Chemical tests have been used for decades to help crime scene technicians determine what evidence may be present. Luminol is one of those chemicals and it is used to identify suspected trace evidence pieces that could have blood on them. It has been used from crime scene evaluation since it was first introduced to forensic science in 1937.
Luminol isn’t the only chemical that can be used to determine if a red speck is blood or not. It is, however, the one chemical that creates a certain luminescence when it is exposed to blood. This makes it much easier to spot blood evidence to be collected.
Luminol Provides Numerous Advantages
There are a number of advantages that Luminol provides those who are searching for blood evidence at a crime science. This is because the chemical is so sensitive to blood that it can detect blood at levels of just 1 part per million.
1. It is Non-Corrosive.
It can be sprayed over most surfaces quickly and easily and it won’t stain after it settles onto the surface or cause corrosion.
2. It Maintains the Integrity of the Evidence.
Luminol does not prevent various testing systems from being conducted on blood that is found. This includes blood typing tests and enzyme typing.
3. It Shows Blood When the Human Eye Cannot.
When sprayed over a large area, even small droplets of blood can become visible. It will also show patterns of blood wiping that occur when a crime scene has been cleaned up. For certain crime scenes, Luminol can even be used to track footprints, drag patterns, and other activities that have caused blood samples to spread.
There’s also the fact that the results of Luminol can be directly photographed so that they may be properly presented as evidence in a court of law. The end result is that forensic technicians using Luminol follow procedures that have met legal and scientific standards for evidence.
What Are the Disadvantages of Luminol?
Although brightly glowing specks of blood can be detected thanks to Luminol, there are a number of additional small particles that will also glow when they encounter this chemical. Bleach, vegetable peroxide, horseradish sauce, and certain metals will also reflect. This means forensic technicians must test each glowing area to determine if it is actually blood or some other substance. Without secondary verification, the results will not typically withstand legal scrutiny.
The light of Luminol only works in darkness as well, which means that all work within a crime scene must stop after the chemical has been sprayed so results can be collected and photographed. The darkness also makes it difficult to properly photograph the evidence. Modern digital videography allows for a recording to be made of the Luminol reaction instead, which is easier to complete, but still requires a processing pause.
For this reason and because of the fact that Luminol may destroy certain other types of non-blood evidence, the entire scene will generally be processed before the spray is applied to the area. That means TV forensics gets some of it right, but some of it is very wrong.
Luminol Glows Because of Its Catalyst
Blood has iron within it, which is why the Luminol is able to glow once it encounters it. An oxidation reaction occurs and the Luminol loses nitrogen and hydrogen in order to gain oxygen. This creates an energized state which then creates the glow which can be photographed or recorded in a dark room. It is a reaction that is similar to the bio-luminescence that can be seen in certain plants and animals.
To say that Luminol can solve a case would be inaccurate. It often leads investigators to other clues which can help to piece together the puzzle of a case. Blood splatters in different patterns for different reasons, a fact forensic science has verified, and Luminol can highlight the splatter. Blood found on the carpet thanks to Luminol can be removed so that more evidence and even visible blood can be found on the sub-flooring beneath it.
The Luminol blood test helps law enforcement officials be able to track down someone who might have thought they had been able to cover their tracks. Although the chemical will glow when exposed to other substances, it is a wonderful first-use detection tool to help investigators determine if further testing is needed. It has helped put away bad guys for more than seven decades and continues to be a useful tool in forensic investigations.