What is the primary use of luminol in crime scene investigations?

Luminol is primarily used in crime scene investigations to detect traces of blood that may not be visible to the naked eye. This compound reacts with the iron in hemoglobin found in blood, producing a luminous blue glow when it comes into contact with blood, even in very diluted forms. This quality makes luminol an invaluable tool for investigators, enabling them to identify potential bloodstains in areas where visible evidence might be sparse or completely absent.

While luminol can help illuminate areas in a way, that is not its main purpose; its effectiveness is specifically rooted in its chemical reaction with blood. This capability is crucial in cases where blood has been cleaned up or when investigators are trying to locate blood at a crime scene that may not be immediately apparent due to lighting conditions or other factors.