Investigators spray an area with luminol. Then they turn out the lights, black out the windows, and look for a bluish-green light. If there are any traces of blood in that area, they will glow.
When hemoglobin and the luminol mixture come in contact with each other, the iron in the hemoglobin accelerates the reaction between the hydrogen peroxide, which is in the liquid with which the luminol powder is mixed. This creates a reaction call an “oxidation reaction,” and this reaction creates an energized state. Because the iron in the hemoglobin accelerates the process, the light is bright enough to see in a dark room. This is as simplified as I can get in explaining this process, but it all boils down to a chemical reaction with the end result of lighting up the blood particles in the dark.
When an investigator finds evidence of blood traces with the luminol, he/she will photograph or videotape the crime scene. As a general rule, luminol only shows that there might be blood in an area. There are other substances, such as household bleach, which can light up luminol; however, experienced investigators can reliably make an identification based on how quickly the reaction occurs and further tests can be done to determine whether or not it really is blood.
Luminol is a great investigative tool. It can help determinate the point of attack and what type of weapon was used. This is because a bullet makes blood splatter differently than a knife does. It can also reveal faint bloody shoe prints, giving the investigator information about what the killer/attacker did after the attack.
The one problem with luminol is that it can destroy other evidence in the crime scene. For this reason, crime scene investigators use other tools first and explore the crime scene before spraying luminol.
Though a great investigative tool, using luminol does have its drawback and is not used as frequently as we may think. On the other hand, a writer can do some interesting things to his/her story by bringing this tool into the investigation.
Faye M. Tollison
Author of: To Tell the Truth
Sarah’s Secret
Member of: Sisters in Crime
Writers on the Move
