This image shows how a microstamped primer on a cartridge casing is visualized using the Olympus LEXT platform. The image highlights the benefits of analysis and visualization using Confocal microscopy. Seen here are increases in resolution, depth of focus and contrast that are far better then conventional optical methods. |
(Olympus Industrial America: Orangeburg, New York) -- Microstamping is an evolutionary step in the field of firearm and tool mark identification. It places small microembossing structures onto the interior surfaces of semiautomatic handguns, which come in contact with the bullet cartridge casing as it cycles through the firearm before it is ejected. Evidence found at the crime scene bearing microstamps can reveal explicit information about the gun used in the commission of a crime. The technology, coinvented by Todd Lizotte and Orest Ohar, was designed to aid the traditional forensic community and the new computer statistics mapping (COMPSTAT) crime analysis units that are being integrated around the nation.
Microstamping microembosses structures that take the form of alphanumeric or encoded barcodes that allow forensic investigators the ability to identify the firearm’s make, model, date of manufacture, and serial number. This is critical technology, as an average of 38 percent of crimes committed with firearms remain unsolved nationwide. The primary evidence left at the crime scene is expended cartridge casings. Yet without recovering the gun, these cannot be used to trace the origin of the gun nor its “time to crime.” Microstamped information recovered from the cartridges, however, provides an immediate link to the gun, even if it isn’t recovered. Law enforcement will be able to trace such links to other crimes, developing patterns of movements, and clusters of crime activity using COMPSTAT techniques. Such methods allow police to narrow in on criminals using illegal firearms and their suppliers who traffic in stolen weapons.
However, microstamping is only as reliable as the firearm and the subsequent imaging technology applied to extract the information. Some researchers investigating the ability of microstamping to transfer codes found that due to the variability of the firearm’s mechanical dynamics, some microstamps can become illegible due to multiple strikes, oscillations of the gun, or pin dragging. These researchers limited themselves to using low magnification (40× to 60×) optical microscopy without optimized lighting to match the metallurgical surfaces being viewed.
In 1999, Lizotte found that by using scanning electron microscopy (SEM), he was able to resolve the elusive multiple microstamped images embossed in the cartridge brass. The SEM’s increased depth of focus and monochromatic electron-beam scanning delivered images that revealed a rich depth of information about the gun. He also showed that with the use of standard forensic chemical etching and casting techniques, these microstamped codes could be further enhanced. However, SEM imaging is time-consuming and expensive.
Lizotte began looking for a mid-level technology that bridged the gap between optical microscopy and SEM imaging. After evaluating offerings in the metrology industry, the Olympus LEXT Confocal microscopy method was determined to provide that middle ground.
The Olympus LEXT system’s ability to provide image enhancement and 3-D surface visualization opened new doors to the analysis of microstamps and many other forensic imaging needs. It balances visualization between optical imaging and by scanning a monochromatic laser through slices of the objects depth. This increases the depth of focus and the contrast of the brass surface, revealing details unseen in using only the optical image. Lizotte has further demonstrated that even the multiple-hit microstamped cartridges, which are difficult to resolve under optical microscopes, are legibly resolved using the Olympus LEXT Confocal microscope.
Olympus can be found on the web at www.olympusmicroimaging.com.
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