Luminol was first used to analyze a crime scene in Germany in 1937. Since then, it has become a very popular tool for Crime Scene Investigators (CSIs) to use to reveal blood stains at a crime scene because of its extreme sensitivity to metal catalysts and its affordability. Even the world's best criminal has a difficult time
cleaning all traces of blood at their crime scene. A basic
luminol solution combined with hydrogen peroxide and a thickening agent can be sprayed on surfaces with suspected blood traces. The solution will glow if catalyzed by the presence of a metal ion, such as iron in blood hemoglobin. The iron can be in a concentration as small as 1 part per million for the luminol to glow. CSIs will then either photograph or videotape the area since luminol will only glow intensely for 10 seconds. This piece of evidence can help determine the point of attack, blood splatter patterns, bloody shoe prints, drag marks, or weapon prints.
There are a few problems with using luminol, however. First, luminol is only a presumptive test. It can lead the CSIs to investigate a particular area further but it cannot positively confirm the presence of blood and will not be allowed to prove such in a criminal investigation. Luminol can be catalyzed by substances such as bleach, copper, potassium permanganate (found in many dyes), saliva, brain tissue, bone marrow, rust, and vegetable enzymes. These can make luminol glow and creates a "false positive" test for blood. Secondly, luminol can destroy some genetic markers in cell DNA. It should not be used if the evidence needs to be preserved for genetic analysis. Thirdly, it can smear bloody impressions and make prints and splatters more difficult to analyze. This can be decreases by adding a thickening agent to the luminol solution.
Luminol (and similar compounds) have been profitable for many people and businesses. It is used and sold as an emergency light source for vehicles, businesses, schools, and the military. Glowsticks are occasionally made using luminol, which are sold at many events.
They are always a popular item at Halloween time to keep children safe while trick-or-treating.