Chapter 9: Anping Electronics Factory

In recent years, the role of crime scene investigation (CSI) has become increasingly significant in the handling of various criminal cases.

More than a decade ago, it was a part-time job where any criminal police officer could step in and show off a few tricks, but it has since developed into a specialized departmental category.

This is especially true for the criminal investigation detachments of municipal bureaus, most of which have established professional CSI teams. In many cases, the CSI team and the trace evidence examination team share the same personnel under two different titles.

The Haizhou Municipal Criminal Investigation Detachment is one such case; the four members led by Liu Guodong handle both the on-site investigation and the subsequent evidence examination.

Of course, there are some formidable criminal investigation detachments that have over a dozen people for CSI and another dozen for trace evidence, but such staffing is generally reserved for provincial-level detachments at a minimum.

As a common form of information collected at crime scenes, footprint analysis has gradually developed into a specialized discipline.

However, whether at the Public Security University or in frontline criminal investigation detachments, there is an extreme shortage of talent in this field.

There are many reasons for this: on one hand, the teaching is not very systematic; on the other, some techniques are kept as closely guarded secrets; and finally, there is limited room for professional advancement.

Even if someone is truly willing to teach, there isn't necessarily anyone willing to learn.

Compared to fingerprint identification, footprint analysis is relatively lagging behind.

Therefore, the fact that Lu Chuan acquired the footprint analysis skill through the system is quite rare, even if it is only at the primary level.

However, even at the primary level, while it only means there are some things Lu Chuan has yet to master, it does not mean the skill rewarded by the system could be wrong.

There are many nuances to footprint analysis, starting with the measurements.

First is the determination of the "fringe" (the blurred edge). In a footprint, the center of gravity is concentrated in the ball of the foot.

However, because of the human arch, the middle part of a footprint is normally the lightest, while the ball and heel are the heaviest.

Taking the center of the ball of the foot as the focal point, the further outward one goes, the lighter the impression becomes, forming a blurred edge at the periphery.

For shoes of the same size, the size of this blurred edge indicates the weight of the owner.

The heavier the weight, the smaller the blurred edge.

By combining this with the length of the footprint, one can calculate the height and weight of the owner.

But in this case, the footprints left by the suspect had irregular blurred edges, fluctuating in size.

Although the difference was very subtle, it was still measurable.

This situation was most likely caused by the suspect wearing shoes that did not match their actual size.

At the same time, the blurred edges on the left and right sides of the ball of the foot also differed.

This meant that the suspect's shoes were not only longer than their actual size but also wider.

Combining this with the stride length and the weight calculated from the depth of the footprints under the conditions at the time, Lu Chuan determined that the owner of the footprints was female.

She had simply been wearing a man's pair of shoes, and a size too large at that.

No wonder they couldn't find the suspect; they had gotten the gender wrong—how could they possibly catch the person?!

Repeating the calculations to ensure his judgment was correct, Lu Chuan continued to infer the suspect's physical characteristics based on the footprint data.

"The inner edge of the footprint is slightly heavier, the outer edge slightly lighter... the person is knock-kneed (X-legged)."

"Excluding the influence of the blurred edges, the person's foot length should be 24.2 centimeters... height is around 1.69 meters, weight is around 61 kilograms..."

An hour later, the suspect's characteristics had been detailed.

Female, 1.69 meters tall, 61 kilograms, aged between 32 and 37, knock-kneed.

*Ding.*

"Basic task completed. The host has used footprints to analyze the physical characteristics of the robbery and assault suspect."

The moment Lu Chuan finished his calculations, the system's notification sound for completing the basic task appeared.

Next, Lu Chuan opened another stack of documents containing all the surveillance footage from near the crime scene at the time.

During the time of the robbery, thirty-two people had been captured on camera.

Of course, the suspect might not have passed by the cameras that captured the images, so this was merely a screening resource.

Lu Chuan opened the files and compared the portrait photos one by one.

Within a few minutes, Lu Chuan's gaze locked onto a woman named Zhang Yan!

"Heh, it's you!"

Taking the woman's photo, Lu Chuan locked the CSI storage room door and headed straight out of the criminal investigation detachment.

"Old Yang, are you at the station?"

Unlike Lu Chuan, who was assigned to the criminal investigation detachment, Yang Lin had been assigned to a local police station after graduation and became a beat cop.

As it happened, the area where Zhang Yan lived was within the precinct Yang Lin was responsible for.

Guanghua Street Police Station.

Yang Lin poured tea for Lu Chuan and took the file on Zhang Yan: "This person lives in low-rent housing. Let me check the records."

Given their relationship, there was no need for formalities. Lu Chuan stated his purpose directly: "This Zhang Yan is a suspect in a robbery and assault case from last year. See if you can collect her footprints; if they match, this cold case will be solved."

"No problem. Sit for a moment, I'll be right back."

Although the work at a local police station is complex, it is relatively relaxed.

Generally, the cases handled by a local station are mostly neighborhood disputes or petty theft.

Once a major criminal case (the "eight categories") occurs, it must be handed over directly; the local station usually only assists with screening work.

Of course, this doesn't mean a local station cannot investigate criminal cases; if a case handed over remains unsolved for a long time, the local station can apply to take it back.

Though, that would never happen for a homicide; no local station would go out of their way to request a murder case.

Like Lu Chuan, Yang Lin was professionally trained, and most of the work at the police station was relatively simple for him.

In less than two minutes, Yang Lin returned with a stack of materials and handed them to Lu Chuan: "This Zhang Yan works at the Anping Electronics Factory. She is a single mother raising a daughter and also cares for a paralyzed mother at home. She is one of our registered aid recipients."

An aid recipient?

Lu Chuan hadn't expected Zhang Yan's family background to be so impoverished.

"I've already contacted the electronics factory. Zhang Yan is still at work. Do you want to go now or wait until she gets off?"

After roughly scanning the documents, Lu Chuan thought for a moment: "Now. Let's go straight to the electronics factory."

Twenty minutes later, Anping Electronics Factory.

The workshop supervisor led Lu Chuan and his partner to the floor: "Officers, that's Zhang Yan, the one standing by the workstation wearing the blue uniform."

"Let's collect the footprints first."

This was simple. Lu Chuan had brought specialized footprint collection paper; one only needed to stand on it briefly to complete the collection.

As Zhang Yan stood on the paper, Lu Chuan carefully observed her expression. It was clear that she was nervous; her fingers were even trembling slightly, and her face was pale.

Sighing inwardly, Lu Chuan picked up the collected footprint and compared it directly on-site with the one found at the robbery scene.

Footprints, like fingerprints, are unique to every individual.

If the two footprints matched, it would confirm that Zhang Yan was the perpetrator.

"Officer... sir... no need to look... that person is me..."

Just as Lu Chuan was making the comparison, Zhang Yan, standing behind him, confessed in a trembling voice.

Criminal Investigation Detachment.

Qin Yong stared blankly at Liu Guodong, who was reporting to him: "Say that again?"

Liu Guodong was also stunned: "Lu Chuan just called. He said he and the beat cop at the Guanghua Street Police Station caught the perpetrator of last year's robbery and assault case."