Body Armor Information Summary of Technical Aspects by Julius Chang (p00302@psilink.com) * Intro * How soft armor works and a description of Kevlar and Spectra * Description of the (National Institute of Justice) NIJ 0101.03 body armor standard * OTA suggestions on changes to the .03 standard Recommended Citation: U.S. Congress, Office of Technology Assessment, Police Body Armor Standards and Testing: Volume I, OTA-ISC-534 (Washington, DC: U.S. Government Printing Office, August 1992). INTRODUCTION Every year, about 60 sworn police officers are shot to death in the line of duty (1, 2). At the same time, about 20 are saved by wearing armor. Had all the officers shot in recent years been wearing armor when shot, another 15 per year would likely have been saved from fatal gunshot wounds, roughly doubling the present number saved, and more than 15 others would likely have been saved from death by other causes (3). Most police officers serving large jurisdictions report they have armor and wear it at all times when on duty and clearly identifiable as police officers [102]. The kind of armor usually worn is soft armor, which is designed to be concealable -- most styles are undergarments -- and comfortable enough to be worn routinely. Such armor is designed for protection from handgun bullets but not from rifle bullets or edged or pointed weapons such as knives or icepicks. The distinctive, nonconcealable "tactical" armor worn by police SWAT (Special Weapons and Tactics) teams for protection from rifle bullets as well as pistol bullets is more familiar to many laymen. Garments of both types are sometimes called "bulletproof vests," but no garment will *certainly* stop any bullet. Indeed, there is no guarantee that a bullet of a type a garment is designed to stop will not kill a wearer. Much of the body is not covered by the protective panels of a particular armor: an asute purchaser may choose a model from the many on the market, fully aware of that coverage limitation. However, the *ability of armor to stop bullets -- its "ballistic resistance" -- cannot be discerned by inspection; it must be inferred from the results of tests in which sample armor is shot.* Because such testing is destructive, vests slated for marketing are not tested. Moreover, the conditions under which an officer is shot are unlikely to be identical to test conditions. In 1972, in an effort to provide police departments guidance in such testing, the National Institute of Law Enforcement and Criminal Justice (NILECJ), a part of the Department of Justice, issued a standard for ballistic resistance of police body armor, NILECJ Standard 0101.00. It specified general procedures and specific types of bullets and velocities to be used in tests to determine whether samples of armor had certain types of ballistic resistance defined in the standard. It was a voluntary performance standard -- i.e., armor could be sold without meeting the standard, but if it were tested and passed, the manufacturer could certify this on the label. Armor made from any type of material could, if thick enough, meed the standard. The .00 standard specified a reproducible but arbitrary ballistic test, uncorrelated with physiological protection: There was no attempt to correlate penetration in the test with risk of penetration in service, and it did not attempt to gauge protection from injury by stopped bullets. NILECJ Standard 0101.00 has been superseded thrice: by NILECJ Standard 0101.01 in 1978, by NIJ (National Institute of Justice) Standard 0101.02 in 1985, and by NIJ Standard 0101.03, the current standard, in 1987. The .01 standard was the first to be based on a quantitative safety criterion and biomedical experiments (shootings of animals) intended to demonstrate that samples of armor *like those passing the test* would perform as required in service. The current method, like its predecessors, is necessarily the result of an implicit trade-off among simplicity, economy, realism, reproducibility, risk to the consumer, and risk to the producer (4). For example, a wide variety of bullets impact at unknown velocities in assaults, but, in the interest of reproducibility, the test requires particular types of bullets to be fired at velocities varying by no more than 50 feet per second. Each revision had its proponents and its critics, but the latest revision evoked unusual controversy when "NIJ funded the retesting of all models tested under the .02 program. However, less than half -- 34 out of 84 -- of models tested passed under the new standard." (5)[151] This surprised NIJ as well as those in industry who had been consulted about the revision. A DuPont spokesman later claimed, "Both sides [NIJ and the Personal Protective Armor Association (PPAA), an industry group] agreed '03' was to be no more stringent than '02.'" [13] The PPAA devised its own standard, PPAA Standard 1989-05, which is demonstrably less stringent but also, the PPAA argues, more realistic and reproducible (i.e., results of similar tests are more likely to be similar). Many purchasers, prospective purchasers, and wearers of body armor have been confused by the controversy, and some manufacturers attribute a decline in sales to the confusion. Critics of the NIJ standard, including some manufacturers of armor material and garments, point to the large fraction of .02-certified models failing the .03 test as evidence of excessive stringency of the .03 test. They point to the mixed results of .03 tests of samples of the same model (sometimes labeled as different models) as evidence that the .03 test yields "inconsistent" results; some critics have called the test "a crap shoot." They question the rationale for crucial aspects of the standard, such as a test intended to gauge protection against serious or lethal blunt trauma (bruising or tearing of internal organs) that could be caused by the impact of a bullet stopped by the armor. They charge that the conservatism of the standard and the variability of test results induce manufacturers to make armor that is heavier, stiffer, less comfortable, and more costly than is necessary to provide the nominal protection certified. Most importantly, they charge that excessive cost reduces sales, and excessive discomfort reduces wearing, of certified armor, with the result that officers who could have been saved by good uncertified armor (or armor certified to comply with a less stringent standard) have been killed not wearing it: "Police officers are not dying in defective body armor. Police officers are dying because they are not wearing body armor!!" [15] They also believe that the standards controversy itself reduces the sales and wearing of good armor. Defenders of the NIJ standard, also including some manufacturers of armor material and garments, believe that the standard's testing requirements and procedures are warranted by the ballistic threats facing police officers and rebut arguments for changing it. They claim the PPAA standard is not stringent enough. They ascribe variation in test results to variation in vest construction. Gross variation in the construction of supposedly identical vests -- such as differing numbers of fabric layers -- can be seen in the archives of NIJ's Technology Assessment Program Information Center (TAPIC). A legislative remedy to the controversy has been attempted twice: Two identical bills introduced in the 101st Congress, H.R. 4830 and S. 2639, would, if enacted, have made it a criminal offense to manufacture, distribute, or sell armor not complying with NIJ Standard 0101.01, or any superseding standard issued by NIJ. H.R. 322, a bill introduced in the current (102nd) Congress, contains the same language. This report of OTA's assessment of police body armor standards and testing was requested by Senator Joseph R. Biden, Jr. (Chairman), Senator Strom Thurmond (Ranking Minority Member), Senator Dennis DeConcini, and Senator Edward M. Kennedy of the Senate Committee on the Judiciary, Congressman John Joseph Moakley, Chairman of the House Rules Committee, and Congressman Edward F. Feighan of the House Committee on the Judiciary and of its Subcommittee on Crime and on Economic and Commercial Law. The purpose of the study was to clarify the issues of whether NIJ Standard 0101.03 should be revised and if so, what actions Congress might take. Congress would like to know wheter the standard is informative and fair to purchasers and wearers or armor, as well as to manufacturers of armor and its component materials. Purchasers and wearers need to know how confident they can be that certified armor will protect them or to what degree uncertified armor will be less protective. Manufacturersare justified in demanding that the standard not discriminate unfairly against their products. Principal points of uncertainly are: how confident wearers can be that samples of a model, other samples of which have passed the test, will protect them in the line of duty (and under what circumstances); how confident manufacturers can be that testing more samples of the same model would yield similar results; how confident prospective purchasers can be that they won't be defrauded; and whether performance charactersitics of dubious value are being tested. Specific points of contention include the following: * Whether armor must be tested wet (as well as dry), as the standard specifies. * Whether armor may be patted down between test shots (which the standard prohibits) to reduce the ply separation ("bunching") caused by previous shots. * The incidence and statistical significance of apparently random variations in outcomes of similar tests, and if significant, their causes. * Whether armor should be failed (as the standard requires) if a nonpenetrating test shot makes a crater deeper than 44 mm (1.73 in) in the material on which the armor is mounted; this is assumed to indicate inadequate protection from the impact of a stopped bullet. * The protection afforded by the current standard against false or deceptive advertising or labeling (e.g., of armor as complying with the NIJ standard, when in fact it has not been tested for compliance). In addition, the study was to investigate ancillary issues, such as the shape of the test fixture to which the armor is attached for ballistic-resistance testing and the choice of the backing material (inside the test fixture) against which the armor is placed to be shot. FOOTNOTES 1. Most lethal shootings are felonious; a few are accidental. 2. Many unsworn police officers, such as private security guards, are also shot to death. 3. See Findings, below. 4. The rationale for each revision is discussed in detail in appendix A of this report. 5. Those involved have later pointed out that the poor record-keeping of the .02 era precludes definite knowledge of which vests passed, or indeed of which were tested. The issue is further clouded by the fact that NIJ permitted the manufacturers of vests to resubmit them under different designations, and even to submit totally different vests. The Government felt the change from .02 to .03 obliged them to offer a free test, but the manufacturers chould choose what vest to test. REFERENCES 13. Bachner, [Thomas E.] Ed, "The History of NIJ's Test Problems," section 9 of The DuPont Mid-West Body Armor Symposium, sponsored by Missouri Police Chiefs, Inc., and the International Association of Chiefs of Police, Chesterfield, Missouri, August 29-31, 1990 (Wilmington, DE: The DuPont Company, 1990). 15. Bachner, Thomas E. (ed) Jr., Brierly, William, and Slavin, Helen A., "Casualties vs. Casualty Reduction -- Lessons Learned From the Eighties," section 7 of The DuPont Mid-West Body Armor Symposium, sponsored by Missouri Police Chiefs, Inc., and the International Association of Chiefs of Police, Chesterfield, Missouri, August 29-31, 1990 (Wilmington, DE: The DuPont Company, 1990). 102. Michaels, Maureen (Strategy Polling Corporation), Rowan, Michael (Strategy Polling Corporation), and Curran, Jim (John Jay College of Criminal Justice), National Body Armor Survey (New York, NY: City University of New York, John Jay College of Criminal Justice, March 1991). 151. U.S. Department of Justice, Office of Justice Programs, National Institute of Justice, Office of the Director, The NIJ Body Armor Program, enclosed with letter of Charles B. DeWitt (Director, NIJ) to Michael B. Callaham (Senior Analyst, OTA), July 30, 1991. Box A -- How Soft Armor Works Soft body armor works by catching the bullet in a net-like web of very strong fibers. The bullet stretches not only the few fibers it hits, but also others in contact with them and many more that those pull. As in any net, the key to success is that many fibers, even those not actually touching the bullet, elongate in response to the collision and so absorb the energy of the bullet. Even so, materials available today do not permit the construction of a vest from a single ply of fabric -- a number of layers, often about one or two dozen, are needed to stop a bullet. Soft armor has been made from a variety of natural, and more recently, synthetic fibers. For example, silk, which had been used for armor in medieval Japan, was used in American ballistic (bullet-resistant) armor late in the nineteenth century. It attracted Congressional attention after Presiden William McKinley was assassinated in 1901, and was said to have been worn by Archduke Francis Ferdinand of Austria when he was killed by a shot in the head, which precipitated World War I. Although it provided some protection against handgun bullets at low velocity (e.g., .40-caliber lead or .45-caliber jacketed at 400 feet per second), it could not stop higher velocity handgun bullets (e.g., .45-caliber jacketed at 600 feet per second), much less rifle bullets. This shortcoming, together with the expense of silk (then about $80 per garment), made silk armor unattractive to the U.S. Ordnance Department in World War I. [53] The tensile-strength-to-weight ratio ("tenacity") of silk -- no more than about 5 grams per denier [89] -- was surpassed by synthetic fibers such as nylon (8 g/d) and, later, Kevlar(R) (26 g/d) and Spectra(TM) (35 g/d). Some spider silk has even greater tenacity, [162] but it cannot be cultivated and collected economically as silkworm silk can. Genetic engineers are striving to develop a way to copy it. During the Second World War and the conflict in Korea, the United States Army developed soft armor made of nylon. These vests provided considerable protection, but were very bulky. Concealable soft body armor as we know it today was made possible in the mid-1960s, when a solvent for polyaramid plastic was discovered; this permitted the production ("spinning") of polyaramid fiber (see Box B). Polyaramid fibers have higher tenacity than nylon does, and less elongation before breaking than silk or nylon. The first soft body armor for police use, however, was of nylon. Richard C. Davis holds several patents relating to police body armor [47, 48, 49, 50] including one [47] for a small, light nylon vest designed to protect the wearer's vital organs from the short-barreled, medium-caliber handguns known as "Saturday night specials." The application for this patent was filed on May 8, 1972. Today, several types of polyaramid fiber are marked under the names Kevlar(R) (by the DuPont de Nemours co., Inc.) and Twaron(R) (by Akzo, Inc.). This fiber is woven into fabric by weavers (two or three produce most of the U.S. ballistic fabric), and the fabric is used in the construction of vests by several U.S. and foreign manufacturers. The first "save" credited to Kevlar(R) occurred in 1973. More recently, soft armor has been made from fibers of extended-chain polyethylene (ECPE). Produced by Allied-Signal, Inc., the fiber, marketed as Spectra(TM), has greater tenacity and slightly less elongation than Kevlar(TM). Although, some Spectra(TM) fiber is woven into Spectra(TM) fabric for armor, Spectra(TM) is also used by Allied-Signal in the manufacture of Spectra-Shield(R), a nonwoven composite material used in soft as well as rigid armor (see Box C). A single, thin flexible sheet of Spectra Shield(R) is made by (1) bonding a single layer of closely spaced parallel fibers together with Kraton(TM) resin (produced by Shell Chemical) to form a single ply, (2) bonding two such plies together, one rotated 90 degrees from the other, and (3) coating each surface of the two-ply sheet with a film to reduce friction and abrasion. Several such sheets are required to provide protection from handgun bullets. Spectra Shield(R) was first sold to body armor manufacturers in 1988. Some manufacturers make "hybrid" armor by sandwiching sheets of Spectra Shield(R) between layers of Spectra(TM) or Kevlar(R) fabric. Untreated fabric woven from either polyaramid or ECPE fiber loses some ballistic performance when it is wet. Possibly the water lubricates the intersections of the weave, so that stretching fibers slip on their neighbors rather than pulling them into sharing the work of stopping the bullet. There are three options for preventing or reducing this effect: * The fiber or fabric may be treated by any of several processes to promote water-repellency. * Armor panels of untreated fabric may be encased in waterproof covers. * Armor panels may use enough untreated fabric to provide the ballistic resistance desired even when wet. Upon drying, untreated fabric of either type regains its original ballistic performance. The ballistic resistance of panels of Spectra Shield(R) non-woven composite material is unaffected by wetness. Box B -- Kevlar(R) and Twaron(R) Kevlar(R) is strong fiber made from polymeric aromatic amide (polyaramid) plastic by dissolving it in a special solvent and spraying the solution through a small nozzle called a spinnerette. The solvent evaporates, leaving the plastic fiber, which has a strength-to-weight ratio about five times that of steel. The possibility of making polyaramid plastic was hypothesized in 1939. It was synthesized and identified at DuPont in 1960, but polyaramid fiber could not be produced until 1965, when Stephanie Kwolek, a chemist at DuPont, discovered a practical solvent. At about the same time, a team at Akzo, Inc., a multinational firm headquartered in Holland, independently discovered a practical solvent and applied for a patent for the manufacture of polyaramid fiber, which DuPont named Kevlar(R) and Akzo later (1984) named Twaron(R). DuPont contested the patent. A consent decree of the International Trade Commission settled the dispute; terms of the settlement included cross-licensing but barred Akzo from marketing Twaron(R) in the United States until late 1990. Before Kevlar(R) was used for body armor, it was used as a substitute for steel in the manufacture of radial tires, including those designed for police cars. it does not melt but does pyrolyze (decompose) at very high temperature. It loses some strength as its temperature is increased but remains strong enough to be used for applications requiring high strength-to-weight ratio at high temperature -- e.g., in the telescoping nozzles of solid-fuel rocket motors of the Peacekeeper (formerly MX) missile. "Kevlar" is a registered trademark of DuPont de Nemours and Co., Inc. "Twaron" is a registered trademark of Akzo, Inc. Box C -- Spectra(R) and Spectra Shield(TM) Spectra(R) is a registered trademark of Allied-Signal, Inc., for the high-strength synthetic fibers the company produces from extended-chain polyethylen (ECPE). Key properties of these fibers (marketed under the brand name Spectra 1000) include low weight and high strength, as well as resistance to impact, moisturem, abrasion, chemicals, and puncture. The first successful commercial application for Spectra fibers, introduced in 1985, was as a substitute for steel in ropes and cordage. Other applications that followed include puncture- and cut-resistant safety gloves. For soft body armor applications, Spectra fibers are woven into bullet-resistant fabrics or, more commonly, used as a reinforcing fiber in a flexible, nonwoven composite material called Spectra Shield(TM), introduced in 1988. Thicker, rigid Spectra Shield (TM) is also made for use as hard armor in helmets, radomes (protective coverings for radar antennas), sonar, and other applications. Spectra fibers are made by a process called gel-spinning. Extended-chain polyethylene molecules containing 70,000 to 350,000 carbon atoms are dissolved in a solvent which is heated and forced through tiny nozzles called spinnerets. The resulting jets of solution cool and harden into plastic fibers, which are drawn, dried, and wound onto spools for further steps in manufacturing. This fiber-producing process aligns the extended-chain polyethylene molecules so that the hydrogen atoms of each molecule bond with those of its neighbors. This gives Spectra(R) a tensile strength greater than aramid fibers. Spectra(R) is also less dense than other fibers; its specific gravity is only 0.97, so it floats. Pound for pound, it is 10 times as strong as steel. Spectra Shield(TM) is made by aligning Spectra(R) fibers side by side and bonding them with a flexible Kraton resin (produced by Shell Chemical) to make a single-ply sheet. Two plies of such seets are crossed, so that the fibers in one are perpendicular to the fibers in the other, and bonded together. The resulting 2-ply, cross-plied sheet is coated on each side with an abrasion-resistant film to make one thin, flexible sheet of two-ply Spectra Shield(TM) composite material for use in body armor.[4](1) Thicker, multi-ply panels for use as structuralk armor are made by cross-plying additional layers before coating. A ballistic panel for an armor garment could be made by cutting multiple layers of two-ply Spectra Shield(TM) into the desired shape, stacking them up like pancakes without stitching them together, and enclosing them in a cloth cover. The cover need not be waterproof, because Spectra Shield(TM) is highly water-resistant. Exposure to water has no effect on its ballistic resistance. Spectra Shield(TM) is also highly resistant to degradaton by chemicals such as household bleach. Another notable characteristic of Spectra Shield(TM) is the high velocity -- 12,300 m/s -- at which the stress imparted by a bullet propagates within the armor outward from the point of impact, which allows the bullet's energy to be absorbed by a large area of the armor. In the 1 to 2 milliseconds during which a low-energy bullet is decelerated by armor and backing material, [100] part of its energy would be distributed over and absorbed by the entire ballistic panel. Spectra(R) fabric and Spectra Shield(TM) can be ignited but only when their temperature reaches 675 F; they are less flammable than cotton or polyester fabrics typically used for police uniforms. Flame-retardant tactical armor has been made by enclosing Spectra Shiled(TM) in a carrier garment made of flame-retardant fabric. Spectra(R) melts at a temperature of 160 F. Armor so hot would be excruciatingly painful and would burn skim in less than a second, [128] so ballistic resistance at so high a temperature is almost irrelevant. Spectra Shield(R) stored for 90 dyas at 160 F and then allowed to cool to room temperature regained its room-temperature ballistic resistance.(2) FOOTNOTES 1. See also Gary A. Harpell et al., "Ballistic Resistant Composite Article," U.S. Patent 4,623,574, Nov. 18, 1986. 2. Viz., V50 measured per MIL-STD-662D using a .22-cal., 17-gr fragment-simulating projectile. REFERENCES 4. "Biting the Bullet: New Nonwoven Finding Application in Ballistic Protection," Nonwovens Industry, April 1991, pp. 28 & 30. 47. Davis, Richard C. (Inventor), "Bullet Proof Protective Armor and Method of Making Same," U.S. Patent 3,783,449, 8 Jan. 1974 (filed 8 May 1972). 48. Davis, Richard C. (Inventor), "Bullet Proof Protective Armor," U.S. Patent 3, 829,899, 20 Aug. 1974 (filed 31 Oct. 1973). 49. Davis, Richard C. (Inventor), "Bullet Resistant Under Garment," U.S. Patent 3,855,632, 24 Dec. 1974 (filed 7 Jan. 1974). 50. Davis, Richard C. (Inventor), "Bullet Proof Protective Armor," U.S. Patent 3,894,472, 15 July 1975 (filed 8 Aug. 1973). 53. Dean, Bashford, Helmets and Body Armor in Modern Warfare, (New Haven, CT: Yale University Press, 1920). 89. Kaswell, Ernest R., Textile Fibers, Yarns, and Fabrics, (New York, NY: Reinhold, 1953). 100. Metker, LeRoy W., et al. "A Method for Determining Backface Signatures of Soft Body Armors," Tech. Rep. EB-TR-75029 (Aberdeen Proving Ground, MD: U.S. Army Armament Research and Development Command, May 1975); DTIC AD-A012 797. 128. Stoll, Alice M. and Chianta, Maria A., "Heat Transfer Through Fabrics as Related to Thermal Injury," Transactions of the New York Academy of Sciences, vol. 33, no. 7, 1971, pp. 649-670. 162. Vollrath, Fritz, "Spider Webs and Silks," Scientific American, vol. 266, no. 3, March 1992, pp. 70-76. Summary of NIJ Standard 0101.03 -A Performance Standard The .03 standard is a performance standard, not a construction standard. It does not specify the area of coverage, nor does it specify any material to be used in the armor. This permits and encourages technical innovation, including the development of materials and designs providing better ballistic resistance, greater comfort, or lower cost. However, some aspects of the standard were introduced specifically to provide stringent tests of likely weak points of Kevlar fabric armor, which at the time was almost the only type of concealable body armor marketed in the United States. -Certification of Compliance NIJ Standard 0101.03 provides for the *manufacturer* to certify, on the label, that armor is of a *model* that has a type of ballistic resistance defined by the standard if *samples* of the same model have passed the test specified by the standard for that type of ballistic resistance, regardless of who conducts it. Such a test could be conducted by the manufacturer or by an independent ballistic laboratory under contract to t he manufacturer. A manufacturer could truthfully certify a model of armor to comply with NIJ Standard 0101.03 even if it failed the test repeatedly before finally passing it. Partly because of this, a manufacturer's certification, by itself, *may* provide little assurance of design quality. However, manufacturers (or any other interested party) may submit samples of a model of armor to NIJ for NIJ-supervised testing by an NIJ-approved independent laboratory and, if it passes, for certification of compliance by NIJ. NIJ's criteria for certifying compliance, which include the standard itself and a host of other memoranda, prohibit accepting armor of a model that has previously failed an .03 certification test.(7) TAPIC, to which samples must be submitted for NIJ-authorized testing and (if successful) certification, inspects samples and attempts to determine whether the samples are substantially the same as samples previously submitted under a previous model name. Armor certified by NIJ is listed on NIJ's Consumer Product List, which is maintained by TAPIC. Consulting NIJ's Consumer Product List is the only sure way to determine whether NIJ has certified compliance with NIJ Standard 0101.03; this cannot always be determined from the label. Some marketed armor is certified only by the manufacturer and not by NIJ. -Models and Styles of Armor NIJ notes that "For the purposes of the ... body armor certification procedures, the following definitions have been adopted: A body armor MODEL is a manufacturer designation that identifies a unique ballistic panel construction; i.e., a specific number of layers of one or more types of ballistic fabric and or ballistic-resistant material assembled in a specific manner. A body armor STYLE is a manufacturer designation (number, name, or other descriptive caption) used to distinguish between different configurations of a body armor product line each of which includes the same model of ballistic panel. The distinctions between body armor model and style were established to eliminate the necessity of retesting a given body armor model for compliance with the NIJ Standard each time a manufacturer incorporates the model into [a] different style of armor. [145] NIJ certifies the ballistic resistance of a model on the basis of ballistic testing of samples of the model in accordance with the standard; NIJ certifies the ballistic resistance of a style on the basis of inspection of a sample by TAPIC to determine that it does indeed contain a model of ballistic panel already certified to have the ballistic resistance claimed for the style. Thus, all styles of the same model are assumed to have the same ballistic resistance. TAPIC considers garments differing only in color to be of the same style. Differences in the size or cut (i.e., shape) of garments would bake them different styles, not different models, even though size and cut possibly affect ballistic resistance. Differences in stitching of ballistic panels (e.g., box stitch versus quilt stitch) would make the panels different models. -Types of Ballistic Resistance The .03 standard defines six standard types of ballistic resistance for which armor may be tested and provides for custom testing for "special type" ballistic resistance. Each type is defined in terms of the type or types of bullets fired at panels of the armor to test its ballistic resistance (see table 1). Two types of handgun bullets are fired to test for Type I, II-A, II, or III-A ballistic resistance, which soft armor can provide. One type of rifle bullet is fired to test for Type III or IV ballistic resistance, which hard armor can provide.(8) Each standard type of armor is expected to offer protection against the threat associated with it as well as against the threats associated with all other standard types of armor appearing above it in table 1. For this reason, the types of armor defined by NIJ Std.-0101.03 are often referred to as "levels," level II-A being presumably superior to level I, for example. However, a certification test for type II-A ballistic resistance would not actually test resistance to type I threats. In addition, an NIJ guide specifies other threats against which it expects armor of each standard ballistic-resistance level to provide protection (see table 2), even though the .03 test does not actually test resistance to such threats. [145] Table 1 -- Types of Ballistic Resistance Defined by NIJ Standard 0101.03 in Terms of Bullets and Velocities Specified for Testing ------------------------------------------------------------------------ Bullet mass Impact velocity(a) Type Bullet caliber and type (grains) (ft/s) ------------------------------------------------------------------------ I .22 long riflehigh-velocity 40 1,050 .38 round-nose lead 158 850 II-A .357 jacketed soft-point 158 1,250 9-mm full metal jacket 124 1,090 II .357 jacketed soft-point 158 1,395 9-mm full metal jacket 124 1,175 III-A .44 magnum lead semi- 240 1,400 wadcutter gas-checked 9-mm full metal jacket 124 1,400 III 7.62 mm full metal jacket 150 2,750 IV .30-06 armor-piercing 166 2,850 Special custom custom custom ------------------------------------------------------------------------- (a) Minimum velocity; the maximum velocity for a fair hit is 50 ft/s greater. SOURCE: National Institute of Justice, 1987 [144]. Table 2 -- Types of Ballistic Resistance Defined by NIJ Standard 0101.03 in Terms of Guns and Ammunition Against Which Protection is Expected ------------------------------------------------------------------------- Type Threat ------------------------------------------------------------------------- I .22, .25, and .32 caliber handguns, .38 Special lead round-nose II-A .38 Special high-velocity, .45s, low-velocity .357 Magnum & 9-mm, .22 rifles II Higher velocity .357 Magnum and 9-mm III-A .44 Magnum and submachine gun 9-mm III High-power rifle: 5.56mm, 7.62 mm FMJ, .30 carbine, .30-06 pointed soft point, 12-gauge rifled slug IV Armor-piercing rifle bullet, .30 caliber (1 shot only). ------------------------------------------------------------------------- SOURCE: National Institute of Justice, 1987 [144] and 1989 [145]. -Selection of Samples The NIJ standard specifies that "Four complete armors, selected at random and sized to fit a 117 cm (46 in) to 122 cm (48 in) chest circumference, shall constitute a test sample. (Note: The larger the size, the more likelihood that all ballistic testing will fit on just two complete armors.)" In quality assurance, "selected at random" usually means "selected at random with uniform probability" -- i.e., sampling should ensure that all units of the model should have the same chance of being selected to be tested. However, this is impossible if samples are selected for certification testing before production of the model has been discontinued. Typically samples are selected after only a few units have been produced; consequently, the sampling procedure does not guarantee that the samples are representative of yet-to-be-produced units of the model, particularly of smaller sizes. -Conduct of the Test Armor to be tested is mounted on a flat block of inelastic backing material -- typically modeling clay -- to be shot. The impact velocity of each bullet is measured using a ballistic chronograph (see figure 2). If the bullet hits an appropriate point on the panel at an impact velocity within specified limits (see table 1), the impact is considered a fair hit. The test requires a fair hit in each of six specified areas on each panel in a specified sequence (see figure 3). Each shot must impact at least 3 inches from the edge of the panel and at least 2 inches from the closest point of impact of any prior shot. Figure 3 -- Sequence of Aim Points on Each Panel, as Specified in NIJ Standard 0101.03 * #1 #4 * * #6 * #5 #2* * #3 All shots at least 7.6 cm (3 in) from any edge and at least 5 cm (2 in) from another shot SOURCE: National Institute of Justice, 1987. In tests of Type I, II-A, II, or III-A ballistic resistance, four complete armors, typically including eight armor panels (four each front and back) are usually shot. Each ballistic element (front or back panel) is sprayed with water and then shot with test bullets of the first type, then another one is sprayed and shot with test bullets of the second type. This is repeated with unsprayed, dry samples. This requires a minimum of 48 shots per test: 2 element types (front and back) x 6 shots each x 2 types of bullets x 2 wetness conditions. If the velocity of a shot is too low and it does not penetrate the panel, or if the velocity of a shot is too high and it does penetrate the panel, the shot is repeated, aimed at least 2 inches from the closest point of impact of any prior shot. However, in more than eight shots (of one caliber) may be fired at any panel.(9) The armor cannot be certified if any fair shot penetrates. After the first fair shot at each panel, the panel is removed from the backing and the depth of the crater (called the backface signature or BFS) is measured. If the BFS exceeds 44 mm or if the armor was penetrated, it fails; if not, the panel is replaced on the backing without filling the crater or otherwise reconditioning the backing material, and testing for penetration is resumed.(10) The standard prohibits adjusting the panel (e.g., patting it down) thereafter, unless it is reused for testing with a second type of bullet. NIJ Standard 0101.03 specifies that armor be tested on a block of backing material at least 4 inches thick "and of sufficient length and wdith ... to completely back the armor part to be tested." The standard does not specify unambiguously that the backing must be flat, and in fact requires it to be built up to achieve contact with the armor when testing female armor with bust cups or when testing rigid armor for Type III or IV ballistic resistance. However, in practice, a flat surface is used in other cases. Until recently, the testing of a whole armor garment with removable ballistic panels (the usual configuration) was precluded by the requirement that each ballistic element (e.g., panel) be tested separately. (Although the standard explicitly allows testing a whole armor garment if it is made in one part without removable ballistic panels, this may be precluded by the provision that requires the backing to be "of sufficient length and width ... to completely back the armor part to be tested.") In a letter dated April 27, 1992, NIJ directed H.P. White Laboratory, Inc., that effective June 1, 1992, it should test samples for compliance with NIJ Standard 0101.03 by mounting the whole armor garment on a smaller clay block in a curvilinear frame (see photo) -- a highly abstract mannequin.(11) The standard itself was not changed. This summary does not cover all details of the standard; the interested reader is referred to the standard itself and to appendix A of this report for additional details. -Validity of the Test The standard does not explain the rationale for its provisions but does refer readers to and NIJ guide that discusses the origin of the standard briefly and cites detailed reports of research considered by the drafters of the standard. The standard specifies how to conduct a ballistic test of samples of a model of armor under controlled conditions, in order to measure properties of the samples (types of "ballistic resistance") that can reasonably be expected to be related to the protection that other samples of the same model will afford wearers in service. However, the details of the relationship are uncertain and disputed; no body of data reliably links performance in the lab with performance in service. This situation is common in consumer-product safety testing, but it leaves room for legitimate questioning of the meaning of passing the test. FOOTNOTES 7. We distinguish between NIJ's *certification criteria*, which require one test according to NIJ Standard 0101.03 and have other requirements as well, and the ballistic *test* specified by the standard, which may be performed for NIJ certification or for other purposes, such as manufacturer's certification of compliance or testing samples of certified models for quality assurance (commonly called "retesting"). 8. The test procedure for "special type" ballistic resistance is the same as for standard types of ballistic resistance, except the person ordering the testing (e.g., a manufacturer) specifies the type and nominal velocity of the test projectile to be used. For example, a manufacturer could have armor tested for NIJ certification of Special Type ballistic resistance to a .45-caliber bullet, a 12-gauge rifled slug, or buckshot at a specified velocity. Special-type armor is not necessarily expected to protect against the threat associated with any other type. 9. To provide for contingencies, six complete armors (12 panels) must be submitted for a Type I, II-A, II, or III-A test. 10. NIJ Standard 0101.03 specifies that testing shall be continued after each BFS measurement if it is no greater than 44 mm, and after shooting six fair shots per panel if none penetrated. It neither requires nor prohibits continuation of the testing in other cases -- i.e., after failures However, NIJ has directed H.P. White Laboratory, Inc. (HPWLI), the only laboratory authorized to conduct testing for NIJ certification, to complete the testing despite disqualification of the armor. 11. "Retesting" (testing samples of a model certified to comply with NIJ Standard 0101.03) is to be done using the type of test fixture used in the certification test. REFERENCES 144. U.S. Department of Justice, National Institute of Justice, Technology Assessment Program, Ballistic Resistance of Police Body Armor, NIJ Standard 0101.03 (Washington, DC: National Institute of Justice, April 1987). 145. U.S. Department of Justice, National Institute of Justice, Technology Assessment Program, Selection and Application Guide to Police Body Armor, NIJ Guide 100-87 (Washington, DC: National Institute of Justice, February 1989). OPTIONS FOR THE DEPARTMENT OF JUSTICE (I have summarized this section) (Italics in the original document are indicated by enclosing the text in asterisks) OPTIONS FOR THE DEPARTMENT OF JUSTICE It is clear the standard should be revised -- eventually. It could be revised now to reduce the latitude in test procedures permitted by the standard. This would limit lab-to-lab and test-to-test variations in test conditions, which might be partly responsible for variations in test results. The section Revise NIJ Standard 0101.03 (below) describes several such revisions; they include specifications of bullets and backing material, reducing the range of allowed backing-material temperature, measuring backing-material temperature and consistency more frequently, and patting down armor between test shots. Revising the standard to specify a number of specific laboratory proceduresalready used at H.P. White Laboratory, Inc., would further limit possible lab-to-lab variations in test conditions. (Recall that any individual with two guns, modelling clay, a thermometer, a steel ball, and a ballistic chronograph can test samples of armor and certify the model's compliance with the NIJ standard on the labels of other units of the model.) Moreover, as discussed above in Findings, the validity of the current test has not been demonstrated -- nor can it be until acceptable risks are specified. This lack of demonstrated vaility does not require revising the current standard. Specifying acceptable risks would allow the validity of the current test to be decided scientifically and would givbe NIJ a yardstick for assessing options for revising its test and its certification process. NIJ should specify the types and degrees of injuries and incapacitation by penetrating and nonpenetrating bullets that the armor is to prevent and the maximum acceptable risks of such injuries and incapacitation (as well as the statistical confidenc with which acceptable risk must be demonstrated). A statement of goals could be of the following generic form: Certified armor should: (1) Stop each shot, up to n per panel, with probability Ps or greater. (2) Leave wearer ambulatory with no injury rated higher than i on the Abbreviated Injury Scale (49)[88] after each stopped shot, with probability Pa or greater. Reenactments or other tests should: (3) Demonstrate that armor meeting the certification criteria will accomplish goal (1) with at least C1-percent confidence and goal (2) with at least C2-percent confidence. Revise NIJ Standard 0101.03 Whatever changes are made, some of the latitude in test procedures permitted by the standard should be reduced to limit lab-to-lab and test-to-test variations in test conditions, which might be partly responsible for variations in test results. Since NIJ Standard 0101.03 was issued in 1987, the H.P. White Laboratory, Inc. (HPWLI), which currently is the only ballistic test laboratory authorized by NIJ to do testing for certification *by NIJ* of compliance with the standard, has adopted particular ways of conducting the test in the interest of reproducibility. NIJ has also issued directives instructing H.P. White Laboratory to perform parts of the test in particular ways that are not the only ways allowed by the standard. Other laboratories attempting to cinduct a test in accordance with the standard -- e.g., for developmental testing of a new model -- might conduct their testing in accordance with the standard but not exactly in accordance with the procedures H.P. White Laboratory would use for certification testing of the model. -Revise the Backface Signature Limit *The backface signature limit specified by the standard could be revised based on the maximum risk of injury NIJ will accept and the statistical confidence it requires in the validity of the BFS test.* The impact of a bullet stopped by armor can kill or injure the wearer. Bruising and minor laceration is to be expected, but some test of the ability of armor to protect its wearer from critical injury is needed. The NIJ test, which is based on the depth of the crater made in clay behind the armor wien it is hit, serves this purpose. Of the armors that have stopped bullets in assaults, those that would have passed the NIJ test (for protection from a stopped bullet of the type it stopped in an assault impacting at the same speed as in the assault) limited the chance of death or life-threatening injury to about 1 in 300, which is much smaller than the maximum risk acceptable to NILECJ in 1976: 1 in 10. Armor fails the NIJ test if the depth of the crater (called the backface signature, or BFS) made in the clay behind the armor exceeds 44 mm. The 44 mm limit was based in part on NILECJ-sponsored experiments in which animals wearing one type of armor were shot with one type of bullet at a specified nominal velocity. (25, 26) No wearer of NIJ-certified armor has suffered a type of injury that this test was designed to prevent, even though it was not intended to prevent such injuries with certainty. OTA's analysis shed little light on the discrimination of the test -- i.e., whether the risk to wearers of armor that would have failed the test was substantially greater than the risk to wearers of armor that would have passed the test. Although NIJ's 44-mm BFS limit has been a topic of considerable controversy, it has not been a major cause of certification-test failures: as of October 31, 1991, less than 3 percent of the models of armor submitted for an NIJ certification test failed soley because of excessive backface signature.(27) -Require Patting Down of Armor Between Shots *The standard could be revised to require patting down of armor between shots.* This would simulate typical assaults (those that cause only one impact per panel) more realistially than does the current test. However, it might simulate assaults causing multiple impacts per panel less realistically. It would limit inadvertent shot-to-shot and test-to-test variability of test conditions, and would limit opportunities for any operator (tester) to deliberately influence the probability of passing by aiming either at or between the "hills" caused by the bunching effects of previous shots. It would decrease the stringency of the test in that it would give armor of models susceptible to ply separation in testing an increased probability of passing. -Specify Standard Bullets *The bullets to be used in the test could be specified more precisely.* The probability with which a commercially available bullet of specified mass and caliber will penetrate armor at a specified velocity depends on the bullet's construction and composition. [28] A bullet that deforms may be stopped by relatively few layers of armor; many more layers may be needed to stop sharp fragments of a hard or steel-jacketed bullet. Specifying more precisely the bullets to be used in the test could increase reproducibility of test results. It would not simulate the diversity of the threat faced by police officers (neither does the current set of test bullets), but reenactments could assess the reliability with which armor tested with standard bullets stops bullets that hit wearers. -Specify Standard Backing Material *The backing material to be used could be specified.* In practice, only one backing material, Roma Plastilina No. 1 modeling clay, is used by HPWLI for NIJ certification tests. However, NIJ Standard 0101.03 does not require it; a tester may use any material that passes the "drop test" specified to check the consistency of the backing material. Some backing materials conditioned to pass the drop test yield different backface signatures at the much higher deformation velocities typical of a ballistic test conducted in accordance with NIJ Standard 0101.03.(51) Thus the drop test does not assure that backface signatures produced in different backing materials behind similar armors by similar bullets impacting at similar velocities will be the same. -Reduce Tolerances on Backing Material Properties *The allowable range of backing material temperature could be reduced, and the temperature or consistency of the backing material (or both) could be required to be measured at specified time intervals or stages of ballistic testing.* The consistency (flowability) of clays commonly used for backing has been shouwn to be very sensitive to clay temperature. Variation in the temperature of clay backing material could make the difference between passing and failing NIJ's test for protection from stopped bullets. In 1977, the Aerospace Corporation recommended that, for adequate reproducibility, backing material be maintained at 70 degrees plus or minus 2 F. NIJ Standard 0101.03 allows backing material to have a temperature between 15 and 30 C (59 and 86 F) during testing. It requires the consistency of the material to be tested three times by dropping a specified weight from a specified height and measuring the depth of the crater it makes. In practice, (at the H.P. White Laboratory), all three drop tests are conducted before -- not during or after -- testing. Possibly the consistency may chance during testing, e.g., as a result of bullet impacts or as the material's temperature approaches ambient temperature (which is required to be in a narrower range than the material's temperature). In tests observed by OTA, the backing material cooled during testing.(53) Possibly this happens in a uniform way at H.P. White, but it could vary from lab to lab. Moreover, the latitude permitted by the standard could be exploited to influence test results. -Certify Wet and Dry Ballistic Resistance Separately *The wet test could be mandatory or optional.* Some purchasers or wearers may prefer armor with inadequate wet ballistic resistance because of cost or comfort. They may suspect the risk of its becoming dangerously wet is so low they would accept it. But to learn what the risk is, they would have to weigh their armor regularly to measure and record water retention and analyze the records to calculate frequency with which retention exceeds dangerous levels. In compensation, wear rate might be increased among those who find armor with inadequate wet ballistic resistance more affordable or comfortable but who also value NIJ's certification. Subjecting armor only to the dry testing specified in the NIJ standard would reduce the stringency of the test, even for armor that performs as well wet as dry. If NIJ wished to compensate for this and maintain the stringency of the test, it could offer a choice of the current wet-dry test or a double-dry test with the same number of fair shots required. -Rate the Ballistic Resistance of Each Certified Model With a Score *The standard could specify a way to rate the ballistic resistance of each certified model with a score*, such as the V50 ballistic limit -- the velocity at which test bullets have a 50 percent chance of penetrating. The present certification test is a pass/fail test, although armor may be tested for resistance to any type of bullet at any velocity. Nevertheless, knowing only that model has passed does not indicate the velocity at which the test bullets would be expected to penetrate it. -Use Anthropomorphic Test Fixture *The standard could be revised to allow or require testing of a whole armor garment on an anthropomorphic test fixture to which the armor could be affixed by the strapping or fasteners a wearer would use.* This would improve the realism of the test and would be necessary to test integral armor -- armor made from a single panel of ballistic material stitched so that it can not be spread flat on a clay block. Assure Quality -Certify Lots *NIJ could certify lots, rather than models, of armor.* To exercise this option, NIJ would have to 1. Define a lot. 2. Specify a sampling plan -- i.e., the number of samples from each lot to be tested, and criteria for acceptance and rejection based on test results. 3. Ensure the samples to be tested are seleted randomly from each lot. -Establish a Voluntary Quality-Control Program *NIJ could establish and supervise a voluntary quality control program analogous to the Listing or Classification programs of Underwriters Laboratories, Inc. (UL). UL Classification of a model of armor would be based partly on ballistic testing of samples and partly on inspection of the manufacturer's manufacturing and quality assurance processes by NIJ or a contractor. FOOTNOTES 25. The research indicated 44 mm was an appropriate, if not conservative, BFS limit for .38-Special lead round-nose bullets impacting at about 800 feet per second (a type I threat) on7-ply Kevlar armor. NILECJ Standard 0101.01 extrapolated the limit to all armors at all ballistic-resistance levels, assuming the BFS limit that would limit the risk from a high-energy bullet stopped by any armor to 10 percent would be no greater, and might be smaller, than the BFS limit for .38-Special bullets on 7-ply Kevlar armor [Lester Shubin, pers. comm., 13 Nov. 1991]. This was a reasonable conjecture at the time. 26. The NILECJ also funded Army experiments in which armored goats were shot with .357 magnum and 9-mm bullets, as was armor on clay backing, but research was not completed or published. 27. This figure is for samples submitted to TAPIC and tested for certification of model compliance with NIJ Standard 0101.03. 49. We expect NIJ would want armor to prevent injuries with AIs ratings of 6 (fatal), 5 (critical: survival uncertain), and 4 (severe, life-threatening: survival probable) with a high probability. NIJ could allow injuries rated 3 (severe, not life-threatening) or below on the AIS, on the grounds that requiring armor to prvent them may have a negative, but as yet unquantified, effect on wear rate. 51. For example, in tests conducted by the British Police Scientific Development Branch, under otherwise similar conditions the average (viz., fitted) backface signatures produced in U.S.-made Plastilina and U.K.-made Plasticine were similar at impact velocities of 350 m/s but differed by about 4.4 mm for each 100 m/s above or below 350 m/s. [29] Cf. [28, 84] 53. However, after the last shot at each panel, craters were filled with clay warmer than the rest of the face of the clay block. REFERENCES 28. Brown, Eric, "Home Office Ballistic Standard," pp. 127-142 in L. Tobin (ed.), op. cit. infra. 29. Brown, Eric, (Head, Firearms and Armour Programme, U.K. Home Office Police Scientific Development Branch), personal communication, 29 Nov. 1991. 84. Iremonger, M.J. and Bell, S.J., "Simulation of Behind-Armour Trauma," pp. 191-204 in L. Tobin (ed.) op. cit. infra. 88. Joint Committe of the American Medical Assoc., American Assoc. for Automotive Medicine, and the Society of Automotive Engineers, "The Abbreviated Injury Scale (AIS) -- 1976 Revision," (Morton Grove, I: American Assoc. for Automotive Medicine, 1976).