Chapter 1223: Rain-Slicked Night

A rainy night is a natural bug in modern forensic science.

The Locard's Exchange Principle, so often mentioned by people—that whenever two objects come into contact, a transfer of material must occur, meaning something will be taken away and something will be left behind—is the foundation of criminal investigation.

The vast majority of forensic techniques follow Locard's Exchange Principle. Under this principle, the world seems as beautiful as elementary mathematics, as if everything is self-consistent and solvable.

Time is a heavy blow to Locard's Exchange Principle; as time passes, much evidence gradually disappears and then dissipates.

But resisting time is, in itself, the part of humanity that is both most familiar and most resigned...

A rainy night is different.

It can wash away evidence and alter the crime scene on the very day the crime occurs.

Rain falling from the sky onto a corpse, the ground, or even the suspect's body can potentially wash away evidence. And the rainwater it exchanges and transfers back obviously cannot be held criminally liable.

There is a reason why many famous major cases and cold cases occur on rainy nights.

Of course, a rainy night has its own disadvantages, but no matter how you look at it, once a homicide occurs on a rainy night, the difficulty is at least +1.5 or higher.

Some ordinary, unremarkable cases that might have originally been small cases with a difficulty of around 0.5, with the added blessing of a rainy night, might directly become a difficulty of 2.0, enough to leave police officers below the level of backbone staff helpless.

In the famous Rainy Night Butcher case, the killer, a taxi driver, murdered four women in succession and earned his name because most of his crimes were committed on rainy nights.

This case had a huge impact and could be said to be the most famous serial murder case in the Hong Kong area. The number of police mobilized was countless. Not to mention the various events during the case, just looking at it from the perspective of hindsight, the killer was neither professional nor smart. Because he was caught only because he took photos of the corpses and organs to a photo studio to be developed.

You don't even need to be very professional or smart; if the killer had read a single detective novel, he wouldn't have done such a stupid thing.

Yet, such a stupid person, with the blessing of a rainy night, actually evaded the forward-looking investigation of the supposedly professional Hong Kong police force.

However, no one mocks the Hong Kong police either. Because the even more famous Scotland Yard, the FBI, or the Tokyo Metropolitan Police Department's First Investigation Division all have similar embarrassing stories.

Clearly, for Liu Jinghui, who fancies himself the Morse of Shannan, a rainy night homicide is a point that truly stimulates him.

"Murder, body disposal, uterus excised—how is the killer's technique?" Liu Jinghui didn't look closely at the photos, but let his thoughts wander, asking Jiang Yuan whatever came to mind.

Jiang Yuan closed his eyes to recall for a moment and said, "The incisions are forceful, the cuts are clean. The killer is highly likely to be male and robust. Just regarding the operation of excising the uterus, it wasn't done according to anatomical structure; it was basically pure brute force. The order of excision should have started from the abdomen, and there was no process of rummaging, which indicates he knew the location of the uterus. Can this be considered skilled technique?"

"If the technique is skilled, does that mean it wasn't the first murder?" Liu Jinghui asked this question, then looked at Cui Qishan and the others nearby, saying, "I see you had similar guesses in your previous investigations?"

"Yes, we also rummaged through some previous cold cases, especially cases that occurred on rainy days, or cases involving the excision of a uterus, but we didn't find any cases suitable for serial linkage." Cui Qishan answered quickly.

Serial linkage is the secret to solving cases, especially after a special task force is established and manpower is abundant; looking for old cases is a common occurrence.

Liu Jinghui nodded slowly: "What about cases outside the capital?"

"None. Excising organs is a very heinous act, and with the element of a rainy night, if there were similar cases, we wouldn't even need to search; just asking around would reveal them." This time it was Xiao Si who answered. He pointed outside and said, "The flow of people in the capital is complex; it's very likely that an outsider committed the crime while passing through. The key is, the victim was a local of the capital, and both her schooling and work were in the capital. How was she selected as the victim?"

Liu Jinghui said, "Excising reproductive organs—this action is often very symbolic. The killer choosing this victim probably wasn't because of her identity or interpersonal relationships. Of course, this is also a guess... the previous investigation..."

"The victim had an aunt who participated in an illegal church, but it didn't reach the level of murder; at most, it was just swindling money and sex... As for other aspects, if the killer chose randomly, this direction was also investigated, but there were no results..."

"Let's reorganize the evidence." Jiang Yuan didn't let Liu Jinghui continue asking.

They themselves didn't have a corresponding understanding of this case, and just asking questions was too inefficient for obtaining information.

With Jiang Yuan's words, everyone in the room began reading the case files according to their usual directions.

Wang Chuanxing continued to attend to Jiang Yuan alone, showing him various photos of decomposed corpses and various traces from the scene.

There were many of the former, but very few of the latter, and most were peripheral traces that weren't necessarily left by the killer or the victim.

While Jiang Yuan was looking at the photos of the traces, Cui Qishan said, "It often rains heavily in the capital. The night before the corpse was discovered, the rain was very heavy, and there was wind. The area where the corpse was located is prone to flooding, so even if there were footprints or anything, they might not have remained."

"You still have the clothes from the corpse, right?" Jiang Yuan pointed at the screen at this moment.

"We do, but most of them have also corroded. I remember they should be cotton textiles or something." After Cui Qishan finished speaking, he looked at Jiang Yuan full of hope and asked, "Can you use forensic botany?"

For the criminal police, Jiang Yuan's forensic botany is a bit like an ultimate move; even if it can't defeat the enemy in one blow, at least it can scrape off some health.

Jiang Yuan was amused by Cui Qishan's tone and said, "We can collect some spores and pollen for backup. If we really want to find a pollen map, we'd have to make a big fuss. You don't have a complete plant map, right?"

"You are right." Cui Qishan hurriedly admitted. Since Jiang Yuan had already said "make a big fuss," if he dared to follow up, he was afraid he would be the one the bureau would make a big fuss over.

"Then let's stop here for now. I'll go take a look at the corpse. As for the others, Director Liu, could you arrange it?" Jiang Yuan directly delegated the task to Liu Jinghui.

Liu Jinghui also agreed without hesitation, and then skillfully began to arrange for different people to investigate everything one by one, from surveillance videos to police reports, transcripts, and so on.

Jiang Yuan's cold case task force has done too many similar cold cases. Don't look at how much work the previous task force did; if you want to restart a task force, the investigations that can be done must be done. Otherwise, being suspicious and paranoid at that time will only waste effort. Of course, this is also a resource only Jiang Yuan's cold case task force has; ordinary guest forces can't afford to play this game.

Jiang Yuan went to the forensic building to see the corpse himself.

The two-year-old corpse, because the case wasn't solved, had been kept in an ice coffin the whole time. Until yesterday, it was frozen stiff.

This method can maintain the original appearance of the corpse to the greatest extent, similar to the "zombie meat" often talked about on the market. Think about how the remains of chickens, ducks, and pigs can be preserved for twenty or thirty years; it's not surprising that human remains can be preserved for more than two years.

Unfortunately, when the corpse was discovered, it was already mildly decomposed. After being frozen and thawed again, tissues like muscles gradually turned into stinking meat as they thawed.

Jiang Yuan had long been prepared. After fully protecting himself, he started the second autopsy without a word.

Zhan Kan arranged for people to start boiling hot water.

There is very little that can be done in a second autopsy; taking samples from where they can still be taken is about enough.

After this step was completed, Jiang Yuan had people throw the remaining corpse parts into the hot water to start degreasing the bones.

Finally, what was laid out on the autopsy table turned into gray-white bones, piece by piece.

Jiang Yuan scanned them from top to bottom.

"Is the victim 38 years old?" Jiang Yuan picked up a rib and suddenly asked.

"The case file says 38 years old." Wang Chuanxing hurriedly answered.

Jiang Yuan shook his head: "This corpse is only about 33 years old."

(End of chapter)