Chapter 1362: Cross-Reference

Blood handprints are almost the favorite fingerprint type for the criminal science department.

Compared to ordinary latent prints, blood handprints are like the suspect actively applying plaster—almost all the finest ridge details on the print can be revealed, and they can even look better than those made with plaster.

But after wiping, it's different.

When wiping fingerprints while the bloodstains on the hands are still wet, the ridges become saturated with blood, so there's no basis left for fingerprint comparison.

However, after carefully examining the scene photos of "Cui Ling 211," Jiang Yuan is certain that after the killer wiped his hands on the curtain and towel, some fingerprint fragments still remained at the edges.

That is, when the fingers were about to dry but not completely dry, some partial fingerprints were still left on them.

Through a simple crime scene reconstruction, it can be seen that when the killer used the curtain to wipe his hands, he had already killed two people and was preparing to go upstairs.

Because he used excessive force initially, the killer stabbed Zhang Guoyi and his wife more than ten times, soaking his gloves with blood, forcing him to remove the slippery gloves, wipe his hands again, and then tie the knife with a towel—these steps can be confirmed based on the bloodstain patterns at the scene.

If using conventional fingerprint identification methods, whether the prints are collected from the curtain or the towel, they are basically useless.

The remnants are too severe—possibly fewer than three to five characteristic points can be marked—and when entered into software for comparison, the resulting candidate prints would be astronomical in number.

Using a high-resolution spectral imaging device would help a bit; the few fingerprints at the curtain's edge all yielded four or more characteristic points. The fingerprint quality on the towel is much worse, yielding only about three to four characteristic points at most.

Jiang Yuan therefore focused on the curtain.

Following the principle that seven points are usable and eight offer a chance, four or five points are still too distant, so at this point, image enhancement techniques must be used to try to add one or two more characteristic points to the base of five.

This process proceeded very quickly, to the extent that the two fingerprint experts, Liu Changhe and Lin An, also quickly felt dizzy and disoriented.

Image enhancement itself is a highly counterintuitive operation; even basic grayscale adjustment already determines the image numerically. To non-professionals, just watching Jiang Yuan's procedure would seem confusing.

Liu Changhe and Lin An together have LV0.5 image analysis capability, but watching Jiang Yuan's operation, they only feel it's hallucinatory and exciting.

This is exactly the kind of Jiang Yuan they want!

If they were ordinary fingerprint experts, why would they have come to An Wan? They could handle it themselves.

Jiang Yuan was busy at the computer for a while, then stood up and pulled the evidence curtain to perform image collection.

Liu Changhe and Lin An hurried forward to help pull the cloth.

Amid the busyness, Criminal Investigation Brigade Chief Liu Zhuangshi walked in.

"Oh, you're retaking fingerprints?" Liu Zhuangshi looked at them working hard, and his inner anxiety seemed to be soothed somewhat.

Although I've been struggling everywhere for funds, the hard-won budget hasn't been wasted—it's being used by a genius detective like Jiang Yuan. Thinking this way, I feel especially reassured.

"There's a fingerprint here with some hope." Jiang Yuan gave Liu Zhuangshi a brief explanation—no need to over-explain.

Liu Zhuangshi nodded repeatedly and said happily: "Great! The Cui Ling 211 case is highly likely to be a repeat offender's crime spree. If we can find fingerprints, the match probability should be quite high."

He's just saying what sounds good. To Jiang Yuan and the others, the biggest worry about this case is whether the killer's fingerprints are in the database.

But as Liu Zhuangshi analyzed, since the killer in the Cui Ling 211 case isn't acting out of revenge, the probability of it being a repeat offender's crime spree is very high. This is because the killer's killing process was bold yet meticulous—he murdered the upstairs couple, then deliberately wiped his hands clean, rewrapped his hands and knife with a towel, and without hesitation went upstairs to kill the child and grandmother… Someone who hasn't trained in prison would find it hard to master this entirely.

Jiang Yuan only slightly nodded and said: "We're not yet sure how many characteristic points we can make out. If we could get seven, that would be excellent..."

"Just like in previous cases, you list a suspect list, and I'll have people take their fingerprints again..." Liu Zhuangshi had already begun relying on procedure.

Jiang Yuan hummed and said: "I plan to first screen with footprints. That way, even if only six characteristic points come out, we can still generate a usable list."

Not only Liu Zhuangshi, but Liu Changhe and Lin An also looked over and, in unison, said: "Can footprints also be used?"

"This case has bloody footprints all over the ground—it would be a waste not to use footprints." Jiang Yuan said while speaking, and again marked fingerprints.

Liu Zhuangshi asked: "To what extent can footprints determine things?"

Jiang Yuan didn't even lift his head and said: "Based on the time of the crime, the killer should be a male around 23 years old, about 1.75 meters tall, weighing 150 jin, wearing size 42 shoes, slightly oversized by half a size, with an out-toed gait."

"Good, good..." Liu Zhuangshi nodded repeatedly, his expression unconsciously relaxing, even entertaining the thought that this case might not be so difficult after all.

Of course, this thought only flashed for a moment—the Cui Ling 211 case became a major case precisely because multiple investigations failed to break through. Just looking at old photos and old evidence, claiming to solve this case—Liu Zhuangshi simply doesn't have the guts for that.

The members of Jiang Yuan's cold case task force, however, are in surprisingly high spirits. Hearing the news here, they've already actively signed up in the small group:

【Should we implement a rotation system? Those who've already gone shouldn't suffer too much—let those who haven't gone take their turn.】

【Volunteer to go on a business trip to impoverished border regions.】

【You're thinking too well—impoverished border regions are where you're most likely to succeed!】

In the lighthearted chat, Wang Chuanxing initiated a lottery draw, initially ordering eight people; if the later team formation requires more members, another draw will be held.

In a warm and friendly atmosphere, Jiang Yuan completed the final characteristic point marking.

Six characteristic points—computer auto-search yields at least ten thousand matching fingerprints. Under normal circumstances, screening would be meaningless, because behind these ten thousand prints are even more secondary prints with slightly lower similarity.

But when the footprint analysis results are cross-referenced, the number of matching fingerprints instantly drops to dozens.

This number is neither many nor few, but it's already operable.

Liu Changhe and Lin An exchanged glances, their eyes somewhat excited. For Jiang Yuan, this case is just routine; for the An Wan Municipal Bureau, it's a major case; for them, it can be said to be a breakthrough in their careers.

"48 groups—if each group is still four people, I'll need to request some reinforcements." Liu Zhuangshi said what he said, his expression still relaxed. Sending out 200 people for such a case is nothing.

Of course, calculating precisely is also terrifying: the daily subsidy for 200 people is 36,000 yuan; going out for just three to five days would be a small 200,000 yuan in expenses. Round-trip fuel or airfare costs are also significant—even if all are local police, the travel expenses for 200 people going out for 200 days would still count as saving 2 million yuan.

At this critical moment, as an insider in the system, Liu Changhe immediately said: "If there are financial difficulties, I can help apply for subsidies from the central ministries..."

Lin An also said: "If there are any inspection-related items, they can be sent directly to our lab, where they charge the minimum fee—should also save a bit."

Li Zemin, who has long been on the front lines and knows how to save money, said: "We could also consider first marking these 48 people, prohibiting overseas travel, then checking their prior records. If we process them in two batches, personnel burden and travel expenses would be much lower—perhaps a province or a city might even have several suspects. They don't know we're investigating the Cui Ling 211 case, so timing shouldn't matter."

Jiang Yuan cleared his throat, handed a cigarette to Li Zemin, looked at Liu Zhuangshi, and said: "What do you think?"

After all, the case is being handled by the An Wan Municipal Bureau—they're independent bigwigs; we can't demand too much.

Liu Zhuangshi then gritted his teeth: "Doing it all at once is safest. We finally have a bit of opportunity……As for people, we can still second some youngsters over. Money……I'll go talk to the bureau chief!"