Forensic drug detection apparatus. A gas chromatography machine (left) connected to a mass spectrometer (right) in a forensic laboratory. This equipment is sensitive enough to detect minute quantities of illegal drugs in the hair of a suspect - weeks after any drugs were taken. A sample injection robot (left) transfers samples from small vials to the chromatography machine, where the samples are evaporated and separated according to molecular weight. The spectrometer identifies even minute traces of chemicals as they emerge from the chromatography tube (not visible).