin and 

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 BALLISTIC IMAGING Absent other evidence, firearms identification and ballistic imaging do  not automatically generate a mapping from ballistics evidence to a possible  perpetrator.  We  return  to  this  point  in  Section  3–A,  but  it  is  important  to  note  here  that  fingerprint  (and  DNA)  evidence  refer  to  attributes  of  a  particular person, but they do not necessarily point to that person as the  criminal offender. That is, the presence of this evidence can place a person  at the location of a crime, but not necessarily demonstrate that they were  there at the time of the crime or that they committed the act in question.  The intent of a national RBID is to provide a relatively quick connection  between recovered ballistics evidence and a point of sale. However, addi- tional work from a national RBID “hit” would still be necessary to derive  a person’s name from the point of sale and that this person—the original  purchaser of the firearm—is not necessarily the person who used the gun  in crime. 1–D OvERvIEW OF REPORT Part  I  of  this  report  describes  the  context  for  ballistic  image  analy- sis.  Chapter  2  describes  the  toolmarks  imparted  on  bullets  and  cartridge  c   asings as a result of firing, reviewing the sources of variability inherent in  the manufacture of firearms and in the process of firing a gun. Chapter 3  describes the nature of ballistics evidence in more detail, focusing on tra- ditional  firearms  identification  techniques  and  the  studies  that  have  been  performed on the uniqueness and reproducibility of firearms-related tool- marks as discerned using conventional microscopy. Part II deals with the current state of ballistic imaging and the existing  national image database, NIBIN. Chapter 4 discusses the technology used  for acquiring images and scoring and ranking them, focusing on the IBIS  platform  used  by  the  NIBIN  program.  Chapter  5  describes  the  evolution  of  the  NIBIN  program  and  its  structure  and  summarizes  what  is  known  about the NIBIN system’s performance. Drawing from both these chapters,  Chapter  6  outlines  operational  and  technical  enhancements  that  could  improve NIBIN. Part  III  addresses  the  basic  titular  charge  to  the  committee,  describ- ing evidence on variability in ballistics evidence and the implications for a  national reference ballistic image database. Chapter 7 introduces a major  technical  enhancement  that  the  committee  chose  to  explore  as  an  option  breech block on the primer.’” If all the gross, class marks are the same between two bullets,  “this does not, however, prove in any way that [a suspect bullet] came from that particular gun  as there are hundreds or even thousands of guns of each type manufactured. . . . Fortunately,  however, each and every barrel has its own ‘finger prints’ which it leaves on a bullet, and iden- tification by these marks is just as certain as identification of a criminal by his finger prints.”

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9 INTRODUCTION for  either  the  current  NIBIN  program  or  a  wide-scale  national  refer- ence  database.  That  enhancement  is  the  replacement  of  two-dimensional  p   hotography  with  three-dimensional  topography,  and  we  briefly  describe  that  technology  along  with  historical  alternatives  to  photography  in  fire- arms  analysis.  Chapter  8  reviews  the  experimental  efforts  conducted  by  NIST in support of the committee’s work, as well as limited experimental  work using the New York State CoBIS database. Chapter 9 builds from the  new experimental evidence and from studies (described in Chapter 4 and  elsewhere) in articulating the arguments associated with creating a national  reference database. Part IV, on future directions, begins in Chapter 10 by discussing alter- native technologies to achieve the same goal as a national reference ballistic  image database. In particular, we review proposals to microstamp firearms  parts or individual pieces of ammunition with unique etched identification  codes. Chapter 11 closes the report with general guidance on the process  of developing systems for image search, retrieval, processing, and scoring,  suggesting “best practices” for development of any such program (whether  advancing current two-dimensional photography techniques or changing to  three-dimensional topography). Appendix  A  offers  additional  detail  on  the  use  of  ballistic  imaging  technology in Boston, one locale where the current NIBIN system appears  to be well used and well supported.