Spectroscope, Circa 1920. A spectroscope is an instrument for producing and observing spectra. In the 1890's scientists began using spectroscopy for medical research and criminal investigations. The field of toxicology was the first to benefit. Late 19th-century forensic pathologists were enthusiastic about the potential uses of spectroscopic analysis to detect the presence of carbon monoxide and other poisons in blood. A small specimen of blood, diluted in water, absorbed light of certain colors and could be subjected to spectroscopic analysis. This analysis could reveal the presence of carbon monoxide and other poisons.