A dissecting microscope, sometimes known also as stereo microscope or comparison microscope, is a device used to analyze side-by-side specimens. It consists of two microscopes connected to an optical bridge, which results in a split view window. The dissecting microscope is used in forensic sciences to compare microscopic patterns and identify or deny their common origin. The idea behind the dissecting microscope is simple. Two microscopes are placed next to each other and the optical paths of each microscope are connected together by the optical bridge would help the forensic examiners to simultaneously compare two specimens instead of depending on their memory. The dissecting microscope had major roles in early forensics. Its history dates back to the 1920s where it was used in forensic ballistics. The accused murderers and anarchists Nicola Sacco and Bartolomeo Vanzetti was one such case. Dissecting microscope was used for ballistic identification evidence in 1921 to help secure convictions of accused murderers Sacco and Vanzetti.

Philip O. Gravelle, a chemist, developed the dissecting microscope for use in the identification of fired bullets and cartridge cases with the support and guidance of forensic ballistics pioneer Calvin Goddard. It was a giant leap in the science of firearms identification in forensic science. The firearm from which a bullet or cartridge case has been fired is identified by the comparison of the unique stripe left on the bullet or cartridge case from the worn, machined metal of the barrel, breach block, extractor, or firing pin in the gun. It was Gravelle who mistrusted his memory. “As long as he could inspect only one bullet at a time with his microscope, and had to keep the picture of it in his memory until he placed the comparison bullet under the microscope, scientific precision could not be attained. He invented the dissecting microscope and Goddard made it work.” Calvin Goddard perfected the dissecting microscope for use in bullet and cartridge case comparison and popularized it. Sir Sydney Smith also appreciated the idea, emphasizing the importance of stereo-microscope in forensic science and firearms identification. He took the dissecting microscope to Scotland and introduced it to the European scientists for firearms identification and other forensic uses.

In 1929, using a dissecting microscope, Calvin Goddard and his partner Phillip Gravelle used similar techniques they used in the Sacco-Vanzeti case to free the Chicago Police Department any participation in the St. Valentine’s Day Massacre. During the 1960s there were proposals to somehow “computerize” the process of microscopic comparisons of fired ammunition components, but at that time neither the software nor the hardware existed to implement the theories. By the 1980s that situation had changed radically, as represented by high-capacity computer systems adapted to the requirements of digital imaging, pattern recognition, image storage and comparison algorithms. Cooperation between private industry, law enforcement and forensic subject matter experts lead to the evolution of the Integrated Ballistics Identification System. It is deployed worldwide by Forensic Technology, Incorporated of Montreal.