From a Forensic scientist’s point of view, few instruments present in a crime laboratory can match the versatility of the forensic comparison microscopy. The forensic comparison microscope’s magnifying power is an essential necessity for searching and finding very small traces of physical evidence. Once found, many items of physical evidence may be characterized by a forensic comparison microscopic examination of their morphological features. Likewise, the forensic comparison microscopy can be used to study how light interacts with the material under investigation, or it can be used to observe the effects that other chemical substances are having on such evidence. Each of these features will allow the forensic examiner to better characterize and identify physical evidence. Recently, by attaching it to a computerized spectrophotometer, a new element has been added to the capability of the forensic comparison microscope. This combination has given rise to a new instrument called the microsectrophotometer.
In many respects, this is an ideal discovery from the forensic scientist’s viewpoint. The chemist can take advantage of the selective absorption of light materials in order to characterize them. In particular, light in the ultraviolet, visible, and infrared regions of the electromagnetic spectrum has proved mot helpful for this purpose. But sadly in the past forensic chemists were unable to take full advantage of the capabilities of spectrophotometry for examining trace evidence, as most spectrophotometer are not well suited for examining the very small particles commonly encountered as evidence. However, with the development of the microspectrophotometer, a forensic analyst can now view a particle under a forensic comparison microscope while, at the same time, abeam of light is directed at the particle in order to obtain its absorption spectrum. Depending on the type of light employed, an examiner can acquire either a visible or an IR spectral pattern of substance being viewed under the microscope. The obvious advantage of this approach is to provide the forensic scientist with added information that will characterize trace quantities of evidence. A microspectrophotometer designed to measure the uptake of visible light by materials.
The visual comparison of color is usually one of the first step in examining paint, fiber, and ink evidence. Such comparisons are easily obtained by means of a forensic comparison microscope. Now, with the use of microspectrophotometer, not only can the color of materials be compared visually but, at the same time, an absorption spectrum can be plotted for each item under examination to display the exact wavelengths at which it absorbs in the visible light spectrum. Sometimes, colors that appear similar by using the visual examination will show significant differences in their absorption spectra. The microspectrophotometer is used to distinguish counterfeit and authentic currency by comparing the spectral patterns of inked lines on currency.
Another emerging technique in forensic science is the utilization of the infrared microspectrophotometer for the forensic comparison examination of fibers and paints. The “fingerprint” IR spectrum is unique for each chemical substance. Therefore, if such a spectrum can be obtained either a fiber or a paint chip, it will allow the analyst to better identify and compare the type of chemical from which these materials are manufactured. With a microspectrophotometer, a forensic analyst can view a substance by means forensic comparison microscopy and at the same time have the instrument plot the infrared absorption spectrum for that material. Read more on this subject