ABSTRACT
Another presumptive test for the presence of blood is the use of luminol, a chemical that glows greenish blue when it reacts with blood. Luminol can detect highly degraded blood or minute samples. Investigators typically use luminol at crime scenes to reveal bloodstains that have been washed out, wiped off, or not visible to the naked eye. The chemical is sprayed over the area to reveal blood, and the chemiluminescence is observed in total darkness. Luminol has been reported to be so sensitive that it can detect as little as 0.2-10 parts per million, or (on average) 1 drop of blood within a container of 999,999 drops of water. Photographs are taken to obtain a permanent record of the test results.
