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Ballistic Imaging PART IV Future Directions
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Ballistic Imaging This page intentionally left blank.
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Ballistic Imaging 10 Microstamping: Alternative Technology for Tracing to Point of Sale Contemporary firearms identification and ballistic imaging techniques are predicated on the deposition of markings on evidence as a result of random variation in key processes—the manufacturing of firearms and ammunition parts and the mechanical operations and controlled explosions involved in the firing of a gun. The main objective of a national reference ballistic image database (RBID) is to use an image catalog of these markings to provide an investigative linkage between evidence collected at a crime scene and the original point of sale of the weapon. However, it may be useful to consider a completely alternative approach to arriving at the same goal: altering firearms so that, on every firing, they impart a known, unique, and unalterable marking on spent casings, rather than relying on the toolmarks generated by the firing process. If such known markings—for instance, a gun-specific alphanumeric code—are logged at the point of sale, the same goal as a national image database would be achieved: a spent casing recovered at a later crime scene could be rapidly traced back to the point of sale by reading the etched marking. Likewise, known and individual markers could be placed directly on individual pieces of ammunition; again, if the component codes in a box of ammunition are logged at the point of sale, investigative leads could result later in time when pieces of stamped ammunition are found at crime scenes. The question is whether these alternatives compare favorably to a national RBID, in terms of cost, accuracy, or time savings. This kind of technology—known as microstamping—has become a prominent part of the contemporary debate on “ballistic fingerprinting”
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Ballistic Imaging and enhancing forensic identification technology. In October 2007 legislation requiring microstamping on internal parts of new semiautomatic pistols was signed into law in California, to take effect in 2010. It is also telling that long-proposed (but never enacted) federal legislation calling for the creation of a national RBID was revised in the 109th Congress to require microstamping instead. Because microstamping has become so enmeshed in the policy debate, we describe the technology and consider its development. However, because it is not a direct task of this study, we refrain from offering formal recommendations or findings specific to microstamping. This chapter begins by describing the concept of tagging as a form of identification from a historical and technical perspective (Section 10–A) before describing current proposals for microstamping related to ballistics evidence (10–B), including the California law. Sections 10–C and 10–D focus on specific technologies for microstamping firearms parts and ammunition, respectively; brief general commentary is offered in Section 10–E. 10–A TAGGING AS A MEANS OF IDENTIFICATION Identification tagging or “labeling” crafted or manufactured items has its origins in antiquity when the first artist signed his or her work or a person wished to uniquely identify an object to reflect its point of origin, manufacture, or ownership. Unique “signatures,” either literal or representative symbols, have continued to be used for these purposes to the present day. Such markings of authorship or origin remain one of the evidentiary links used to identify art objects, for example, or to link “lost” masterpieces to their creators over the years. Over time, manufacturers transitioned from simple graphic insignia to digital serial numbers to uniquely track their goods for a variety of reasons: the increasing scale of mass production, the need for accurate sequential tracking of goods during manufacture, and the necessity of monitoring lot specificity and quality in response to legal oversight. The manner by which serial numbers are applied to objects is as varied as the products produced. Whether bar-coded, machined, cast, painted, or laser-engraved, serial numbers provide a readily discernable means to uniquely mark an object to provide provenance of an object. Because serial numbers can link manufactured objects to their owners, they provide a valuable tool to law enforcement in developing leads in criminal cases. Two well-known illustrations of the utility of serial numbers in investigating criminal cases—the bombings of the World Trade Center in New York in 1993 and of the Alfred P. Murrah federal office building in Oklahoma City in 1995—involved the use of vehicle identification numbers (VINs). A car’s VIN is roughly the automotive equivalent of human
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Ballistic Imaging DNA: although it can be altered, it generally sets a vehicle apart from the millions of other vehicles in circulation. U.S. automobile manufacturers began stamping and casting identifying numbers on cars and their parts in the mid-1950s. Originally developed to give an accurate description of the vehicle as mass production increased, the use of VINs grew in the early 1980s when the National Highway Traffic Safety Administration (NHTSA) required that all road vehicles must contain a 17-character VIN (Insurance Information Institute, 2006). The required VIN number identifies the country of manufacture, the manufacturer, the vehicle type, and specific descriptors of the individual vehicle (49 U.S.C. 565); as a unique DNA-style number for each individual vehicle, it can be used to track recalls, registrations, warranty claims, thefts, and insurance coverage. Investigators sifting through the rubble in the parking garage under the World Trade Center following the 1993 bomb explosion found fragments bearing a VIN corresponding to the number of a missing van. Tracing the van to a Ryder truck rental agency led to the arrest of a suspect in the bombing; leading in turn to the capture of additional suspects (Parachini, 2000). In the 1995 Oklahoma City case, a VIN—along with a partial license plate—were recovered at the scene of the explosion; this led to the determination that the explosive was contained in a 1993 Ford rented by Ryder in Junction City, Oklahoma. Subsequent contact with the rental agent allowed investigators to develop a composite drawing of a suspect; combined with other evidence, this was instrumental in the arrest and conviction of Timothy McVeigh for the bombing (Michel and Herbeck, 2001). In addition to the utility of unique tagging marks in furthering investigations, these examples are also illustrative in the context of firearms evidence for another reason: they suggest the remarkable retention of engraved serial numbers on metallic components subjected to explosive impact. 10–B ID TAGGING IN FIREARMS IDENTIFICATION As manufactured goods, both firearms and ammunition are already subject to conventional serial numbering. The serial number imprinted on the frame of a firearm can be traced to a point of sale if the weapon is recovered; methods for the restoration of serial numbers that have been defaced by filing or other means are an important part of forensic analysis. Similarly, boxes of ammunition also bear serial numbers, which may be useful in quality control and in identifying defective rounds. What is novel in contemporary discussion of microstamping or “ballistic ID tagging” is the potential for generating investigative leads early in the investigative process: the new technology is meant to link expended rounds of ammunition to a point of sale without requiring the recovery of the gun itself.
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Ballistic Imaging 10–B.1 Microstamping Proposals in California, 2005–2006 The idea of a large-scale reference ballistic image database became very prominent when the most populous state, California, considered the feasibility of implementing the technology. Likewise, the issue of direct tagging or microstamping of firearms and ammunition has grown in prominence due to developments in California. Microstamping had been referenced as an “intriguing alternative,” possibly an economical one, in the California Department of Justice report on a state RBID (Lockyer, 2003:6). Microstamping was also raised as a question by De Kinder (2002b:22) in his independent review of the California technical evaluation of a proposed state RBID. Subsequently, it was recommended as a research topic by De Kinder et al. (2004:215). The emerging discussion of microstamping sparked the introduction of two bills in the California legislature in spring 2005. The first bill, Assembly Bill (AB) 352, would have expanded the provisions of California’s penal code relating to handguns that are “unsafe” and hence illegal for sale. Specifically, the bill would declare as unsafe: semiautomatic pistols that are not designed or equipped with a microscopic array of characters that identify the make, model, and serial number of the pistol, etched or otherwise imprinted onto the interior surface or working parts of the pistol, and which are transferred by imprinting on each cartridge case when the firearm is fired. AB 352 passed the General Assembly in 2005 and moved to the Senate for consideration; it failed passage in the Senate in September 2005 but was made open for reconsideration.1 After a hiatus, the bill was amended in June 2006 to address some points of concern that had arisen in debate—specifically, that the “technology to create the imprint, if reliant on a patent, [must be] available to more than one manufacturer” and that the state attorney general has the authority to decide whether different methods for leaving such unique imprints on cartridge cases are “equally or more reliable and effective” and, hence, could be used for the same purpose. The bill received high-profile endorsements from the mayor and police chief of Los Angeles (Newton, 2006), as well as several county sheriffs (Sanchez, 2006), and the Senate passed its amended bill 22–18 in late August 2006. However, the Assembly and Senate could not agree on a conference version of the bill before the end of the 2006 legislative session. The second bill, Senate Bill 357, would have required all handgun ammunition manufactured or imported into California for sale or personal 1 The roll call on the vote was 20–19 in favor, but 21 votes are needed for passage in the 40-member Senate.
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Ballistic Imaging use be “serialized”—uniquely identified in a manner that permits visual inspection, in a manner so that the identifier is maintained “subsequent to the discharge of the ammunition and subsequent to the impact of the bullet”—based on standards to be prescribed by the California Department of Justice. In other words, the mark must be capable of surviving the firing of the gun and the impact of the bullet with the target. The unique identifiers on each piece of ammunition were to be coded or affixed to the box in which the ammunition is packaged. At the point of sale, then, the identifier on a box of ammunition (and all the individual identification codes contained therein) could be linked to information on the purchaser, such as name, driver’s licensee or other identification number, and date of birth. The bill required the justice department to establish a registry of ammunition vendors and manufacturers and permitted the assessment and collection of fees associated with the registration program. In addition to transmitting the sales information to the state department of justice, the bill required ammunition vendors to maintain records of sales on the premises for 7 years. The bill carved out some exemptions to the use and movement of serialized ammunition, including crime laboratories and the transfer of properties from the estate of a deceased person. Attempts to remove or obliterate identifiers on ammunition was made a criminal offense. To support the operational and administrative costs of maintaining the sales registry, the bill suggested a registration fee of $50 for handgun ammunition vendors and a user fee (not to exceed $0.005 per bullet or round of ammunition). Senate Bill 357 was passed by the Senate in June 2005 and sent to the General Assembly’s public safety committee. However, that committee referred the measure to the appropriations committee due to uncertainty regarding the costs of implementing the technology. No further action was taken on the bill during the legislative session.2 Though the California legislature did not adopt microstamping during its 2005–2006 session, it did stimulate interest in the idea elsewhere in the country; see, e.g., Tsai (2006:1) on interest expressed by New Jersey law enforcement officials in microstamping of firing pins. 2 Though the microstamping proposal was not enacted, Senate Bill 357 was in fact passed into law; in August 2006, the bill was amended to strike the entire text relating to microstamped ammunition and was replaced with language on collective bargaining with state employees.
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Ballistic Imaging 10–B.2 The California Crime Gun Identification Act of 2007 Though the ammunition microstamping bill was not revived in 2007, the firearms microstamping bill was reintroduced as AB 1471.3 Microstamping remained a high-profile issue through endorsements of the technology by local officials—at least 60 municipal police chiefs and the mayors of Los Angeles, San Diego, and San Francisco were indicated as supporters of the bill in the legislative analysis that preceded the state Senate’s vote, with 14 county sheriffs listed in opposition—as well as other reports.4 AB 1471 set January 1, 2010, as the effective date of requirements that semiautomatic pistols bear microstamped identifiers. As it developed through the legislature, the bill was amended several times. One change was cosmetic in nature, labeling the bill the “Crime Gun Identification Act of 2007,” but other amendments were substantive: The “microscopic array of characters” identifying the make, model, and serial number of the semiautomatic pistol were now required to be etched “in two or more places on the interior surface or internal working parts” of the gun, for transference to the cartridge case upon firing. The state Department of Justice is required to certify that the microstamping technology put into use “is available to more than one manufacturer unencumbered by any patent restrictions,” or to substitute methods “of equal or greater reliability and effectiveness” that are unencumbered by patent restrictions. Specific clarification was added that the microstamped identifier envisioned by the new legislation is not the same as existing identifier marks (e.g., manufacturer’s number or serial number) required by law. 3 The main content of the new bill and its 2005–2006 predecessor remained the same. However, the new AB 1471 omitted some portions of the previous legislation that explicitly required a certification program to ensure that some existing handguns meet or exceed the new standards, including the microstamping provision. 4 On May 3, 2007, the University of California, Davis, issued a press release profiling a new study from the California Policy Research Center (a center affiliated with the University of California system). The report described the performance of microstamped firing pins when fit into California Highway Patrol-issue Smith & Wesson .40 caliber pistols and fired up to 2,500 times. The study concluded that the principal markings on the stamped firing pins remained legible on repeated firings but that finer markings (e.g., striations left by a barcode etched on the side of the firing pin) were subject to wear; microstamping was said to hold promise but required further research. However, the report had not undergone review at that time, and the press release implied that the study was commissioned by the legislature and linked to AB 1471; UC Davis chancellor Larry Vanderhoef circulated a letter on May 15, 2007, to AB 1471 sponsor Mike Feuer and other legislators, apologizing for the premature release of the report and errors in the press release.
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Ballistic Imaging Having passed the General Assembly, AB 1471 was approved by the Senate on September 10, 2007 (see, e.g., Sweeney, 2007), and signed into law by California Governor Arnold Schwarzenegger on October 13, 2007. The governor’s signing measure on the bill reads:5 While I appreciate and understand that this technology is not without limitations, I am signing this bill to provide law enforcement with an additional tool for solving crimes committed with semi-automatic handguns in California. Public safety is one of the most important roles of government and I encourage all stakeholders to work on improving this technology so that it may become an even more effective crime fighting tool. 10–B.3 Proposed Federal Legislation At the federal level, the proposed Technological Resource to Assist Criminal Enforcement (TRACE) Act has been offered in the past several U.S. Congresses, but has not advanced beyond subcommittee referral. In the 109th Congress, the act was substantially revised to implement microstamping rather than a national RBID. Specifically, the proposed legislation would forbid the manufacture or import of any “firearm that is not microstamped or a microstamped firearm that does not transfer the array of characters constituting the microstamp onto the cartridge case of any ammunition fired from the firearm.” The bill, H.R. 5073, specifically defines a microstamp as “an array of characters which identify the make, model, and serial number of the firearm” that is “etched into the interior surface or internal working parts of the firearm.” Although it no longer called for creation of an image database, the new legislative text retained language from previous versions that requires “ballistics testing of any firearm in the custody of the Federal Government” and establishment of “an electronic database containing records of the results of the testing” that can be accessed by state and local law enforcement agencies. The bill was not enacted in the 109th Congress, and the same legislative text was introduced in the House of Representatives in the 110th Congress in April 2007. 10–C MICROSTAMPING OF FIREARMS PARTS The basic concept of microstamping firearms parts is to etch identifier codes into the hard metal components of guns so that—when they are fired—the markings are impressed on the relatively softer cartridge case or 5 See http://gov.ca.gov/pdf/press/2007bills/AB1471SigningMessage.pdf [accessed February 2008].
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Ballistic Imaging bullet. The early work that has been done in the area has focused on the etching of alphanumeric symbols on the tip of the firing pin. The identifying mark is created when the pin hits the primer surface of the cartridge, and the “image” of the microstamp marking can be read in the base of the firing pin impression on the recovered casing. The microstamped markings are created by ultraviolet (UV) photo-ablation by means of a high-power laser.6 As currently developed, UV radiation from an excimer laser or a frequency-tripled solid state yttrium aluminum garnet (YAG) laser is used to remove material from the firing pin tip according to a predefined pattern. The microstamp is created by illuminating the surface of the firing pin with the laser beam, either through a lithographically prepared mask or by a maskless procedure in which the beam is positioned by a system of computer-controlled movable mirrors. This latter procedure is significantly cheaper than the former. The individual symbols in the microstamped marking can range from a few microns tall to several hundred microns, with the optimum size range being 50 to 100 microns per character. A smaller size compromises the mechanical strength of the individual symbols. Due to the high intensity of the UV beam, the material is removed from the firing pin in a very short time, typically about 200 milliseconds. To increase the strength of the characters in the microstamp, a thin (1 micron) diamond or titanium carbide layer can be evaporated onto the stamp. To maintain the functionality of the firing pin, the material between the characters making up the code is removed only inside a circular area, so that the characters are raised against a background, but the character tops are flush with the original surface of the firing pin. This ensures that the overall tip shape is maintained. It also makes it much harder to remove the marking without rendering the firing pin useless. When the firing pin hits the primer, an imprint of the microstamp is left at the bottom of the impression. This imprint consists of depressions corresponding to the stamp characters or symbols. The tip of the firing pin is not the only part of a firearm that could be microstamped so that known markings are recovered on evidence fired in that weapon; however, the other possibilities remain more speculative and untested at this time. (We discuss one such idea—the etching of markings in the barrel of a gun, so that a known “barcode”-type identifier is formed on the soft bullet as it grips the rifling and exits the barrel—in Section 10–C.1, below.) Alternately, known markings could be imparted on cartridge casings by placing one or more microstamped patches on the breech block of the firearm, surrounding the firing pin hole; the mark would then be created as the soft primer surface is forced outward by the ignition of powder and 6 The process is similar to the photokeratectomy process (commonly known as LASIK) used in eye surgery to adjust the shape of the cornea.
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Ballistic Imaging expansion of gases. It may also be possible to place a microstamp identifier on the firearm’s ejector mechanism or elsewhere on the inside of the chamber (in the latter case, leaving a mark on the side of the cartridge brass). It is also reasonable to assume that, as the technology matures, multiple microstamped markings could be put on the same firearm, which would serve as a countermeasure against the defacing or attempted removal of one of the marks. However, this conceptual approach raises logistical concerns as well as technical: Would the individual markings or codes have to be identical at all places on the gun or could they be allowed to vary? The former raises potential problems in coordinating interchangeable parts with the same identifiers on the manufacturing line; the latter presents the problem of having to log all the constituent identifiers at the time of sale. 10–C.1 Research Studies In addition to experiments performed by the microstamping technology’s developer, the present technology for microstamping the tip of firing pins has been tested by two firearms examiners. Haag (2004) submitted four firing pins to the developer—NanoMark Technologies, then known as NanoVia—for microstamping: three of them were for a machine gun or automatic rifle, intended to test the durability of the microstamp engraving over large numbers of firings. In these test cases, the microstamp took the form of an eight-character alphanumeric code; firings using the treated firing pins were conducted using a mix of military and commercial cartridges that varied in primer hardness and the presence of a lacquer coat on the primer. Haag (2004) found that the marks were generally durable and left readable codes after 2,500 firings. The microstamp also left readable codes on misfired cartridges, where the pin only struck the primer lightly and the bullet was not discharged. In some instances, the presence of a red lacquer coat over the primer surface—which might be hypothesized to absorb impact and degrade the markings left on the primer—actually served to accentuate the alphanumeric code. The fourth firing pin submitted for microstamping was from a Glock pistol, and was so chosen due to the distinctive scraping (and resulting scrape mark) known to occur in the firearm; this provided the opportunity to test the durability of the stamp given the additional wear caused by scraping. A variety of ammunition was run through the Glock with the microstamped pin, including lacquered primers and casings with pronounced nonfiring manufacturing marks. After more than 1,400 rounds, Haag (2004) concluded that the firing pin scrape in the Glock did not degrade the microstamped identifier and that neither lacquered primers nor variation in primer finish and hardness affected the microstamp’s ability to impart a fixed marking.
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Ballistic Imaging However, Krivosta (2006) offered cautionary notes based on work with microstamped barrels prepared at the request of the Rhode Island Crime Laboratory. He observed that “a number of test fires” from a Remington .22 Long Rifle semiautomatic rifle—a rimfire weapon, rather than centerfire—were “illegible.” The microstamped marking did not register well in the hard brass of the cartridge rim, and marks were further obscured by repeated (and overlapping) strikes of the pin against the cartridge during the same firing sequence (Krivosta, 2006:42). He also questioned the explicit provision in then-proposed state legislation that the microstamped identifier on firearms include the gun’s make, model, and serial number—a large number of characters for a small surface area. Specifically, he referred to firings involving two Colt .45 pistols with different microstamp configurations—one with an eight-character alphanumeric code in “large,” block capital letters and the other showing the name “NanoTag™” surrounded by the digits 0–9 and the full English alphabet in smaller “type.” With the latter microstamped engraving, “the vast majority of this pin’s characters were never visualized in the firing pin mark of any of the [ten] expended cartridge cases generated and examined” (Krivosta, 2006:42). Krivosta (2006:43) subjected a microstamped firing pin to “intentional defacement:” a process “easily accomplished in approximately one minute’s time” using a sharpening stone and a portable drill. The removal of the microstamped identifier in this case did not impede the ability of the gun to fire: the mechanics of the gun are such that “the pin could have easily been shortened by 0.030 inch or more … and the weapon would have still functioned.” Although much of the initial work done to date has focused on placing microstamped identifiers on firing pins (thus marking cartridge casings), parallel work has continued on placing known identifiers on other parts of the firearm. In particular, Carr and Fadal (1997) and Fadal and Nuñez (2003, 2006) describe efforts by one manufacturer, Glock, to develop an alternative rifling technique to impart “readily identifiable” marks on bullets as they pass through the barrel. The introduction of such a technique is particularly significant since Glock’s use of polygonal rifling has traditionally made bullets extremely difficult to match in the past. The work was initiated through a special order by the Miami Police Department, and so the efforts are described in the literature as “the Miami barrel”; Glock has also referred to the modified barrels as the Enhanced Bullet Identification System, or EBIS.7 7 The “Miami barrel” followed another Glock experimental effort, the “New York barrel”; under a special order from the New York City Police Department, Glock produced a set of barrels for testing using conventional rifling rather than the company’s usual hammer-forged hexagonal rifling (Carr and Fadal, 1997:233).
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Ballistic Imaging Fadal and Nuñez (2006:98) cite Glock as stipulating that “their patented tooling method may be manipulated to create 80,000 possible different combinations per caliber,” using a “finger-like tool” to etch cuts in the barrel wall. The markings intended to be replicated with every firing by the Miami barrels include both gross characteristics that may appear the same across guns (subclass characteristics) and fine individual detail. Up to 3,000 rounds were fired through the latest iterations of the Miami barrel; “the gross and individual characteristics changed slightly between test firings as may be expected with wear (e.g., test from 500th shot as compared to test from 2000th shot),” and test bullets were still distinguishable after 3,000 firings (Fadal and Nuñez, 2006:97). 10–C.2 Advantages Conceptually, the microstamping of firearms parts so that a known, unique, and repeatable identification tag is imparted on each cartridge case (or bullet) passing through a weapon has several potential advantages for forensic identification. Assuming that the microstamped identifier is clearly impressed on spent casings, no special equipment is needed to read the identifier code; it can be viewed using microscopes already present in standard laboratories. Conceivably, some identifiers could even be read at crime scenes using a hand magnifying lens, saving considerable time. Again assuming a clear impression, identification based on a microstamped marker is also easier to explain and interpret, as it does not require the subjective judgment that is now central to the interpretation of toolmarks left on a spent cartridge case. The fixtures used to hold and manipulate the various firearms components during the etching of the microstamp would be specialized equipment, but the machinery used to perform the etching is not highly specialized. To the extent that microstamping is performed on modular parts of a firearm—for instance, on firing pins that are manufactured and tooled independent of other parts and then assembled on the production line—the process need not be disruptive of the whole firearms production cycle. Also, each individual imprint can be created in a short time—typically around 200 milliseconds—so that the additional overhead in the firearms production process is small. More than one microstamped identifier could be placed on different areas of the gun’s firing assembly to increase the likelihood that at least one identifiable mark will be imparted on cartridge case or bullet evidence and recoverable by investigators. As noted above, though, multiple identifiers raise the issue of coordination, ensuring either that the same identifier
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Ballistic Imaging is placed on all parts in the same gun or that all the individual identifiers are cataloged and linked to the same gun. Placing recessed characters on the firing pin, and perhaps adding a microstamped identifier elsewhere, would make it more difficult to deface or remove the identifiers without rendering the gun inoperable. As observed by Haag (2004), microstamped identifiers on firing pins appear to work in some instances where difficulty would naturally be expected, such as ammunition with lacquered primers or misfired cartridges. In the latter example, though, the markings may require more advanced equipment and microscopy to read the marking. Microstamping of firearms parts is akin to—and can be perceived as an extension of—the known and accepted practices of placing a serial number on all guns sold in the United States and logging that serial number at the time of sale. 10–C.3 Disadvantages There are also important conceptual disadvantages of microstamping firearms parts, particularly the firing pin. Firearms microstamping shares a critical liability of an RBID: Barring a radical (and likely untenable) legislative requirement prohibiting use of any firearm without a microstamped identifier, the coverage of firearms microstamping would include only new firearms. Hence, the millions of firearms currently in circulation would not be affected. Thus, a resource such as the existing NIBIN database would still be necessary to assist examiners with finding links to crime guns that come from the existing stock of guns. Like a national RBID—for which the focus would likely be on cartridge casings rather than bullets, due to the time necessary for nondestructive test firings to obtain bullet specimens—microstamping strategies that only impart identifiers on cartridge casings would not be effective in solving crimes involving revolvers. Similarly, such strategies would also be hindered in instances in which suspects remove spent casings from crime scenes. Firing pins can be replaced with relative ease, so a single microstamped identifier could be defeated by swapping in a new pin. Working around this would require that newly manufactured firearms parts have to bear an identifier, and that this information would have to be logged at time of sale and maintained on file. Estimates of the per-unit cost to place a microstamp tag vary widely. Proponents of microstamping suggest that the cost of marking a firing pin would be between $0.50 and $1.00 (Tsai, 2006), with some
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Ballistic Imaging estimates as low as $0.15. However, opponents claim the cost to be closer to $150 (Tsai, 2006), perhaps taking into account the initial capitalization needed to obtain and operate the equipment or to change production flows so that component parts are stamped. As discussed by Krivosta (2006), microstamped identifiers may be difficult to use effectively in rimfire weapons and in low-pressure firings. A database associating microstamped identifier codes with purchase information would need to be constructed. Populating this database would require coordination at the federal and state levels to manage input from individual firearms dealers. Politically—as is the case with a national RBID—the question of whether information on the purchaser, and not just the point of sale, should be logged in the database would have to be addressed. Although the task of setting up and maintaining such a database would not be exceptionally difficult, it would still be a large database and would take resources to manage, purge, secure, upgrade, and operate. However, it is worth noting that this database would avoid some costs associated with a large-scale RBID, such as the manpower requirements to acquire images and the storage and preservation of physical exhibits. 10–D MICROSTAMPING OF AMMUNITION As described above, the microstamping of firearms—as currently conceived—is principally about imposing marks on expended cartridge casings. Hence, as would be true in a cartridge case-only national RBID, it would not work in settings in which casings are not expelled at crime scenes (e.g., revolvers are used) or are removed from the scene. A different approach to microstamping focuses on bullets. Conceptually, the microengraving of individual markers on every bullet offers one prominent advantage over other identification technologies, which is that—in time—it would aid in criminal investigations involving guns that are already in circulation. Ammunition can be a durable commodity but it is, ultimately, exhaustible, and new (microstamped) ammunition would eventually replace it. 10–D.1 Ammunition Microstamping Process There are multiple points in a single ammunition cartridge that could, conceivably, be engraved using microstamping. However, as experienced in the analysis of bullet striations, the sides of a (relatively soft) bullet can warp or distort on impact, and fragmentation of the bullet is also possible. In what follows, we outline the approach that was advocated by Ammunition Coding System (ACS), the firm (and prospective vendor) that was the focus of attention during debate on the California microstamping legislation.
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Ballistic Imaging For maximum survivability, the ACS proposal centers on the etching of microstamped identifiers on the base of the bullet. In initial work, the identifier is a six-character alphanumeric code. The code is not engraved a single time on the base but, rather, repeated several times, in an array over the surface of the bullet base. The goal of this repetition is to “allow law enforcement personnel to identify the bullet code in cases where as little as 20% of the bullet base remains intact after recovery” (http://www.ammocoding.com [February 2008]). Though placing the marker on the base of the bullet may enhance its survivability, it does raise a basic logistical and physical problem at the time of manufacture: the base of a bullet is no longer visible once the bullet is seated in the cartridge. Hence, the assembly line process for bullets must be reengineered so that—at a minimum—the code etched on the bullet in a single cartridge is known when that cartridge is put in a box or that the same code is etched later in the process on a visible part of the cartridge (e.g., the side of the bullet or the exterior of the cartridge case). This concern is addressed in part by the etching of the identifier, once, on the surface of the bullet near the tip. In addition, ACS prototyped a process wherein a camera records the code marking on the bullet base immediately prior to its being seated in the cartridge; based on the camera reading, the assembled cartridge is cycled through additional machinery so that the same code on the bullet is etched on or near the bottom of the cartridge case. (As a late-in-the-stage process, care is obviously required in devising this process and creating the printed code since the propellant and primer would already be in place in the cartridge.) Once marked, the rounds are packed in a cardboard box; a scanner would then read the codes on all the individual rounds in the box and generate a barcode label to be placed on the box. This single, exterior barcode would then be scanned at the time of retail purchase. Later, when a microstamped bullet is recovered at a crime scene, the individual bullet code would be read and matched to an exterior box code; that box code would in turn provide the lead to the point of sale. ACS-marked ammunition was subjected to two tests by California law enforcement personnel. In April 2004 the San Bernardino County Sheriff’s Department test fired 25 rounds of microstamped ammunition, including both .45 caliber and 9mm ammunition, firing into media including plywood, rubber, and a steel door. Three of the bullets were unrecoverable; of the 22 that were recovered, an identifier code could be read on 21.8 The California Department of Justice conducted further testing on 200 rounds of microstamped ammunition in September 2004. In addition to firings 8 The exception was a 9mm round fired from 25 yards into 1.5 inches of rubber; only two small fragments could be recovered, but apparently not enough of the base endured in order to preserve the code.
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Ballistic Imaging into the side of a car door and standard wall material (plywood, insulation, and drywall), rounds were fired into gelatin to replicate the consistency of human bodies. When the bullet was recoverable—in 181 of the 200 firings—the code was again readable in all but one instance.9 10–D.2 Advantages There are at least five advantages to microstamping ammunition. Fully implemented, microstamped ammunition can provide valuable investigative leads from evidence recovered at crime scenes to the point of sale, and perhaps to the original purchaser. As described at the beginning of this section, a key conceptual advantage of ammunition microstamping is that it would, eventually, be applicable to the existing gun stock. Though ammunition may be stockpiled and can be durable with proper storage, it is possible that much of the existing ammunition stock would turn over in 3–5 years, and that new (microstamped) ammunition would gradually replace it. Microstamping ammunition overcomes a limitation of a national RBID based on cartridge case evidence, in that bullets are almost always “left” at a crime scene. The base of a bullet—the proposed area for the microstamped identifiers to be located—is more likely to avoid warping or deformation when the bullet hits a target, relative to the striation marks on the side of the bullet. The process of reading a code on a recovered bullet is a relatively quick one, and in some cases may be possible at the crime scene itself. The key time limitation would be in extracting the bullets from wherever they may be lodged. As with marks from microstamped firearms parts, the identifiers can be read without specialized training or equipment. 10–D.3 Disadvantages There are also significant disadvantages to microstamping ammunition. Although markings on the base of a bullet have proved to be durable in testing in some highly demanding situations—firing into wood or a car door, for example—the durability and survivability of markings on the bullet are still major concerns. Bullets would also be likely to suffer 9 The exception occurred in firings of 30 rounds of .38 Special ammunition into a car door from 10 yards: 22 of the 30 bullets were recoverable, and it was one of these bullets that was unreadable.
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Ballistic Imaging the corrosive effects of blood and other substances (and the potential for damage in cleaning them). The investigative lead generated by recovering a microstamped bullet from a crime scene would be between a crime-related bullet and its purchaser; as is true with a national RBID, this stops short of directly linking ballistics evidence to the particular person who fired the shot. Moreover, in complex crime scenes where multiple firearms are discharged, microstamped bullet markings could not directly lead to connections between specific bullets and the guns that fired them. Though individual records would be much simpler than in an image database, ammunition microstamping would require a new database of massive scope, providing the mapping from codes on individual rounds of ammunition to the code on the box of ammunition that contained them. This new database would rely on collection from ammunition manufacturers and would grow by billions of records (one per piece of ammunition) each year. In the discussion of ammunition microstamping in California, a perceived advantage was that the second critical data-gathering activity—logging the ammunition box codes at the point of sale—would require little or no new resources. Because the technical infrastructure to scan both ammunition-box barcodes and the barcodes on purchasers’ driver’s licenses is already in place among the state’s ammunition vendors. However, in other states, barcode reading and ammunition sales databases may not be standard, and practices for examining or recording driver’s license or firearm owner’s identification card information may also vary. In such states, a new system would have to be developed to capture codes at the point of sale. As is the case with firearms microstamping, cost estimates vary widely, and the inability to peg down a per-unit cost factored into the inability to pass the California legislation. In terms of initial capital costs to ammunition manufacturers, Ammunition Coding System stipulated that “reliable estimates for a complete set of engraving/material handling equipment range from $300,000 to $500,000 each.” However, “since approximately 10 billion bullets are sold in the United States alone each year, equipment costs, once amortized over the number of bullets produced and sold are not significant” (http://www.ammocoding.com [February 2008]). While proponents of microstamping argued that the per-bullet cost would amount to 1 cent or less, ammunition manufacturers countered that the per-unit cost would be measured in dollars (Yamamura, 2005b). A further sticking point in the California legislation was the provision for a licensing fee—per round of ammunition—to be paid, in addition to the cost of making the laser engravings. Research on the costs associated with retooling existing manufacturing plants would have to be conducted as a supplement
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Ballistic Imaging to implementation estimates being offered by vendors. The per-round costs were raised as a particular concern for high-volume ammunition purchasers such as police forces (Yamamura, 2005a) and the military. The proposed laser marking proposed by Ammunition Coding System involves evaporation of lead, as well as laser marking on live ammunition and the use of lasers where explosive compounds are present. Extensive research would be required to resolve environmental and safety concerns. 10–E COMMENTARY It is not within the committee’s purview to offer formal recommendations on microstamping technologies—to suggest microstamping as a more reliable, less expensive, or generally better alternative than imaging technologies applied to ballistics evidence, or vice versa. However, we find that both the microstamping of firearms parts and ammunition possess the formidable conceptual advantage of imposing discernible and objective uniqueness on bullet or cartridge case evidence. Thus, microstamping could provide a stronger basis for identification based on the evidence than the status quo, positing that uniqueness arises from random microscopic phenomena and assuming that unique features manifest themselves in different imaging media. However, it is also abundantly clear that substantial further research would be necessary to inform a thorough assessment of the viability of microstamping either gun parts or bullets. Particularly necessary would be credible estimates of the real cost of implementation, separating initial configuration costs from other life-cycle costs, that accurately take into account the reengineering of existing firearms and ammunition production lines. The emergence of microstamping suggests a theme that we explore further in the next chapter. In microstamping—as in the early days of computer-based ballistic imaging—there has arguably been a push to legislate on the basis of the claims and competences of one or two vendors. We do not challenge the work done by the vendors who have suggested microstamping to date; they have made solid and worthwhile contributions. Microstamping may indeed be a viable future for firearms identification, and we strongly encourage continuing research in this area. However, we do conclude that state and federal law enforcement would be better served by new technologies and systems developed through richer and more open competitions, by multiple vendors and research teams and with fuller appreciation for the integration of new systems with existing manufacturing practices.