The murderer had finally surfaced.
The man wore an utterly ordinary short-sleeved shirt and jeans, with a somewhat worn but clean messenger bag slung around his waist. He did not look like a murderer at all—rather, he looked like a young office worker passing by.
No one would have noticed someone as ordinary as him in a crowd.
But at this moment, he was like salt dissolved in water, crystallized by the blazing sun of justice.
More than a hundred pairs of eyes at the scene locked onto him in unison, leaving him nowhere to hide.
"I..."
The young man whom Lin Xinyi had identified as the murderer looked somewhat stiff.
But in the end, his response was:
"Are you kidding me?!"
"You're calling me the murderer because of a few flies? I ate ice cream not long ago, and some frosting from it got on my hands. Isn't that perfectly normal?"
The young man defended himself with great agitation.
"Heh." Lin Xinyi gave him a disdainful smile.
Indeed, using flies to seek out blood had severe limitations and was easily disrupted.
Common things like frosting, cream, and honey could all attract flies. Flies gathering around someone did not necessarily mean that person had blood on them.
Things were different now from ancient times.
Back then, flies seeking blood could make murderers confess, probably because—
If they refused to confess, they would be dragged back to the magistrate's office and beaten.
With torture devices like finger clamps and tiger benches brought out, who could hold out without confessing?
That was not even to say the investigator had been unethical.
After all, an investigator who thought to use the scientific method of flies seeking blood rather than directly dragging several suspects who held grudges against the victim away for brutal interrogation—
In feudal society, that already counted as the spirit of the rule of law shining brightly.
Ancient times had "convenient" methods, but modern investigations were more "troublesome."
Modern cases required evidence, and flies were far from reliable evidence.
However—
Lin Xinyi had never intended to use flies as conclusive evidence pointing to the murderer.
Flies seeking blood was merely a screening method he had used under pressure and with limited time, to quickly narrow the suspects down from more than a hundred people.
By his reasoning, there might have been several passengers in the crowd capable of attracting flies.
But that did not matter. As long as those few passengers surrounded by flies were kept behind and brought to the Tokyo Metropolitan Police Department for Luminol tests one by one, they could further determine who the murderer was.
And now, out of more than a hundred people, there was only one person the flies liked.
There was no need to wait for the next round of test results. The murderer was basically him.
"Stop resisting."
"Whether you have blood or frosting on you, science will tell us the answer."
Lin Xinyi could tell at a glance that this suspect probably did not even know Luminol existed, which was why he still held onto that tiny bit of hope.
So, he simply explained the Luminol reaction to everyone again.
"A reagent that can find diluted bloodstains?"
Upon hearing that, the young man's voice trembled slightly.
But after his eyes flickered for a moment, he still answered steadily and clearly:
"That still doesn't prove anything!"
"I had a nosebleed this morning, and I wiped it with my hands."
"So even if you find blood on me, that can't prove I killed anyone, can it?"
The more he spoke, the firmer his tone became. By the end, he even wore an indignant expression, as though he had truly suffered some outrageous injustice.
"That's simple."
The speaker was not Lin Xinyi, but the great detective Kudo, whom everyone had nearly forgotten:
"Now that we've identified the murderer, finding evidence won't be difficult."
"The murderer's goal at the time was robbery, and all the cash in the victim's wallet has vanished."
"The victim's cash is most likely still on the murderer, so as long as we send all the bills on you for testing and check for fingerprints or skin flakes left by the victim, we can confirm whether you're the murderer!"
Kudo Shinichi stepped forward with a confident expression.
He had never played one-against-a-hundred before, but now that it was one-on-one, this should have been his specialty.
Yet the young man considered the murderer instead revealed a smile that said, "I knew it."
"That makes sense!"
"Then investigate me—this is all the money I have on me. Take it all and test it!"
"If you can't find any fingerprints or skin flakes, you'll have to kneel and apologize to me!"
As he spoke, he directly took several pitifully low-denomination coins from his messenger bag and displayed them openly before everyone.
"This..." Kudo Shinichi's smile froze.
The murderer had clearly prepared for this.
He had most likely realized that he might be investigated after being forcibly trapped at the scene.
So, he had secretly hidden the stolen money somewhere inconspicuous on the platform, planning to find a way to retrieve it after the investigation was over.
Maybe it was in a trash can, maybe in a vending machine. In any case, he definitely had none of the bills stolen from the victim on him now.
And judging by how prepared and fearless he looked, he had probably handled the bills wrapped in his clothes. Perhaps he had not even left his own fingerprints on them.
This bastard...
Instead of using his brain to devise a more complicated murder trick, he had put all his effort into cleaning up evidence.
How could you be this un-Conan-science?
Heisei Holmes felt somewhat depressed.
This truly was the kind of criminal he had never dealt with before, and he was unexpectedly troublesome.
"No... there's no way this guy covered every possible angle!"
"If we observe carefully, we might still find a breakthrough."
Kudo Shinichi steeled himself, ready to engage the criminal in a battle of wits.
But Lin Xinyi spoke again:
"Um..."
"Do we really need to look elsewhere for evidence?"
"Do you think diluted and washed bloodstains can't be tested for DNA, and that only bloodstains visible to the naked eye can be tested?"
"Do you think that if there's so little blood the naked eye can't see it, forensic experts can't extract and test it?"
Lin Xinyi spoke with a strange expression.
"Huh?" The young man's face changed. "What... what are you talking about..."
"Even such tiny traces of blood... can still be tested for DNA?"
"Of course."
Lin Xinyi looked at the murderer as though he were a clown putting on a poor performance.
"DNA extraction and purification from trace samples has always been a key area of forensic evidence research."
"And the Luminol reaction does not interfere with DNA extraction."
"So, as long as we perform a Luminol latent blood test on you, then collect a sufficient amount of bloodstained skin flakes from the areas emitting blue fluorescence, we can easily determine whose blood it is."
Latent blood samples contained extremely small amounts of blood. Conventional DNA extraction methods were limited by the volume of the carrier and could not obtain enough template DNA for PCR amplification, so it was indeed difficult to achieve good DNA profiling.
But that was not a problem at all. DNA purification and extraction techniques for trace samples could be of great help.
For example, Magnetic Bead Method nucleic acid purification technology used nanoscale magnetic beads. The surfaces of these beads were marked with a functional group capable of adsorption reactions with nucleic acids.
There was also column purification. The nucleic acid purification columns used in this technique employed silica membranes as specific adsorbent material for nucleic acids, while barely adsorbing other biological materials. This ensured maximum recovery of DNA\RNA from the sample while removing other impurities.
In the future, these technologies would mature enough to be made into ready-made purification and extraction kits. One would only need to buy them and follow the instructions step by step.
Of course, Lin Xinyi was not entirely sure whether these technologies had been put into use in 1996.
Come to think of it, DNA testing had only begun to be used in criminal investigations in 1984. DNA purification technology might still have been frontier technology that had not yet entered practical use.
"I should find an opportunity to learn from Miyano Shiho..."
"She's a biologist. She should understand this better than I do."
Lin Xinyi merely used technology; he did not research it.
Just as an excavator operator probably did not know much about the development history of excavators, he truly did not know much about this subject.
But even if it had not yet been put into use, it did not matter. At worst, they could collect the bloodstained samples from this murderer and store them for testing ten years later.
Biological science would develop rapidly over that period. By the beginning of the twenty-first century, testing methods for trace bloodstains invisible to the naked eye would certainly have matured.
And Japan's statute of limitations for criminal prosecution was fifteen years. This bastard would never escape legal punishment.
It was only that this would allow the murderer to remain at large for a long time.
Justice delayed was likely difficult to call justice at all.
So, Lin Xinyi simply ignored whether these technologies had matured yet. He merely put on an expression that said, "You're dead," and spoke coldly to the young man:
"Idiot, and you're still trying to hold out with knowledge like that?!"
"You probably have no idea, do you—"
"As long as forensic experts remove the bloodstained skin flakes emitting blue light from your body and place them in a beaker, add digestion solution for incubation, then extract, run them through a column, and wash them, they can repeatedly pass the large volume of digestion solution through the purification column, concentrating the limited DNA in the digestion solution onto the column membrane."
"Finally, they can add a small volume of pure water for elution and obtain high-quality, high-concentration DNA."
To make it more convincing, Lin Xinyi even explained the detailed procedure:
"Then the police will naturally determine whose blood is on you."
"And if the blood found on your hands belongs to the victim..."
"Heh, do you think you'll still have any room to argue?"
"I... I..."
The young man's face turned deathly pale.
He had indeed never heard of any scientific technology capable of testing DNA from latent blood, nor did he know whether such technology actually existed.
But hearing Lin Xinyi go on at such length, saying things that sounded so professional—
Being uneducated, he could only believe him.
At that thought, the man began to sweat coldly without realizing it.
His body tensed nervously as he unconsciously backed away.
"You still want to run?"
Lin Xinyi frowned slightly.
Mouri Ran clenched her fists, producing a sharp cracking sound.
"I..."
The young man's eyes were full of unwillingness.
But when he recalled the wall shattered beside the stairway, he still stopped with an ashen face.
"I confess."
Before you continue