Chapter 418

Xu Xu Taining arrived at the Criminal Police Detachment by bus, looking extremely plain. He didn't even need to park; he just walked slowly into the detachment wearing a pair of polished police trousers and a dusty jacket.

The new officer on guard duty at the gate only checked his ID before quickly saluting and letting him in.

In this day and age, one really shouldn't mess with a plain old man wearing a jacket.

In the detachment's conference room, Yu Yu Wenshu had set up a combat command center for Xu Xu Taining. A map and topographic map of Changyang City were hung on the wall, and a white porcelain cup with green tea was placed on the table. He wore a smile, prepared everything perfectly, and hid a small ulterior motive: If you can save a little from your fingertips, we might be able to have a prosperous year.

Xu Xu Taining returned a smile to Yu Yu Wenshu, picked up the green tea, looked at the map, and said: "If you want to put up a map, it would be best to change to a larger one."

"Uh... a larger scale map? This one is already..."

"I mean the scope of the map..." Xu Xu Taining drew a circle in the air with his hand and said: "This is a map of Changyang City."

Yu Yu Wenshu thought to himself, that's because we are the Changyang City Criminal Police Detachment.

Of course, he couldn't say that, so he continued to serve him carefully: "We considered that the killer's several crimes were all carried out around the scenic spots within Changyang City..."

"Your consideration makes sense; it is indeed possible that the crimes were carried out around scenic spots within Changyang City," Xu Xu Taining nodded, then added: "But it's also possible that they were carried out around scenic spots on the outskirts of Changyang City, or perhaps..."

Xu Xu Taining took a laser pointer out of his old jacket, shone a red beam, and walked along the map, saying: "It's also possible that they were carried out around the ring road or the ring expressway of Changyang City."

Yu Yu Wenshu felt completely numb. Changyang City is a provincial capital; the ring road must be 50 kilometers long, and if it expands further outward... If they were to conduct a screening, even if the Criminal Police Detachment's budget were ample, it couldn't withstand such spending...

The political commissar was even more terrified, fearing that Yu Yu Wenshu would just agree to it, so he quickly said: "The entire ring road is under surveillance. The entrances and exits to the elevated roads have had high-definition cameras for the past few years. If the killer took this route, he would be digging a pit for himself."

"What if he took a bus or a taxi?" Xu Xu Taining asked in return.

The political commissar was stunned. Indeed, the killer is just out to kill; he doesn't need to transport or dump bodies, nor does he need to dismember or bury them. He carries a nail gun with him, arrives at the chosen location—he doesn't even need to choose, just randomly find a place—gets off, climbs the mountain, kills, and goes home. He doesn't need to drive himself; public transportation makes it even easier to hide traces.

"If we draw such a large scope, the expenses will be too high. The bureau won't allow us to screen the entire city," Yu Yu Wenshu said cautiously.

"It's normal to be limited by conditions. The problem I encounter most often when doing screenings—the problem I encounter almost every time—is limited conditions and budget constraints..." Xu Xu Taining said naturally: "However, I proposed this scope because I hope you understand that it's impossible to cover every single detail. We must assume that the killer is also subject to some limitations. If we don't make such an assumption, our budget will have problems. But if the assumed scope is drawn too small, our screening might not be effective..."

Yu Yu Wenshu and the political commissar looked at each other, only then realizing that Xu Xu Taining was giving them a preemptive warning.

At the same time, both felt an even deeper sense of fear—Xu Xu Taining was giving them a preemptive warning!

How much money is this guy planning to spend?

"Let's change this map." Xu Xu Taining turned the laser pointer in the air again.

"Okay. Then how large a map do you want?" Yu Yu Wenshu's expectations had already been raised very high.

Xu Xu Taining shook his head at this moment and said: "After you called me yesterday, I studied this case. I believe that screening the crime scenes, or rather, screening the paths, methods, etc., that the killer used to enter the crime scenes, doesn't have much significance. The investment would be very large, but it's still possible to miss the culprit. It belongs to a mode that costs money but has poor results."

Yu Yu Wenshu recalled the scope Xu Xu Taining had just drawn and remained silent.

Indeed, the three cases occurred in three different directions in the suburbs of Changyang City, and all were in parks with relatively good scenery, hilly small mountains, where citizens go for leisure, some living nearby, and some coming from the city center. Considering that the ring road is not

far away, and even not too far from nearby towns,

screening the crime scenes and paths is indeed suspected of being thankless work.

Furthermore, the killer's three crimes were random, so the locations could also be random. Although human randomness is mostly pseudo-random, using a relatively simple analytical method—for example, drawing circles with the three crime locations as centers—the intersection of the three circles could be the killer's residence or work range. However, in real case analysis, who would dare to be so simple? The definition of this scope has too many premises, such as assuming road conditions are uniform, assuming the killer didn't change transportation, assuming the killer started from the same location each time, assuming the killer didn't encounter unexpected situations on the way...

If one only pursues a 50% homicide clearance rate like foreigners, then drawing circles like this isn't a big problem.

But since they had reached the point of inviting Xu Xu Taining, how could Yu Yu Wenshu dare to draw circles like that?

Yu Yu Wenshu looked at Xu Xu Taining vigilantly.

As the saying goes, a dog can't change its habit of eating excrement; Xu Xu Taining's way of spending money like water wasn't practiced in a day. It was something that criminal police teams at all levels in Shannan Province had pampered him into over time.

If he says it costs a lot of money, it might really cost a lot of money, but if you think he will save money, then you are just dreaming.

"Surveillance video can be checked, but I don't think we should count on it too much. In the wilderness, as long as the killer wears a hat, carries an umbrella, or wears a hoodie, we'll be wasting our efforts." Xu Xu Taining cut off another path.

Yu Yu Wenshu nodded solemnly.

"For this case, I think it ultimately comes down to the weapon. Because the most special thing about this case is the weapon. A modified nail gun. Where did the nail gun come from? Where was it modified? Who modified it? I think as long as we solve one of these three problems, the case can be solved." Xu Xu Taining counted on his fingers, breaking the case into pieces, yet making it clear and understandable.

Hope couldn't help but appear on Yu Yu Wenshu's face.

Xu Xu Taining's analysis was indeed much more meaningful than looking for evidence at the crime scenes.

Xu Xu Taining took a sip of tea and said slowly: "There are quite a few people capable of modifying a nail gun, but actually not that many. My estimate is, just in Changyang City and the surrounding areas, a few tens of thousands..."

Yu Yu Wenshu was stunned: "A few tens of thousands?"

Xu Xu Taining: "Those engaged in the machinery industry, electricians, all are possible..."

"Wait," the political commissar said: "Even if we show up at their door, how do we prove he modified a nail gun?"

"The time of the three crimes—all three occurred in the morning, two on workdays, one on a day off. The distances between the three are also very far; his alibi must be incomplete. Screen the list, then see if there are ways to screen further." Xu Xu Taining answered quickly.

Yu Yu Wenshu knew that Xu Xu Taining's work mode was like this: when in doubt, screen the list first. If the number of people screened is small, conduct specific inquiries, use a lie detector, or conduct secret investigations. If there are too many people, change the screening direction, conduct cross-comparisons, and after narrowing down the list, return to the first step.

Come to think of it, Xu Xu Taining's way of solving cases is also cumbersome, just different from Jiang Yuan's cumbersome method, and it just costs more money.

Yu Yu Wenshu missed Jiang Yuan for a moment, then took a deep breath: "Let's do it. Do as you say."

This case would not allow him to hesitate or waste time anymore.

Afternoon.

While Xu Xu Taining was still in the preparation period, a reporter from the "Changyang Evening News" arrived at the Criminal Police Detachment.

The reporter was called by the bureau chief. Her attitude was very good, very professional, and she looked very serious. She asked many questions, some of which were clearly prepared with the help of professionals.

Yu Yu Wenshu answered obediently. He was now a detachment leader in the provincial capital, so the person who came was a reporter. If he were still

a brigade leader, what might have come would be a fruit platter. The meaning is about the same: if the case is solved, you eat the fruit, it's sweet; the reporter writes a report for you. If the case can't be solved, there might not be a report, but a report will definitely be sent up.

Yu Yu Wenshu not only secretly rejoiced that he had invited Xu Xu Taining, but this way, even if he died, he would die without regrets...

At the same time, Jiang Yuan was also racing against time to look at the nails.

The killer in this case had already killed three people. Although the interval between the two times was uncertain, you couldn't expect a serial killer to follow a schedule. Especially this kind of random killing without conflict of interest, which shows that he himself does not follow social order,

and does not identify with existing social moral norms.

Therefore, the killer could start killing a fourth person at any time. Completing the comparison of the long nails as soon as possible was the best breakthrough Jiang Yuan could see at the moment.

After being influenced by, participating in, and solving so many cases, Jiang Yuan had gradually formed his own criminal investigation cognition.

In his view, the killer in this case must have gone through a long period of planning, envisioning, and designing before committing the crime. This kind of serial killer is fundamentally different from an ordinary person committing murder.

When an ordinary person commits murder, on one hand, they are limited by interests, so there are ties and handles. On the other hand, ordinary people usually only start planning and implementing murder under the condition of extreme loss of interest. Moreover, planning doesn't mean it will be implemented; usually, it requires continuous loss of interest or the appearance of a trigger point before they implement it.

As a result, when ordinary people commit murder, they have both interest ties and time constraints, not to mention emotional impulses. All of these make them restricted in every way when it comes to killing, making it difficult to reach the peak state of intelligence and physical strength.

Serial killers are different. The core of a serial killer is the antisocial factor; in psychological terms, it is the lack of empathy. Ordinary people, when they are very young, such as in the toddler stage of two or three years old, will cruelly and unhesitatingly kill ants, insects, and other weak creatures, but as they grow older, they do this less and less. This is the germination of empathy and the result of social education.

Serial killers won't be like this. Because of various reasons, they have lost their empathy, so their attitude toward humans is similar to a toddler's attitude toward ants. Of course, their intelligence is normal, so they can also understand the requirements of social morality and where the boundaries of the law are.

In order to avoid punishment while satisfying their inner needs, serial killers often plan to kill from a very young age, holding it in until they are adults to execute it. They have already belonged to the self-trained category.

Facing such criminals, using ordinary means to deal with them is definitely not going to work.

At this time, it belongs to what the police have thought of, and they have very likely already thought of it—only referring to high-end serial killers; those weak ones were already screened out during their first crime.

Jiang Yuan saw the long nails and could even imagine the killer's smugness.

The killer could have used steel balls, but he still used ordinary long nails that are harder to track, and specifically modified a nail gun for this purpose. This shows that he is very clear that the "bullets" fired from the nail gun are his biggest flaw. He can take away the shell casings, take away the nail gun, and pay attention to footprints and fingerprints, but he cannot go to the scene to dig out the bullets or the long nails; that might leave behind even greater hidden dangers.

However, based on Jiang Yuan's work over the past two days, he felt that the killer's time in the world was getting shorter and shorter.

If Jiang Yuan was still worried about not finding suitable long nails in the initial stage, after these few days, Jiang Yuan's confidence had already risen.

In Jiang Yuan's view, comparing long nails and comparing fingerprints actually have commonalities.

The pursuit of fingerprint comparison is actually not about being identical. Mark feature points, sort according to the number and similarity of feature points, and then look for the closest one among the candidate fingerprints, and eliminate fingerprints with obvious differences...

Comparing long nails is actually also about feature points.

It's just choosing those positions that are easy to leave traces on and constantly comparing them.

Now, Jiang Yuan can directly eliminate more than half of the nails he gets in his hands. Many reasons for elimination don't even

need to be looked at with the eyes; just by weighing them in his hand, he can cast them aside.

This also greatly advanced his progress.

Who would have thought that Level 6 tool mark inspection would actually have room for improvement formed through self-training.