civil forensic

Chapter 1342 Cross
Bloody handprints are almost the most favored fingerprint type among criminal investigators.

Compared to ordinary latent fingerprints, bloody fingerprints are like the suspect deliberately applying clay, which can reveal almost all the finest lines of the fingerprint, and can even be more beautiful than clay.

But it's different after you wipe it.

If you wipe your fingerprints while the blood on your hands is still wet, the lines of the fingerprints will be completely soaked with blood, making fingerprint comparison impossible.

However, after carefully examining the crime scene photos of "Cuiling 211", Jiang Yuan was certain that after the murderer wiped his hands on the curtains and towels, some fingerprint fragments were still left on the edges.

That is, when your fingers are almost dry but not completely dry, some residual fingerprints are still left on them.

A simple reconstruction of the crime scene reveals that the killer wiped his hands with the curtains after killing two people and was preparing to go upstairs.

Because of the excessive force used in the early stages, the murderer stabbed the victim Zhang Guoyi and his wife more than a dozen times, to the point that the gloves were soaked with blood. He had to take off the slippery gloves, wipe his hands again, and take a towel to tie the knife to his hands. The reason these steps could be confirmed was based on the state of the blood dripping at the scene.

Using conventional fingerprint identification methods, whether the fingerprints are collected from curtains or towels, they are generally not very useful.
If the fingerprint is so damaged that even three or five feature points cannot be marked, the number of candidate fingerprints generated when comparing them in software will be enormous.

Using a high-definition spectral imager would be better; I was able to get more than four feature points from the fingerprints along the edge of the curtains. The fingerprints on the towel were of much lower quality, yielding only about three, or at most four, feature points.

Jiang Yuan then focused on curtains.

Based on the principle that 7 is feasible and 8 is feasible, the distance of 4 or 5 feature points is still a bit far. At this time, we need to use image enhancement technology to try to add one or two more feature points on the basis of 5 feature points.

The process was so fast that even the two fingerprint experts, Liu Changhe and Lin An, soon felt dizzy.

Image enhancement is a very counterintuitive operation. Even basic grayscale is a numerical way of determining the image. If you're not a professional, just watching Jiang Yuan's operation process will only leave you confused.

Liu Changhe and Lin Anjia together had a level 0.5 image analysis skill, but watching Jiang Yuan's operation only made them feel dazed and excited.

This is exactly the kind of Jiang Yuan they want!
If they were just ordinary fingerprint experts, why would they need to come to Anwan? The two of them could handle it themselves.

Jiang Yuan worked at the computer for a while, then got up and drew the curtains to collect images of the evidence.

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

As the group busied themselves, Liu Zhuangshi, the head of the criminal investigation team, walked in.

"Oh, are you taking fingerprints again?" Liu Zhuangshi felt his anxiety ease as he watched them working hard.

Although he was so destitute that he had to beg for money everywhere, the funds he had finally managed to obtain were not wasted; instead, they were being spent by a genius detective like Jiang Yuan. Thinking this way made him feel exceptionally at ease.

"There's a fingerprint here that seems promising," Jiang Yuan explained to Liu Zhuangshi simply, as there was no need to explain further.

Liu Zhuangshi nodded repeatedly and said hurriedly, "That's great. There's a high probability that the Cuiling 211 case was committed by a habitual offender who travels around committing crimes. If we can find the fingerprints, the probability of a match should be very high."

He was just saying nice things. For Jiang Yuan and the others, the most worrying thing about this case was whether the murderer's fingerprints were in the fingerprint database.

But as Liu Zhuangshi analyzed, since the murderer in the Cuiling 211 case wasn't seeking revenge, the probability of a habitual offender committing crimes on the run is very high. This is because the murderer's process of killing was both bold and cautious. After killing the couple upstairs, he specifically cleaned his hands, wrapped them and the knife in a towel again, and then painstakingly went upstairs to kill the child and grandmother... This process is difficult to fully grasp without a trip to prison.

Jiang Yuan nodded slightly and said, "It's still uncertain how many feature points we can draw. If we can draw seven, that would be excellent..."

“Just like in the previous case, you make a list of suspects, and I’ll send someone to collect their fingerprints again…” Liu Zhuangshi has already started to rely on this approach.

Jiang Yuan grunted in agreement and said, "I plan to use the footprints to filter through them first. That way, even if only six feature points are marked, we can still make a usable list."

Not only Liu Zhuangshi, but also Liu Changhe and Lin An looked over and said in unison, "It can even be paired with footprints?"

“This case is covered in bloody footprints; it would be a shame not to use them,” Jiang Yuan said, marking fingerprints again.

Liu Zhuangshi pressed further, "Can the footprints determine how far we've progressed?"

Jiang Yuan said without even looking up, "Judging from the time of the incident, the murderer should be a male around 23 years old, about 1.75 meters tall, weighing 150 kilograms. He has size 42 feet, and his shoes are half a size too big. He is also pigeon-toed."

"This is good, this is good..." Liu Zhuangshi nodded repeatedly, his expression relaxing, and he even had the thought that this case was nothing special.

Of course, this thought only crossed my mind for a moment. The reason why the Cuiling 211 case became a major case was because several investigations failed to make a breakthrough. Just looking at old photos and old evidence, one could say that the case has been solved. Anyway, Liu Zhuangshi didn't have the guts to do that.

The members of the Jiangyuan unsolved case task force were surprisingly positive; upon hearing the news, they immediately began signing up in their small group chat.
[Shouldn't we implement a rotation system? Those who have been there before shouldn't have to work so hard; let those who haven't been go yet take turns.]

[I volunteered to travel to remote, impoverished, and underdeveloped areas.]

[You're thinking too optimistically; it's easier to win in remote, impoverished, and underdeveloped areas!]

During a relaxed chat, Wang Chuanxing initiated a lottery, initially selecting 8 people. If more teams were formed later, another lottery would be held.

In a warm and friendly atmosphere, Jiang Yuan completed the final feature point annotation.

With 6 feature points, the computer automatically runs through the database, and at least tens of thousands of fingerprints meet the criteria. Under normal circumstances, it is meaningless to investigate, because behind these tens of thousands of fingerprints, there are many more secondary fingerprints with slightly lower similarity.

However, when the results of footprint identification are cross-referenced, the number of fingerprints that meet the criteria is instantly reduced to a few dozen.

This quantity is neither too much nor too little, but it is enough for operation.

Liu Changhe and Lin An exchanged a glance, their eyes filled with excitement. This case was an ordinary one for Jiang Yuan, but a major case for the Anwan City Public Security Bureau. For them, it could be considered a breakthrough in their careers.

"48 groups. If each group still has 4 people, I'll have to request some reinforcements," Liu Zhuangshi said, though his expression remained relaxed. For such a big case, sending out 200 people was nothing.

Of course, the detailed calculations are also quite alarming. The daily allowance for 200 people is 36,000 yuan, and if they go out for three to five days, the expenses will be close to 200,000 yuan. The round-trip fuel or airfare costs are even more substantial. Even if they are all police officers from the same unit, spending 2 million yuan on travel expenses for 200 people would be considered a saving.

At this crucial moment, Liu Changhe, an insider, immediately said, "If there are financial difficulties, I can help apply for subsidies from the ministries..."

Lin An also said, "If you have any testing-related requests, you can send them directly to our laboratory. They will charge the lowest fee there, which should save you some money."

Li Zemin, who has been working on the front lines for many years, also knows how to save money. He said, "We can also consider marking these 48 people first, prohibiting them from leaving the country, and then checking their criminal records. If we come in two batches, the burden on personnel and travel expenses will be much smaller. There may be several suspects in a province or a city. They don't know that we are investigating the Cuiling 211 case, so the order of arrival should not have any impact."

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

Ultimately, the case is handled by the Anwan City Public Security Bureau, which is an independent entity; we can't expect too much from them.

Liu Zhuangshi gritted his teeth and said, "It's safest to take them all out at once. We finally have a chance... As for the people, we can borrow some young people. As for the money... I'll talk to the director!"

(End of this chapter)