Forensic scientists are highly trained individuals with backgrounds in physics, chemistry, biology, toxicology and psychology. They are trained in fingerprinting and document analysis, math and problem solving, logical thinking and reasoning. They analyze pieces of evidence collected at crime scenes. Complex instruments, computers and sophisticated computer programs, powerful microscopes and reference materials are at their disposal to help make careful analyses and arrive at conclusions.
Microscopes are utilized greatly in a forensic laboratory to examine evidence. A high-power compound forensic comparison microscope is used for side by side split screen analysis and comparison of minute specimens. Specimens with opaque and polished surfaces, like glass, ceramics, coal and leather, are analyzed with a metallurgical metallographic epi illumination forensic comparison microscope. Scientists use a low-power stereoscopic comparison microscope when comparing ballistic fingerprints on guns and bullets and examining larger specimens like wire, fabric, carpeting, handwriting or fingerprints that do not require higher magnification.
Chemistry is used to analyze urine, blood and other body fluids, dyes, stains, toxins and drugs. A forensics laboratory can have a gas chromatograph for analyzing and separating compounds and mass spectrometers for identifying molecules present in gases, liquids and solids. Forensics labs use fume cupboards to minimize exposure of scientists to hazardous vapors, dust and fumes, and ultrasonic cleaners to clean the tools used for collecting and examining evidence.
Forensic scientists use various tests and chemicals in analyzing different body fluids. They use the Kastle-Meyer test, a presumptive test, which uses phenolphthalein to detect the presence of hemoglobin, and determine whether a sample is blood. Blood turns pink when it comes in contact with phenolphthalein. Anti-A or anti-B antibodies, collectively called antisera, are used to identify blood groups. The chemical luminol is sprayed on evidence and crime scene areas to identify blood traces and get samples. PCR or polymerase chain reaction system is used for DNA typing.
There is usually evidence that cannot be seen by the naked eye. An ultraviolet lamp is helpful in revealing invisible signs like dried semen stains, areas that have been cleaned to remove evidence of a crime, and other traces of evidence too faint to be easily detected. Forensic scientists wear special goggles when using ultraviolet lamps.