The Stereo Microscope in Forensic Applications

The 3D visualization is created by combining the microscope's technology with inherent functions of the human brain. Specifically, two optical paths deliver variations of the same image to each of the eyes by altering the viewing angle slightly. The slight difference in viewing angle between both eyes results in subtle illumination and shading variations.  The brain receives this input and interprets it as a single 3D image.

Stereo microscopes offer both binocular (uses two eyes) and stereoscopic (3D) visualization, which means there are two eyepieces requiring both eyes and the resulting image as perceived by the brain is in 3 dimensions. This technology increases depth perception, which supports the examination of a sample's topography. Viewing the same sample through a single lens might cause an investigator to miss a critical pattern, dip, or texture that enhances understanding of the sample.

While stereo microscopes can provide a useful magnification of up to 100x, practical use typically involves observations made with magnification between 4x and 40x.

These types of forensic microscopes also support greater working distances than other alternatives, permitting more room for manipulating and positioning the sample. Some microscopes include features such as illumination options or built-in or attachable cameras and screens, allowing researchers to view samples in varying ways or capture images or videos of samples for documentation or to share with others.  Most of these options are available as accessories, too.

Numerous applications in forensics exist for stereo microscopes. They include, but aren't limited to:

• Gunshot residue (GSR) and primer residue examination: Forensic scientists can use stereo microscopes to examine trace evidence ranging from bullet fragments to gunpowder patterns. Tiny elements that are unseen by the human eye can fill in the blanks in forensic puzzles under the magnification of a stereo microscope. For example, when a gun is fired, GSR creates patterns on any objects near the barrel. These patterns can help investigators link crimes to specific guns or shooters or put together a narrative about how a crime played out.
• Document examination: According to the Centurion University of Technology and Management, stereo microscopes are well adapted to examining various document traits, including overwriting, erasures, color, and ink. Investigators might, for example, compare microscopic details regarding pen strokes or the differences between paper or printing ribbons to understand when various documents were created and by whom.
• Insect identification in entomological forensics: This technology can help investigators determine the type and origin of an insect species when natural human observation fails. It may seem easy to determine the difference between a green June beetle and a red ladybug, for instance. However, if evidence includes only part of the bug or harder-to-identify eggs or larva, entomological forensics can put the puzzle together with help from stereo microscopes. Insect identification can help investigators understand the origin of evidence or what might have happened to it.

What Does the Future Hold for Forensic Microscopes?

Forensic microscopes are an integration of tried-and-true science and always-evolving technology. In the past few decades, innovations in microscope technology have transformed forensic science, allowing investigators and researchers to derive increasing amounts of accurate data from even the smallest samples.

Continuous innovation allows microscope technology to keep pace with the changing needs and demands of forensic investigations. And evolving technology will allow investigators to answer more questions, answer them faster, and answer them with greater confidence as they examine trace evidence.

Courtesy of Unitron