National Forensic Doctor
Chapter 1029 - 962: Demarcation (Requesting Monthly Pass)

Chapter 1029: Chapter 962: Demarcation (Requesting Monthly Pass)

An Audi A6 with a Jing A license plate and a line of minibuses quietly entered the yard of the Changyang City Criminal Police Detachment.

Huang Qiangmin got out of his A6 first, followed by Jiang Yuan and others from the minibus.

Speaking of comfort on long-distance travels, the A6 doesn’t compare to the modified Coaster Lee. Not just because the seats are less comfortable, but in the Coaster, when you’re tired of sitting, you can stand up and walk around, twist your hips and waist - a feeling no amount of sedan stretching can match.

But, the A6 holds a special significance for Huang Qiangmin, especially one with a Jing license plate, much like wearing Louis Vuitton - greasy yet still fashionable.

Yu Wenshu greeted Huang Qiangmin, Jiang Yuan, and the others with a smile, then laughed, "The trace evidence that Jiang Yuan needed has all been finished overtime by our center. We did find something indeed. It’s quite the coincidence, hahaha..."

"Can we determine the source of the corpse?" Jiang Yuan got out of the car to stretch his limbs and was pleasantly surprised to hear this.

Yu Wenshu smiled and waved his hands, saying, "Not to that extent. Ah, but speaking of coincidences, I remembered something. I’m not sure if you guys still remember, our first case working together, the 326 kidnapping and murder case, the Tan Yong case, where the guy built an underground cellar to imprison people. The first breakthrough came from Jiang Yuan’s suggestion to use trace evidence method, and we found a body-hiding spot through it."

Yu Wenshu clapped his hands and put on a reminiscent face, saying, "I remember I said at the time, Jiang Yuan found a location where the body was hidden using trace evidence, which was quite reasonable!"

"That really is a coincidence!" Jiang Yuan and Huang Qiangmin were startled and laughed in agreement.

They generally remembered the case, the logic and evidence of the investigation were imprinted in their minds, but to recall in verbatim the actual conversation during a face-to-face meeting - faced with Yu Wenshu’s recollection, it was somewhat terrifying.

"That’s what you call a photographic memory." Huang Qiangmin gave a genuine compliment.

Jiang Yuan also sized up Yu Wenshu head to toe. Having to admit, this kind of skill in someone else’s hands felt quite unsettling.

"Wan Baoming never loses an argument with his wife." The deputy director of the Changyang City Criminal Science and Technology Center, Wan Baoming, had a very technical aura and spoke in a way that left one unsure whether he was making a complaint or not.

And he obviously knew Yu Wenshu’s soft spot. Chief Yu even showed a bit of pride as he waved his hand and said, "That’s nothing to boast about. I just have a good memory for things I’ve seen and conversations I’ve had, but if you ask me about the scene itself, I can’t remember that well. I don’t have a photographic memory."

"There’s actually a photographic memory? Like remembering events exactly as if they were photos?" Liu Wenkai joined the conversation, mainly to show his face and get familiar with the others.

Yu Wenshu nodded earnestly: "It’s not that rare... When I was studying, some people could glance at a chart in a book and redraw it on their notepads in no time. People like us just couldn’t do that; we had to read each word carefully and understand it to make sense of everything and be able to draw a relationship diagram."

"That’s why, back when we took exams, we had to compete with those students," Wan Baoming continued, with a tone of mock complaint to boost Yu Wenshu.

Yu Wenshu laughed heartily, "Nowadays in exams, we don’t have much of an advantage. At most, our liberal arts scores are a bit higher, but have you seen those science geniuses? They glance at a geometric figure and pop the answer right out. It’s as if... their brains just spit out the answers directly."

"These kinds of people don’t have much of an advantage when they argue with their wives," Huang Qiangmin laughed.

"The result is the same. Photographic memory, math geniuses..." Yu Wenshu’s face was full of world-weariness: "All end up sleeping on the couch!"

"Even if you win the argument, you still end up on the couch?" Liu Wenkai was somewhat inexperienced in this area.

Yu Wenshu nodded seriously: "You’ll understand later on. She doesn’t have to argue, just points her finger, making you figure out where you went wrong. Frankly speaking, a good memory can indeed help remember mistakes!"

Yu Wenshu was filled with emotion and then looked at Liu Wenkai, furrowing his brows, "Wenkai, I remember you’re also around 40, right? Still so inexperienced?"

Liu Wenkai, who had just been promoted to a deputy head position like Wu Junhao, helplessly touched his forehead and said, "Well, about that... I suppose I’m just rather good at sweet-talking..."

"How do you sweet-talk?" All the married men in the room turned their attention to Liu Wenkai.

Liu Wenkai: "Well, you know... I used to often visit brothels... No, I mean, crack down on prostitution, and I picked up some conversational techniques from that. Also, when I worked undercover, contacting informants and such required a bit of charming..."

"Right, I remember that. When Changyang City Public Security Detachment organized a cross-regional prostitution raid, they called you over. You were the first to catch a perp, right?" Yu Wenshu’s memory was triggered, and he quickly began to label Liu Wenkai.

Liu Wenkai quickly modestly replied, "Tied for first. Those dressed in drag don’t count."

Yu Wenshu’s memory was triggered a second time, and he said with discomfort, "Let’s talk about our case... Baoming, you tell the story."

As they spoke, they had already entered the office. Yu Wenshu sat down naturally, picked up his tea, and took a couple of gentle sips.

Wan Baoming was Changyang’s Criminal Science expert. He had made a name for himself 20 years ago, and though it couldn’t be said that he had fallen behind with the technological advancements over the years, he had not quite kept up either. He could understand the broad strokes and overview the big picture, so he could only serve as a leader within the Criminal Science Department, not as a technician anymore.

Wan Baoming cleared his throat, took out a report from his chest pocket, thought for a moment, and then smiled, "Perhaps because we tested many points for trace evidence and found various compounds, I’ll just tell you the conclusion directly. The fibers sampled from the body pieces and the woven bag found at the scene have the same fibrous structure; they are multi-layered bags made of polypropylene and flat filament woven with coated polypropylene. Both the warp density and weft density are relatively high, belonging to a better quality of woven bags."

Wan Baoming: "What’s particularly special is that we have confirmed the murderer used woven bags from three different manufacturers—one green and two blue..."

Wan Baoming: "Additionally, there are some textile fibers which are likely from the victim’s clothes worn while they were alive, including cashmere and cotton products—both natural fibers, which are relatively complex. Whether we can definitively identify the manufacturer remains uncertain."

The examination of trace evidence is quite complex, or rather, it constitutes an entire set of complex procedures.

First, there’s no machine where you can just insert trace evidence and get results—just like other forms of testing, such as DNA or toxicological analysis.

Secondly, when examining a piece of trace evidence, the examiner must first classify it, deciding whether it is metal, plastic, or something else like paint, rubber, glass, etc. This might involve observing it under a microscope, using an X-ray machine, or even dissolving a tiny amount in solvents. In short, precise categorization is required before further testing can be conducted.

For instance, having categorized it as a fiber, one can then analyze the characteristics of the fiber. They would examine its color, composition, cross-sectional morphology, polarized light properties, fluorescence, infrared spectrum, Raman spectrum, etc...

After completing these analyses, classification can proceed—first by determining if it’s a natural or synthetic fiber, and then identifying the specific type of natural or synthetic fiber.

If it’s a natural fiber, it could be cotton, linen, silk, wool, etc... If it’s a particular type of hemp, it could be ramie, jute, sisal, marijuana, flax, etc... If it’s a specific kind of marijuana, well, then we’re back to a course on marijuana to determine which variety it is...

For the police, merely identifying the type of fiber doesn’t mark the end of the investigation. They need to infer and confirm what the fiber was used for. If they ultimately want to use it to identify the source of the corpse, they must trace the journey from fiber to material, from material to manufacturer, and from manufacturer to consumer, step by step.

After going through this process, people would be running on fumes.

It’s only relatively simple if there are woven bags at the scene that can directly be used for comparison.

But to trace a piece of clothing back to the consumer is a much more challenging task.

Jiang Yuan listened to Wan Baoming’s briefing, then asked for several reports to read. After a while, he said, "In short, the fibers suspected to originate from clothing are hard to trace back to their sources... What about the woven bags, do you have any ideas?"

Wan Baoming took a sip of tea and said, "The types of fibers from the micro-evidence can all be matched with woven bags found at the scene. Currently, there are six different woven bags at the scene, originating from three different manufacturers. This is not normal. It at least indicates that the murderer didn’t buy these bags recently, but had them in stock."

"So you suspect that the murderer’s work or perhaps the primary crime scene involved using woven bags?" Jiang Yuan interpreted Wan Baoming’s words.

"It’s a possibility, at the moment..."

"But the scope is still quite broad. Have all the body parts been confirmed as belonging to one person?"

"Two of the pieces were too decomposed for DNA extraction, but the rest have been confirmed to be from the same person." Wan Baoming paused before adding, "I’ll go back and have someone try again."

The latter remark was purely out of respect for Jiang Yuan’s face. When you engage national-level experts, your level of expertise and attention to detail must also be at a national level, otherwise, if the killer is caught in the future and a mistake is found here, it would be highly embarrassing.

Jiang Yuan: "We can try again. It would also help to expand the search in the vicinity. If we can find the head, at least we could use skull reconstruction for the case, even though it’s time-consuming..."

Yu Wenshu responded: "We’re already expanding the search area, and the K9 unit is also providing support."

"In that case, there’s not much more we can do," Jiang Yuan said with a hint of difficulty, yet his tone and expression remained upbeat. He swiftly added, "How about this: I’ll establish a relatively accurate time of death, and we proceed in two steps."

"Okay."

"One, based on the time of death, we’ll look at nearby surveillance to see if there’s anything to uncover. It will be great if the suspect transported the body in an open-bed truck or tricycle."

Yu Wenshu chuckled: "You wouldn’t believe how common similar cases are."

Jiang Yuan smiled back with the little amount of EQ he had left, and continued, "Collect as much surveillance footage as possible. If there are any doubts, I can conduct further optimization here."

Yu Wenshu: "Alright!"

Jiang Yuan: "Second, based on the time of death, let’s scan for missing persons. I’ve seen the DNA reports; if the victim is female, we can widen the scope a bit, look across the province for missing females a week before death, and see if there’s a match."

"No problem." Yu Wenshu appreciated Jiang Yuan’s rare show of EQ and felt warmed by it. Although Jiang Yuan’s approach was simple, even typical for criminal investigators, it highlighted a critical point: the importance of determining an accurate time of death.

In thinking about the extensive investigations to follow, including the costs of personnel and case management, everything would pivot on this detail. Most forensic doctors wouldn’t dare to give a very specific time of death, and if they did, it would be too broad to be meaningful.

It was in Jiang Yuan’s company that Yu Wenshu could feel the fervor of his younger days, that intense feeling of being protected and cared for, inexplicably enveloping him.