Microstamping Analysis Enhanced By Confocal Microscopy

Microstamping is an evolutionary step in the field of “Firearm and Tool Mark Identification.” It places small micro-embossing structures onto the interior surfaces of semi-automatic 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 the crime. The technology, co-invented by Todd Lizotte and Orest Ohar, was designed to aid both the traditional forensic community and the new COMPSTAT (computer statistics mapping) crime analysis units being newly integrated around the nation.

Although, 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. However these researchers limited themselves to the use of low magnification (40X to 60X) optical microscopy without optimized lighting to match the metallurgical surfaces being viewed.

In 1999, Mr. 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 proved to deliver images that revealed a rich depth of information about the gun. He also showed that with the use of standard forensic chemical etching techniques and casting techniques, these Microstamped codes could be further enhanced. However, SEM imaging is time consuming and expensive.

Mr. 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 3D surface visualization opened new doors to the analysis of both Microstamps and many other forensic imaging needs. It balances visualization between both optical imaging and by scanning a monochromatic laser through slices of the objects depth. This increases both the depth of focus as well as the contrast of the brass surface, revealing details unseen in just the optical image alone. Mr. 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.

Figure One 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. Figure Two shows how a Microstamped breech face mark on a cartridge can be more easily observed with Confocal techniques.

Both figures clearly show that the Olympus LEXT Confocal Microscope system is a cost effective way for forensic laboratories to visualize and analyze “Firearms and Tool Marks” on all manner of objects, not just cartridge casings. All of this is achieved without having to commit to costly and time consuming Scanning Electron Microscope techniques.