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Luminol Was First Created in 1902 - But How Does It Work?

© 2015 (updated 2020), Stephanie Hoover - All Rights Reserved. Permission Required for Re-Use or Distribution.

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Glowing Puddle of Luminol
The famous blue glow of Luminol.

You're watching your favorite crime scene investigation show. It's the point in the story where the suspect has been led away in handcuffs. The stone-faced crime tech hurries into the perp's bedroom. He pulls a small spray bottle from his lab coat pocket. He pumps the top once or twice and, within seconds, the entire wall glows a brilliant blue. He casts a knowing glance at the detective who declares, "It was a bloodbath in here." The camera zooms in on the real star of the scene: the bottle of luminol, still in the crime scene tech's capable, gloved hand.

While this scenario may play well in the fictional world of crime TV, true forensics experts know it's malarky. Does luminol detect blood? Of course. Does it immediately signify whose blood? Not a chance. And what about that blue glow? Well, maybe the suspect was a heavy cigar smoker. Or really liked horseradish.

As everyone reading this article knows, luminol exhibits what the scientists call "chemiluminescence." That's a fancy way of saying that it glows blue when reacting to hemoglobin and other substances.

Reportedly first synthesized in 1902, it was not until 1928 that a German chemist first studied and recorded luminol's peculiar reaction to blood. Another German, forensic scientist Walter Sprecht, first tested it at crime scenes in 1937.

According to a document created by the National Criminal Justice Referral Service, luminol was first proposed for American forensic applications in 1942. It took some time for police departments to accept - not to mention understand and afford - luminol and its attendant training and equipment requirements.

Many Americans first learned of luminol during the murder trial of Dr. Sam Sheppard. The Sheppards were a wealthy family living in the toney, lakeshore suburb of Cleveland known as Bay Village. The doctor's wife, Marilyn, was bludgeoned to death in the early morning hours of July 4, 1954.

Dr. Sheppard told a story that police found suspicious. He'd fallen asleep on the daybed in the living room, Sheppard said, and was awakened after 3 a.m. by the screams of his wife. Sheppard ran upstairs to the couple's bedroom only to be intercepted by a tall man he described as having "bushy hair." The intruder struck Sheppard with a heavy object, rendering him temporarily unconscious. The doctor's next recollection was of waking up on the shore of Lake Erie.

Marilyn's murder was particularly violent. She'd been struck 27 times by an unknown object. The force and viciousness of the blows rendered her nearly unrecognizable. Blood spatter covered the walls of the bedroom, but blood droplets were also deposited elsewhere in the home. These were identified and tested by Henry Dombrowski, a member of the Cuyahoga County Scientific Identification Unit.

Dombrowski was known as a "blacklight man" because he used ultraviolet light to study crime scenes. During Sheppard's first trial, he testified about his use of luminol in the Sheppard home and his subsequent findings. Asked by prosecutors to explain luminol to the jury, Dombrowski said:

"It is a testing re-agent that can be sprayed onto suspected blood spots. It is used in total darkness, and when it is sprayed on a blood spot, the blood will then cause the luminol solution to glow - give it a sort of bluish-greenish fluorescence."

In a time that pre-dated today's high-tech forensic techniques and DNA analysis, this seemed like science fiction to many trial watchers.

Challenges to luminol evidence are sometimes valid. Common household items like bleach can trigger false positives, as can certain vegetable matter like the aforementioned horseradish. Residue from heavy cigarette and cigar smoke can also affect results.

Luminol, by the early 1990s, became a standard tool for forensics teams in even small police departments. It is, unquestionably, the most reliable indicator of the presence of blood. Early luminol adopter and forensics expert Gary A. Rini famously promised it can indicate one drop of blood in five million drops of water.

What luminol can't do is immediately identify the victim or killer, nor can it solve every crime on every television network - or in real life, for that matter.

Want to test it for yourself? Contrary to popular belief, luminol sales are not restricted to law enforcement personnel. In fact, you can buy it online for less that the cost of a good lunch for two.

Lab coats sold separately.

Try Luminol Yourself:

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