Luminol Law and Legal Definition

Luminol is a chemical containing carbon, nitrogen, oxygen and hydrogen. It is used by crime scene investigators to detect blood at crime scenes where no blood is visible. The chemical glows greenish-blue when it comes into contact with blood by reacting to hemoglobin, an oxygen-carrying protein in red-blood cells. It is very sensitive and can be used to detect traces that are years old and can detect blood at 1 part per million.

Luminol also reacts to some metals, paints, cleaning products and plant matter. However, the chemical reacts differently to different substances. For example, metals cause an immediate glow that quickly fades, while blood glows longer. A specialist analyzes the reaction, and then performs more conclusive tests to determine whether the blood is human.