Coroner Coroner

"So, there's a 'burr' around the perimeter of the dripping blood."

(Probably as long as this:?)

Saying that, Lin Xinyi motioned Kudo and Sonoko to get closer, crouched down, and observed the small blood droplets on the floor closely.

Sure enough, they all noticed that around those round blood droplets, there were "thin blood needles" visible to the naked eye in the shape of stars, protruding in all directions.

At this time, Lin Xinyi further added:

"Let's take a closer look. Are the burrs of these blood droplets mostly long on one side and short on the other?"

"Really... Although it's not obvious, you can still see that the burrs on the left and right sides of a blood drop are not the same length."

Miss Suzuki sighed as if she had discovered a new world:

"why is that?"

"Because these blood droplets are all dripping while the murderer is in motion."

Lin Xinyi explained carefully:

"A blood droplet that drips vertically in a static state has a relatively uniform size and length of burrs around it."

"But the murderer was walking towards the toilet cubicle, and the blood droplets that fell on him would have a horizontal acceleration."

"When the drop of blood falls to the ground, the blood condenses more in the direction the acceleration is pointing, and the burr in that direction is longer."

"That is to say..."

Lin Xin paused for a while, and explained with emphasis:

"The side with the long burr is the direction of the murderer's movement at that time."

"For example, the long burr of this blood drop pointed to the toilet cubicle, which proved that the murderer was indeed carrying a blood-stained knife and walked in the direction of the toilet cubicle."

"This..." Suzuki Sonoko was a little dazed:

"What's the use of knowing this?"

"The murderer went to the toilet cubicle to throw the murder weapon and gloves after killing people. Isn't this the conclusion that Kudo has already reasoned?"

"No...it's useful."

It was Kudo Shinichi who denied it.

He stared at the ground carefully, his eyes extremely focused:

"I know what Mr. Lin Xinyi means."

"The direction of the long burr on the blood drop can show the direction of the murderer's movement at that time."

"And the blood drop here..."

Kudo Shinichi pointed to a special blood drop on the ground:

"Not all the blood droplets are burrs pointing towards that toilet cubicle."

"There are several blood droplets, and the burrs on the edges are pointing... in the exact opposite direction of the other blood droplets!"

"Er?" Suzuki Sonoko couldn't keep up with the rhythm.

"Remember, the long burr of the blood drop pointed in the direction of the murderer's movement at the time."

Looking at Miss Sonoko who was a little dizzy, Lin Xinyi once again emphasized this knowledge point:

"And several of these blood droplets have long burrs pointing in opposite directions, indicating..."

"These blood droplets are not like other blood droplets, they did not fall on the killer's way to the toilet cubicle."

"They dripped on the way back from the killer's exit from this toilet cubicle and back to the sink, so the burrs are in the exact opposite direction of the other blood droplets."

"That is to say..."

"After the murderer left the murder weapon in the compartment and the gloves down the toilet..."

"There is still blood falling from him!"

"The blood dripping at this time is not on the gloves and the murder weapon at all, but directly on the murderer's body."

Finally, Lin Xinyi earnestly concluded:

"So, it's not hard to imagine that the gloves didn't completely block the blood gurgling from the deceased at that time."

"The blood must have flowed onto the murderer's arm, and as long as we find the person whose arm is stained with the blood of the deceased, we can confirm who the murderer is."

"indeed so…"

"but…"

Kudo quickly found the loophole for Lin Xinyi's idea:

"After that guy dropped the murder weapon and gloves, he should have gone to the sink to wash his arm."

"Otherwise, if his arm is stained with conspicuous blood, it may be difficult for him to blend in with the crowd."

"it does not matter."

Lin Xinyi smiled very calmly:

"It doesn't matter how clean his hands are."

"As long as it's really bloody, I'll definitely be able to find him!"

Chapter 43 Another Approach

"Mr. Lin Xinyi, can you find the cleaned blood?"

Suzuki Sonoko asked impatiently.

Unconsciously, the eldest lady who came to "Chasing the Stars" also put herself into the identity of the investigator, and completely focused on the case.

This sense of participation has never been seen before.

Because Lin Xinyi relies on knowledge to solve the case, rather than relying on his own IQ that is different from ordinary people like those famous detectives.

IQ is a gift from God, but knowledge can be mastered by ordinary people.

Therefore, at this moment, even Suzuki Sonoko, who is an ordinary person, will have a sense of participation in "I can understand" and "I understand too"——

Instead of the estrangement and confusion of "understood what" and "you understand again" when seeing Kudo Shinichi solving the case in the past.

"Won't the blood be washed away by the water??"

Like a studious student, Suzuki Sonoko added.

"It's just superficially clean."

"There are still traces of undetectable residual blood after washing, and through scientific means, such as the luminol reaction, we can find it."

Lin Xinyi explained:

Luminol, also known as luminol, emits blue light when oxidized.

The heme in the blood can catalyze the reaction between luminol and hydrogen peroxide, showing blue-green fluorescence.

The assay is so sensitive that it can detect even trace amounts of blood diluted to one part per million.

Therefore, it is basically impossible to escape the detection of Luminol by washing with water.

If you really want to clean up the traces, you must first destroy human DNA with a strong oxidant such as hydrogen peroxide, then rinse the scene with animal blood, cover it, and finally rinse it again with bleach.

And the prisoner hurriedly escaped from the scene, and was immediately trapped on the platform. He had absolutely no conditions to clean up the traces so thoroughly.

"Lumino..."

Kudo Shinichi, who was on the side, reacted after a while:

"Yes...there is indeed such a thing."

"But I don't seem to have seen the Metropolitan Police use it before..."

He suddenly remembered that he had also learned this knowledge point in Hawaii.

It's just that so many cases have been solved... Whether it is him, other detectives, not to mention the police, basically no one has used this kind of technical means.

Unconsciously, this thing was almost forgotten by everyone.

"Uh? Haven't seen the Metropolitan Police use it?"

Lin Xinyi felt his scalp go numb when he heard:

Luminol has been used for criminal investigation blood tests since the 30s. The Metropolitan Police Department is not equipped yet, right?

No... At the level shown by the Metropolitan Police in this world, it is possible that it is equipped and not intended to be used.

Otherwise, if they can use all the criminal science and technology that the police should have, there is no such thing as a detective.

"I hope the Metropolitan Police Department can be more reliable this time..."

"At least the most basic survey tools should be prepared."

Lin Xinyi sighed helplessly in his heart.

Then, planning to use the Luminol reaction blood test, he came out of the crime scene with Kudo and Sonoko to the platform outside.

At this time, Lin Xinyi discovered that...

The real difficulty in investigating the case does not lie in technical equipment, but in people, that more than 100 people who were forced to stay to cooperate with the investigation.

Lin Xinyi and three people just came out of the bathroom, and the waiting passengers who were guarded on the platform and not allowed to leave immediately looked over:

"Come out, come out!"

"Have you found out who the murderer is?"

More than 100 pairs of eyes looked over at the same time, and their eyes were basically full of impatience.

"Uh...not yet."

"But we have found a way to locate the murderer. When the technicians from the Metropolitan Police Department come over, we can find out who the murderer is."

It was Kudo Shinichi who stood up and spoke. He was more famous and more prestige in front of the masses.

But this time, even the prestige of the great detective won't work: