Chapter 6: Fingerprint Identification

The Criminal Police Team's yard was much quieter than usual.

In a county like Ningtai with a population of several hundred thousand, the likelihood of major cases occurring wasn't high. Throughout the year, there were only about ten to eight unnatural deaths, and among those, the ones that ended up being criminal cases, namely murder cases, were usually only one or two.

That was why, even though this case seemed simple, the Criminal Police Team was in full deployment mode.

When Jiang Yuan returned to the office, he saw that the fourth floor where the Criminal Investigation Division was located was empty, except the door to the trace evidence office was open, with someone busily typing away at their keyboard inside.

"Make sure to write a detailed report. This case might end up a death penalty case, and the requirements for a capital review are very strict." Wu Jun reminded Jiang Yuan and then added, "Back when we worked on a case, there was a piece of evidence that was a plastic oil drum. Two years had passed since we closed the case, and suddenly we got a call asking why the drum in the picture was white, but the actual evidence was yellow."

As he booted up his computer, Jiang Yuan listened and asked curiously, "Why?"

"Why? Because the actual evidence had aged and the plastic had changed color. We had to make supplementary materials." Wu Jun paused and then continued, "The point of telling you this is to say that the verification for death penalty cases is much stricter than for other cases. Lots of eyes are watching, so it doesn't hurt to set a higher standard."

"Understood," Jiang Yuan agreed smoothly. After a pause, he asked, "Should I avoid involvement because of my relationship with Seventeen Uncle...?"

"Only close relatives need to do that." Wu Jun's definition of close relatives varied within different legal texts. The scope was broadest in administrative law and narrowest in Criminal Law, limited to spouses, parents, children, and siblings.

Reassured, Jiang Yuan focused on his work.

Soon, his desk was neatly covered with a series of photos.

Seventeen Uncle's intestines, Seventeen Uncle's heart, Seventeen Uncle's brain slices, Seventeen Uncle's stomach contents... Jiang Yuan carefully selected and labeled them.

For the police officers, the complexity of case processing often far surpasses that of solving the case. Just like with the current homicide, even if the case details were simple and clear, and the suspect confessed, there was still a countless number of paperwork to be done during the processing phase.

It wasn't until close to the end of the work day that noise started to drift in from the yard.

Jiang Yuan looked outside the window and saw that all three cars from the Criminal Police Team had returned; Captain Liu of the second squad even stood in full gear in front of the middle police car as if he were preparing for battle.

Seventeen Auntie was thin and had a blank look in her eyes as she was handcuffed and shuffled out from the back seat.

To be honest, Jiang Yuan didn't have many good or bad memories of Seventeen Auntie. Before he took his civil service exams, he had studied medicine in another city for five years. Even before that, he had spent three years at a boarding high school, so his impression of Seventeen Auntie was much less vivid than his impression of Seventeen Uncle's belly...

"The suspect has identified the murder weapon as a chef's knife, which was thrown into a trash can outside the community," Wu Jun stood up to look downstairs and took the opportunity to update Jiang Yuan on the case.

Jiang Yuan exhaled slowly. With the case progressing to this stage, solving the case was basically concluded, particularly for those where the murder weapon was discarded and then identified separately, which was many times more difficult to overturn than those based solely on confessions.

"What about disposing of the body? She couldn't have moved it alone, could she?" Jiang Yuan asked another question.

"Her brother helped move it, using the tricycle and cart from their shop to transport vegetables," Wu Jun paused and then added, "He's been caught too and has confessed."

With that, the case had both physical evidence and confessions, making it a near ironclad case.

As Jiang Yuan's thoughts wandered, a semi-transparent system interface popped up.

Task: Perform a comprehensive autopsy to assist in solving the case.

Task reward: Chongqing Single Finger Fingerprint Analysis Method — Loop Pattern Identification (LV3).

Jiang Yuan's eyes widened at the sight and then watched as a silver dumpling flew into his forehead.

A flood of information aggressively forced its way in.

The Chongqing Single Finger Fingerprint Analysis Method was one of the single finger fingerprint analysis methods and was one of the first to be adopted in China. It is specifically used to deal with situations where there is only one fingerprint of a finger or even just a fragment of a fingerprint. Similarly, there are several other methods, including the Qingdao Single-Finger Fingerprint Analysis Method in China, and the Bartley Single Finger Fingerprint Classification Method in other countries. There is no superior or inferior method; they primarily differ in the way fingerprints are categorized and classified, and the analysis methods vary slightly.

In simple terms, it was a technique for matching fingerprints.

Jiang Yuan's eyes gleamed with excitement. Fingerprint matching was the hallmark of trace evidence investigation, and indeed, it took significant time and effort to learn. The system's direct offering greatly increased his sense of happiness.

But matching fingerprints wasn't an easy task.

Those devices that supposedly take any random fingerprint photo, enter it into the computer, and whirr away to find a matching print don't yet exist.

The established fingerprint automatic identification technology (AFIS) used internationally, whether it's Japan's NEC, the United States' COGENT, or France's Morpho, all involve manually marking the features of the fingerprint found at the scene, that is, what's known as feature points. Then they match these feature points automatically in the system and score them according to similarity, from highest to lowest, to produce a list of candidates for review.

This is because fingerprints can be deformed due to pressure and other factors, often in a nonlinear way. Many times, fingerprints can also be translated, overlapped, and poorly preserved, which is all too common. Moreover, fingerprints found at a crime scene are frequently incomplete.

In short, fingerprint automatic identification technology requires manual preprocessing of the fingerprints.

Devices like employee time clocks only know how to match two fingerprints to determine if they are the same, but their recognition rate is nowhere near what the police need.

At this moment, Wu Jun only saw Jiang Yuan with a distracted look and gently coughed twice, saying, "There's nothing much to do now. If you want to leave, go ahead; I'll handle the rest."

"Uh... is that okay?" Jiang Yuan hesitated. He wanted to try out the new technology he had acquired but thought that trying it at home would not be an issue either.

"We just have this much work; when it's done, it's done," said Wu Jun, proudly lifting his chin. Compared to the police officers below who were just starting to get busy, the forensic doctor's busy work had already ended.