Chapter 418

Xu Taining came to the Criminal Police Detachment by bus, looking extremely simple. 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 police officer on guard at the gate only checked his ID before quickly saluting and letting him in.

In this day and age, you really don't dare to mess with a simple old man wearing a jacket.

Yu Wenshu opened a combat command room for Xu Taining in the detachment's conference room, hung a map and topographic map of Changyang City on the wall, placed a white porcelain cup on the table with green tea inside, and wore a smile on his face, preparing everything perfectly while hiding a small thought: If you can save a little from your fingertips, we might be able to have a prosperous year.

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

"Uh... a large-scale map? This one is already..."

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

Yu Wenshu thought to himself, because we are the Changyang Municipal Criminal Police Detachment.

Of course, he couldn't say that, so he still served him carefully and said: "We are considering that the killer's several crimes were all carried out around the tourist attractions within Changyang City..."

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

Xu Taining took out a laser pointer from his old jacket, shone a red light, 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 Wenshu felt completely numb. Changyang City is a provincial capital; the ring road must be 50 kilometers long. If they expand further out... if they conduct an investigation, even if the Criminal Police Detachment's budget is abundant, it can't withstand such spending...

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

"Maybe they took a bus or a taxi?" Xu Taining asked in return.

The political commissar was stunned. Indeed, the killer is just out to kill people; he doesn't need to transport or dump bodies, nor does he need to dismember or bury them. He carries a nail gun, goes to a selected place—or doesn't even need to select, just randomly finds a place—gets off, goes hiking, goes up the mountain to kill, and goes home after killing. He doesn't need to drive himself; public transportation is actually easier to hide traces.

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

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

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

At the same time, the two felt a deeper sense of fear—Xu Taining was giving them a heads-up!

How much money is this guy planning to spend?

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

"Okay. Then how big of a map do you want?" Yu Wenshu's expectation value had already been raised very high.

Xu Taining shook his head at this time and said: "After you called me yesterday, I studied this case. I think investigating the crime scene, or rather, investigating the path and method the killer used to enter the crime scene, etc., doesn't have much significance. The investment would be very large, but it's still possible to miss the target. It belongs to a mode that spends money but has poor results."

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

Indeed, the three cases occurred in three directions in the suburbs of Changyang City, and they were all parks with relatively good scenery and small hills. There were citizens going for leisure, people living nearby, and people coming from the city. Considering that the ring road is not far

away, and even not far from nearby towns,

investigating the crime scenes and paths really has the suspicion of being thankless.

Furthermore, the killer's three crimes were random, so the locations could also be random. Although most human randomness is pseudo-random, using a relatively simple analysis method—for example, drawing circles with the three crime locations as the center—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 delineation of this range has too many premises. For example, assuming road conditions are uniform, assuming the killer didn't change transportation, assuming the killer started from the same place each time, assuming the killer didn't encounter accidents on the way...

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

But since it reached the level of inviting Xu Taining, how could Yu Wenshu dare to draw circles like that.

Yu Wenshu looked at Xu Taining vigilantly.

As the saying goes, a dog can't change its habit of eating feces. Xu Taining's way of spending money like water wasn't practiced in a day. It was pampered step by step by criminal police teams at all levels in Shannan Province.

If he says it costs a lot, it might really cost a lot, but if you say he will save money, that's just wishful thinking.

"As for surveillance video, we can check it, 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 all be working in vain." Xu Taining cut off another path.

Yu Wenshu nodded solemnly.

"For this case, I think it ultimately has to come 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 Taining counted on his fingers, breaking the case into pieces, yet clear and understandable.

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

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

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 its surroundings, a few tens of thousands of people..."

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

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

"Wait." The political commissar said: "Even if we show up at their door, how do we prove that they 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 three distances are also very far apart. His alibi must be incomplete. Screen out the list, and then see if there are further ways to filter." Xu Taining answered quickly.

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

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

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

This case doesn't allow him to hesitate or waste time anymore.

Afternoon.

While Xu Taining was still in the preparation period, a reporter from the "Changyang Evening News" came to 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 looked like they were prepared by professionals.

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

a brigade chief, what might have come would be a fruit platter. The meaning is about the same: if the case is solved, eat fruit, sweet and silky, and the reporter will write a report for you. If the case can't be solved, there might not be a report, but a report will definitely be submitted.

Yu Wenshu not only secretly rejoiced that he had invited 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 has already killed three people. Although the interval between the two times is uncertain, you can'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 the fourth person at any time. Completing the comparison of the long nails as soon as possible is the best breakthrough Jiang Yuan sees at the moment.

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

In his view, the killer in this case must have gone through a long period of planning, conception, and design before committing the crime. This kind of serial killer is fundamentally different from ordinary people who kill.

When ordinary people kill, on one hand, they are limited by interest-related factors, so they have ties and handles. On the other hand, ordinary people usually start planning and implementing murder only when their interests are greatly damaged. Moreover, planning doesn't mean it will be implemented; usually, it requires continuous damage to interests or the appearance of a trigger point before they implement it.

As a result, when ordinary people kill, they have both interest entanglements 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 of intelligence and physical strength.

Serial killers are different. The core of a serial killer is anti-social factors. In psychological terms, it's a lack of empathy. Ordinary people, when they are very young, such as in the toddler state 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 escape punishment while satisfying their inner needs, serial killers often plan to kill from a very young age and execute it after reaching adulthood. They have already belonged to self-trained individuals.

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 thought of, and they are very likely to have already thought of it—specifically high-end serial killers. Those weak types were already screened out during the first crime.

Seeing the long nails, Jiang Yuan could even imagine the killer's pride.

The killer could have used steel balls, but he still used ordinary long nails that are harder to track, and specifically modified the 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 pick out the bullets or long nails, as that might leave behind greater hidden dangers.

However, based on Jiang Yuan's work over the past two days, he feels that the killer's time in existence is 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 has already risen.

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

The comparison of fingerprints actually doesn't pursue being exactly the same either. Mark the feature points, sort according to the number and similarity of the 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 positions that are easy to leave traces and constantly comparing them.

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

need to be seen with the eyes; just by weighing the weight in his hand, he can toss them aside.

This also greatly advanced his progress.

Who would have thought that Lv6 tool mark inspection would actually have room for improvement formed by self-training.