During the testing, everyone except Fujino was sent back to their rooms.
Since no DNA comparison was needed, the results came back almost immediately.
Not one of the knives they had found showed a fluorescent reaction to blood.
Officer Yamamura looked puzzled. "None of these knives show any trace of blood. Did the killer hide the knife somewhere?"
Fujino chuckled beside him. "Or maybe they've all been cleaned."
"Huh? What do you mean?"
Officer Yamamura blinked, confused.
Luminol reagent was one of their most useful forensic tools.
Couldn't find the crime scene?
Spray some Luminol reagent...
Couldn't identify the murder weapon?
Spray some Luminol reagent.
They didn't use it often, but it really came in handy when it mattered.
Still confused, he asked, "I've never heard of cleaning it off. Luminol reagent detects the iron in blood, and it's incredibly sensitive. Even a tiny trace of blood will glow when it comes into contact with the reagent..."
"That's true."
Fujino was fairly pleased with Yamamura's grasp of the theory.
Yamamura might be a bit hopeless, but he understood the basics of forensic testing.
Otherwise, how would he have become a police officer and passed the civil service exam?
So Fujino explained, "Blood can be washed out of clothing with alcohol, toothpaste, and cold water. Blood on objects can also be removed with toilet cleaner or lingerie detergent."
Yamamura looked even more baffled. "Why?"
"Because blood is mainly made up of blood cells and plasma, and it's the hemoglobin that causes the luminol reaction..." Fujino explained. "Cold water keeps proteins from setting, alcohol breaks them down, and toothpaste scrubs dirt, grease, and suspended particles from fabric. Once the hemoglobin is destroyed, there's no luminol reaction."
"The same goes for toilet cleaner. Its strong acid breaks down protein structures, while lingerie detergent