Ballistic Imaging


  National Research Council


Telephone News Conference

March 5, 2008


Opening Statement


John Rolph


Professor of Statistics, Marshall School of Business, University of Southern California


Chair, Committee to Assess the Feasibility, Accuracy, and Technical Capability

of a National Ballistics Database



Good morning, and thanks for joining us for the release of our report Ballistic Imaging.


In recent years, the desire to aid the investigation of gun crimes and lower the nation's level of gun violence has led legislators and advocacy groups to urge new initiatives to help link ballistic evidence found at crime scenes to the weapons from which they were fired.


One solution that has been proposed is the creation of a reference database that would contain ballistic images from all new and imported guns sold in the United States. The National Institute of Justice of the U.S. Department of Justice asked the National Research Council to assess how accurate and useful such a database is likely to be.  Our committee's new report does so, and also discusses a complementary approach called "microstamping," a newer technique to help link cartridge cases and bullets to guns.


Ballistic images depict the marks left on bullets and cartridge cases when they are fired from a gun. Called toolmarks, these marks have been assumed to be unique to each gun and have long been used to investigate crimes. For example, an investigator might compare a bullet found at a crime scene to one test-fired from a suspect's gun, to try to determine whether the toolmarks match.


Databases of ballistic images help investigators conduct these comparisons on a far larger scale, allowing them to search across the images of toolmarks from many thousands of firearms.  An existing national database run by the Bureau of Alcohol, Tobacco, Firearms, and Explosives, for example, contains ballistic images from weapons used in crimes and from guns recovered by police.  It is important to note that database searches only suggest possible matches; a final determination of a match is made by a firearms examiner, through direct physical comparison of the exhibits in question.


A national reference database would include images from all new and imported guns sold in the United States, not just weapons linked to crimes. When a new gun is sold, images of cartridge cases fired from it would be entered into the database. Investigators around the country could enter images of crime-scene ballistic evidence and search the reference database for images of toolmarks that match -- which would presumably help them identify possible weapons and the places they were sold. Such reference databases have already been established in Maryland and New York. 


The committee concludes that a national reference database of ballistic images should not be established. 


Images from more than a million guns would be entered into such a database every year, and many of these would have similar toolmarks. Because current technology for collecting and comparing toolmarks is not sufficiently precise in distinguishing extremely fine marks among so many images, searches would return too many possible matches to be practically useful. In addition, the type or brand of ammunition used in the initial firing of a gun would not necessarily be the same as the ammunition later used in a crime.   This difference could be a significant source of error in generating possible matches. 


The committee was not charged with issuing a verdict on whether toolmarks are unique -- that is, whether each gun leaves marks that could not be made by any other firearm. Nor was the committee charged to recommend whether toolmark evidence should be admissible in court.  However, it became clear to the committee early on that the assumption that toolmarks are unique to each gun has not yet been fully scientifically demonstrated. Much more research would be needed to determine whether toolmarks are truly unique, or even to estimate the probability that they are unique.


Consequently, the committee advises against one statement frequently made by firearms examiners -- that toolmarks link bullets or casings to a particular gun "to the exclusion of all other firearms."  Given that uniqueness has not been demonstrated, such statements do not have a firm statistical basis. These claims, which imply an error rate of zero, also don't reflect the element of subjectivity involved in declaring a match, a determination that's always made by a firearms examiner.


The conclusion that uniqueness has not been fully established doesn't mean that toolmarks or ballistic imaging technologies are not useful.  It is clear to the committee that the toolmarks generated by firing guns are not completely random and volatile, and that the current imaging technology is definitely helpful in generating leads for law enforcement investigation.  Thus, our report recommends many ways to improve ATF's existing database of crime-related ballistic evidence, called the National Integrated Ballistic Information Network or NIBIN, which permits investigators at about 230 participating law enforcement agencies to search evidence against images from their own jurisdiction as well as from other departments.


For example, ATF should consider establishing protocols for entering images of multiple exhibits from the same gun, ideally involving various types of ammunition; currently, only a single exhibit is entered in some jurisdictions. The report also recommends several ways to improve the database's technical platform -- for example, by making it simpler to conduct searches across multiple regions of the country.  In addition, we recommend more research on a possible future shift from using two-dimensional photographic techniques to using three-dimensional surface measurement techniques.


We also urge further research on microstamping, a promising alternative to creating a national ballistic database that has been legislated in California and is pending in Congress. This technique places a unique identifier -- such as an alphanumeric code -- on gun parts or ammunition, and it would have the formidable advantage of imposing uniqueness on ballistic evidence.  However, studies have not yet determined how durable microstamped marks are under various firing conditions, how susceptible they are to tampering, or what their cost would be for manufacturers and consumers. We strongly encourage research on these and other issues related to microstamping, as this method may indeed be a viable future approach to firearms investigation.  


This concludes my opening statement. We are now happy to take your questions.