Handguns predominated as the firearm of choice in shooting-related crimes, especially in the United States of America. As with most firearms, the fired ammunition components may acquire sufficient unique and reproducible microscopic marks to be identifiable as having been fired by a single firearm. Making these comparisons is correctly referred to as firearms identification, or sometimes called as "ballistics". Historically, and currently, this forensic discipline ultimately requires a microscopic side-by-side comparison of fired bullets or cartridge cases, one pair at a time, by a forensic examiner to confirm or possibly eliminate the two items as having been fired by a single firearm. For this purpose, the traditional tool of the firearms examiner has been what is often called the ballistics comparison microscope. Comparison microscope is essential for the forensic ballistics expert in comparing bullets and spent cartridge casings. The interior of a gun's barrel is machined to have grooves that force the bullet to rotate as it travels along it. These grooves and their counterpart, called "lands" imprint groove and land impressions on the surface of the bullet. Together with these land and groove impressions, imperfections on the barrel surface are incidentally transferred to the bullet's surface. Because these imperfections are randomly generated, during manufacture or due to use, they are unique to each barrel. These patterns or imperfections, therefore, amount to a "signature" that each barrel imprints on each of the bullets fired through it. It is this "signature" on the bullets imparted due to the unique imperfections on the barrel that enable the validation and identification of bullets as having originated from a particular gun. Comparison microscope is used to analyze the matching of the microscopic impressions found on the surface of bullets and casings.
When a firearm or a bullet or cartridge case are recovered from a crime scene, forensic examiners compare the ballistic fingerprint of the recovered bullet or cartridge case with the ballistic fingerprint of a second bullet or cartridge case test-fired from the recovered firearm. If the ballistic fingerprint on the test-fired bullet or cartridge case matches the ballistic fingerprint on the recovered bullet or cartridge case, investigators know that the recovered bullet or cartridge case was also fired from the recovered gun. A confirmed link between a specific firearm and a bullet or cartridge case recovered from a crime scene constitutes a valuable lead, because investigators may be able to connect the firearm to a person, who may then become either a suspect or a source of information helpful to the investigation.
Since, ballistic identification has benefited from a long series of structural, scientific and technological advances, law enforcement agencies have established forensic labs and researchers have learned much more about how to match bullets and cartridge cases to the guns used to fire them, and comparison microscopes have become more sophisticated. By the end of the 1980s, ballistic identification was an established subspecialty of forensic science. Modern comparison microscope combines the latest opto-mechanical developments in light microscopy with ease of use and ergonomics, which allows the forensic examiner to achieving results with highest accuracy and efficiency. The comparison microscope like Leica FS4000 allows highly precise comparison of two objects at magnification up to 1500x and gives reliable proof of slightest differences in the microstructure, texture and colour. It allows side by side comparisons of two slides as well as the ability to view each slide individually.
Intelligent Automation Inc., an American Research and Development firm, has developed and implemented a visualization tool called the "Virtual Comparison Microscope" that allows the firearms examiner to verify the degree of similarity between any two tool-marks in question. The Virtual Comparison Microscope was designed to simulate the operation of the comparison microscope commonly used by firearms examiners. It is capable of rendering a 2D view of the 3D surfaces in a manner similar to that of the comparison microscope. It also enables the examiner to translate one tool mark or striae with respect to the other, overlap them, modify illumination conditions, zoom in and out, adjust the point of view of the user, and even provides the ability to create a split image on the screen that includes a hair-line to demarcate one tool-mark on the left of the screen from the other on the right.
The Virtual Comparison Microscope allows for all the viewing conditions to be same for both tool-marks, and it does not require the adjustment of either the independent illumination or the focus of the tool-marks. Other unique characteristics of the Virtual Comparison Microscope include its ability to simulate any material or "palette" which may be useful to the user as well as adjustment of the angle of incidence of the light and the light intensity that can assist in emphasizing certain features in the 3-D images for better visualization. Some of the capabilities of the Virtual Comparison Microscope have no counterpart in a conventional comparison microscope. The Integrated Ballistics Identification System (IBIS) system, developed by Forensic Technology, of Montreal, is a modern configuration of BulletTRAX-3D paired with MatchPoint Plus. This integrated system allows for image data entry, storage in a server and correlations (comparison of surface topography) between new and stored bullet image data. Search results are ranked and images are made available to examiners for preliminary evaluations prior to actual microscopic examinations. The Latest Configuration of IBIS BulletTRAX-3D combined with MatchPoint Plus is now being offered by Forensic Technology Inc., as an advanced technical solution for case linkage using fired bullets recovered at shooting scenes and from shooting victims. This integrated workstation is designed as a tool for the firearms examiner in preparing for the ultimate procedure, the physical microscopic intercomparison of fired bullets. The system as a whole takes advantage of the strength of computer technology by making massive numbers of eliminations of bullets from previously entered cases as candidates for physical comparison and potential case linkage with a bullet from a current case. It then combines that information with the ability of the human examiner to make the final decisions regarding those relatively few candidates selected by the system for the examiner's consideration and possible microscopic comparison. IBIS ,Integrated Ballistics Identification System, is currently used by forensic examiners over 30 countries and territories.
BulletTRAX-3D revolutionized the way bullet evidence is analyzed, and many forensic experts believe that this technology will eventually replace the comparison microscope. Integrated Brass TRAX-3D, a device designed to allow investigators to capture and examine both three-dimensional and two dimensional images f cartridge cases. The BrassTRAX-3D and the BulletTRAX-3D bullet imaging device to form the IBIS-TRAX 3D line of ballistics identification systems. The IBIS - TRAX 3D line is designed to suggest possible matches between pairs of spent bullets and cartridge cases. The system is also engineered to include three-dimensional image viewing tools, modular flexibility, and higher automation.
In the 1990s, computers joined comparison microscopes as essential tools of forensic examination. With advances in digital imaging technology and data storage capacity, forensic examiners envisioned a centralized database of images of bullets and cartridge cases that could be compared against a bullet or cartridge case recovered from a crime scene. By the mid 1990s, two such systems emerged. The first system, developed by the Federal Bureau of Investigation (FBI), was called "Drugfire." Drugfire used imaging software to capture, catalog and compare digital images of cartridge cases, bullets were added later. A forensic examiner would capture an image of a recovered bullet or cartridge and compare it with similar images from the database. Drugfire enabled the examiner to see many images of potential matches on one screen, greatly speeding up the process. However, Drugfire did not rank the images by how close a match they were, leaving that determination entirely to the examiner. More than 170 law enforcement agencies nationwide participated in the Drugfire program. The second system, developed by the Bureau of Alcohol, Tobacco and Firearms (ATF), was originally called "Ceasefire." Like Drugfire, Ceasefire used imaging software to capture images of the markings on bullets and included a sophisticated comparison algorithm that automatically identified likely matches. Rather than requiring the examiner to sift through dozens or hundreds of images, the computer presented the examiner with a ranked list of the most likely matches. When the ATF expanded Ceasefire to include cartridge cases, it renamed the program the Integrated Ballistics Identification System (IBIS).
In 1997, the ATF and the FBI agreed to try to combine Drugfire and IBIS to reduce the cost and inefficiency of maintaining both systems. However, technical obstacles prevented integrating the systems, sparking a pitched battle for supremacy. supporters of the FBI's Drugfire system preferred its imaging technology and the degree of control they retained, while supporters of ATF's IBIS system praised its automation and speed. After several years of wrangling, a compromise emerged. The new system would adopt IBIS's imaging technology and comparison algorithms while relying on the FBI's telecommunications network. Although a few devotees continued to use Drugfire on their own, IBIS became the standard centralized system. The National Integrated Ballistic Information Network (NIBIN) was born.