Suffering from a Lack of Culture

The killer finally surfaced.

The man was dressed in a very ordinary short-sleeved shirt and blue jeans, with a slightly worn but clean shoulder bag slung over his waist. He didn't look like a murderer at all; he looked more like a young office worker passing by.

No one in a crowd would ever notice someone as unremarkable as him.

But at this moment, the man was like salt dissolving in water, precipitating out under the righteous sun.

Over a hundred pairs of eyes locked onto him in unison, leaving him nowhere to hide.

"I..."

The young man, whom Lin Xinyi had identified as the killer, looked somewhat stiff.

But in the end, his response was:

"What kind of joke is this?!"

"You're saying I'm the killer just because of a few flies? I just had ice cream a while ago, and some frosting from it got on my hand. That's perfectly normal, isn't it?"

The young man passionately defended himself.

"Heh." Lin Xinyi gave him a disdainful smile in return.

Indeed, using flies to detect blood has significant limitations and is very easily interfered with.

Common substances like frosting, cream, or honey can also attract flies. The presence of flies doesn't necessarily mean there's blood on a person.

The present is different from ancient times.

In ancient times, using flies to find blood could make a killer confess, probably because...

If they didn't confess, the killer would be taken back to the yamen and beaten.

With torture devices like finger-crushers and tiger-benches, who could endure without confessing?

And it couldn't be said that the official wasn't upright.

After all, for that official to think of using the scientific method of flies to find blood to investigate a case, instead of directly taking the suspects who had grudges with the deceased back for brutal interrogation—

In feudal society, that was already considered the spirit of the rule of law shining brightly.

Ancient times had "convenient" methods, but modern times are more "troublesome."

Modern investigations require evidence, and flies are far from being reliable evidence.

However...

Lin Xinyi had never intended to use flies as conclusive evidence pointing to the killer.

Using flies to detect blood was merely a screening method he resorted to under duress and time constraints, to quickly identify a suspect from over 100 people.

According to his plan, there might be several passengers in the crowd who could attract flies.

But this didn't matter; he only needed to keep the few passengers with flies around them, take them to the Tokyo Metropolitan Police Department, and perform Luminol presumptive blood tests on them one by one to further confirm who the killer was.

And now, out of over a hundred people, there was only one person who was "liked" by flies.

Without even waiting for the next test results, he was almost certainly the killer.

"Don't resist stubbornly anymore."

"Whether what's on you is blood or frosting, science will tell us the answer."

Lin Xinyi could tell at a glance that this suspect probably had no idea about the existence of Luminol, and thus still held a glimmer of hope.

So, he simply took the opportunity to explain what the Luminol reaction was to everyone present.

"That can... it can find diluted bloodstains?"

Hearing this, the young man's voice trembled slightly.

But after a flicker in his eyes, he still responded calmly and clearly:

"That doesn't prove anything!"

"I had a nosebleed this morning, and I wiped it with my hand."

"So even if blood is found on me, it can't prove I killed anyone, right?"

The more he spoke, the firmer his tone became, and by the end, he even put on an indignant expression, as if he had truly suffered some excessive injustice.

"That's simple."

It wasn't Lin Xinyi who spoke, but the great Detective Kudo Shinichi, whom everyone had almost forgotten:

"Once the killer is identified, finding the evidence isn't difficult."

"The killer's motive at the time was robbery, and all the cash in the victim's wallet also disappeared."

"The victim's cash is most likely on the killer now, so if we send all the banknotes on you for examination to see if they have the victim's fingerprints or skin cells from when they touched them, we can confirm if you're the killer!"

Kudo Shinichi stepped forward with a confident expression.

He hadn't played the "1 out of 100" game, but the current "1 on 1" should be his area of expertise.

However, the young man designated as the killer instead showed a "I knew it" smile:

"Good point!"

"Then go ahead and search—I only have this much money on me, you can take it all and search it!"

"But if you don't find any fingerprints or skin cells, you'll have to perform dogeza to apologize to me!"

With that, he directly pulled out a few coins of pitifully small denominations from his shoulder bag and brazenly displayed them to everyone.

"This…" Kudo Shinichi's smile froze:

It was clear the culprit had come prepared.

He had probably realized he might be investigated as soon as he was forcibly confined to the scene.

So, this guy had secretly hidden the stolen money somewhere inconspicuous on the platform, planning to retrieve it after the investigation was over.

It could be hidden in a trash can, or a vending machine—in short, he definitely didn't have any of the stolen banknotes from the victim on him now.

Moreover, seeing how prepared and fearless this guy was, he probably wrapped his clothes around his hands when he touched the banknotes, so he might not even have left his own fingerprints on them.

This bastard…

Instead of racking his brain for a more complex murder plot, he spent all his effort on clearing traces.

How could you be so un-Conan-science?

Heisei Holmes felt a bit dejected.

This was indeed a type of culprit he had never dealt with before, surprisingly troublesome.

"No—this guy couldn't have thought of everything!"

"Careful observation might still reveal a breakthrough."

Kudo Shinichi braced himself, ready for a battle of wits with the culprit.

But Lin Xinyi spoke up again:

"Um…"

"Do we really need to find evidence elsewhere?"

"Do you think that diluted bloodstains can't be DNA-tested, and only bloodstains visible to the naked eye can be DNA-tested?"

"Do you think that if the bloodstains are too faint to be seen, Forensic Officers can't extract and test them?"

Lin Xinyi said with a strange expression.

"Huh?" The young man's face changed: "W-what are you saying…"

"Even such trace amounts of blood, c-can they also be DNA-tested?"

"Of course, they can."

Lin Xinyi looked at the culprit as if he were watching a poorly performing clown:

"DNA extraction and purification from trace samples are precisely the focus of forensic material evidence research."

"And the Luminol reaction does not interfere with DNA extraction."

"So, as long as we perform a Luminol presumptive blood test on you, and then take a certain amount of blood-stained skin cells from the areas that show blue fluorescence, it will be very easy to determine whose blood that is."

Trace blood samples have very low blood content. Conventional DNA extraction methods are limited by the carrier volume and cannot obtain the template DNA quantity required for PCR amplification, making it indeed difficult to get good DNA typing.

But this is actually not a problem at all; DNA purification and extraction techniques for trace samples can be of great help.

For example, magnetic bead nucleic acid purification technology uses nanometer-sized magnetic beads, whose surfaces are marked with a functional group that can adsorb to nucleic acids.

Additionally, there's column purification, which uses a nucleic acid purification column with a silica gel membrane as a specific adsorption material for nucleic acids, while barely adsorbing other biological materials. This ensures the maximum recovery of DNA/RNA from the sample while removing other impurities.

These technologies will mature in the future to the point where they can be made into ready-made purification and extraction kits. All you'd need to do is buy them and follow the instructions step by step.

Of course, Lin Xinyi wasn't entirely sure if these technologies were in use in 1996.

Speaking of which, DNA testing only began to be used in criminal investigations in 1984, so DNA purification technology might still be cutting-edge science not yet applied in practice.

I should find an opportunity to learn from Miyano Shiho.

She's a biologist; she should know more than me.

Lin Xinyi was a user of technology, not a researcher of technology.

Just like an excavator operator probably doesn't know much about the history of excavator equipment development, he truly didn't know much in this area.

But even if it wasn't in use yet, it didn't matter. At worst, he could collect the blood-stained samples from this culprit and store them for 10 years before testing.

Biological science and technology would develop rapidly during this period. By the early 21st century, detection techniques for trace bloodstains invisible to the naked eye would surely have matured.

And the statute of limitations for criminal prosecution in Japan was 15 years; this bastard would definitely not escape the punishment of the law.

It would just allow the culprit to remain at large for a long time.

Justice delayed could hardly be called justice.

So, Lin Xinyi simply ignored whether these technologies were currently mature and just put on a "you're dead" face, coldly telling the young man:

"Idiot, still stubbornly holding on with such limited knowledge?!"

"You probably have no idea, do you—"

"All a Forensic Officer needs to do is take the blood-stained skin flakes from your body that glow blue, put them into a beaker, add digestive fluid to incubate, then extract them and pass them through a column for extraction and washing. They can use a purification column to repeatedly extract the large volume of digestive fluid, allowing the limited DNA in the digestive fluid to concentrate on the column membrane during this process."

"Finally, by adding a small volume of pure water for elution, high-quality, high-concentration DNA can be obtained."

To make his point more convincing, Lin Xinyi even explained the detailed procedure:

"At that time, the police will naturally be able to determine whose blood it is that's 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 was exceptionally pale.

He had indeed never heard of any scientific technology that could detect latent blood DNA, nor did he know if such technology truly existed.

However, hearing Lin Xinyi speak at length with such professional-sounding words…

Being uneducated, he could only believe it.

Thinking of this, the guy unconsciously broke out in a cold sweat.

He tensed his body nervously while instinctively stepping backward.

"You still want to run away?"

Lin Xinyi's brow furrowed slightly.

Miss Mouri Ran clenched her fists, making a crisp sound.

"I…"

The young man's eyes were filled with unwillingness.

But recalling the shattered wall at the stairwell, his face turned ashen as he stopped in his tracks:

"I confess."