Chapter 24

In the afternoon, after tidying up a bit, Jiang Yuan and Wang Zhong each rode their own small electric scooters to the residential complex where the case occurred.

The red-brick building located in the suburbs still had quite a sense of the era. The small two-way, four-lane road was planted with trees of questionable variety in the middle and on both sides. The sparse shrubs proved that the maintenance level in the vicinity was quite average, but the trees planted over time still maintained the basic quality of a residential area.

This is the far suburb of the county, but because there are some factories nearby, it is actually more prosperous than many places in the county.

Of course, it is prosperous but not bustling. Looking around, patches of old residential complexes and new temporary buildings keep the environment at the level of an old industrial zone.

Small shops and stalls are the mainstream business model in the vicinity, and the storefronts of these small shops are mostly old-fashioned, making it difficult to arouse people's desire to consume.

And these shops, which are too lazy to even tidy up their door curtains, similarly have no desire to install surveillance cameras.

Municipal construction seems to have stalled here along with time. The old road traffic is still well-maintained, but it is maintained to about the level of that year, and things that are newer or perhaps better have almost not appeared.

The residential complex where the case occurred appears more desolate than other complexes on the same road. Only at the main entrance are a few old men gathered, looking at everything around them with suspicious eyes. The other two main gates of the complex are now locked with large chains. These actions, which originally belonged to convenience measures, are now seen as the root cause of the trouble.

"What are you doing?" Seeing Jiang Yuan and Wang Zhong riding their electric scooters to enter, an old man bravely blocked the road with his body.

"Police." Both of them had changed into plain clothes, so they took out their police IDs and showed them.

The old man frowned: "I heard that there are people who specialize in making fake police IDs to scam others. Are you scammers..."

"If you don't believe it, call 110." Wang Zhong said, then added: "We are here to re-examine the scene. Are you willing to be witnesses?"

The old man had already taken out his phone, ready to call 110, and was stunned when he heard this: "What?"

"We'll go in and look at the scene, see if there is any evidence left. You just stand inside and watch, and sign a paper when we're done." Wang Zhong explained concisely.

China's criminal case scene investigation witness system requires investigative agencies to invite third-party natural persons to witness the inspection and examination activities of the crime scene. This point is completely different from the American judicial system that often appears in movies and television dramas.

The United States adopts a police self-certification method, stipulates a scene recording system, and requires police to self-certify the fairness and standardization of scene investigation. In contrast, Japan and Russia also adopt the scene investigation witness system, but each has its differences.

Simply put, countries with a witness system require, in terms of the system, that the evidence collection of every case be watched by an outsider, so as to prevent the appearance of perjury as much as possible. Countries like the United States, which do not have a witness system, require every police officer to exercise self-restraint; once perjury occurs, all cases handled by that police officer can be questioned.

Although it is often imperfect in practice, as small police officers, Wang Zhong and Jiang Yuan both follow the regulations.

In fact, just finding one or two passersby is still not very consistent with the spirit of the scene investigation witness system. Fundamentally, this system requires finding personnel who have a certain understanding of the scene, a certain understanding of criminal investigation, and are unrelated to the case to act as witnesses. If they can witness the investigation of the scene multiple times throughout the process, that would be even better.

However, in the current situation where the masses do not understand, witnesses have no economic compensation, the police are busy, and the judicial system does not have high requirements, such requirements are obviously impractical, and the police are more willing to find witnesses who are obedient, sensible, do not hinder the investigation, and will not leak information.

The two old gentlemen who have not reached retirement age but have started their retirement life early due to the decline of their enterprises are quite good. They are also much more compliant than using auxiliary police as witnesses.

The old men at the entrance might be idle, or perhaps they were full of interest in the homicide in the complex. After a long inquiry, they reluctantly watched the two young old men enter the building where the crime scene was located.

Wang Zhong took the key from the office, casually lifted the warning tape, opened the door, entered, locked the door, and changed his clothes. The two old men who were not yet retired but were effectively retired were asked by him to stand in the corner, not allowed to speak, not allowed to move, and even less allowed to take pictures.

"Where should we start?" Wang Zhong originally didn't intend to come, and he didn't have much confidence in coming for a re-examination, but Jiang Yuan had an idea, so he followed.

Jiang Yuan looked around and said slowly: "Let's start from the beginning."

Following his words, the system's semi-transparent interface slowly unfolded:

Task: Start from the beginning

Task Content: Conduct a re-examination of the Xue Ming case scene to obtain clues and evidence.

Jiang Yuan stared at the system interface for a few seconds until it disappeared.

"Start from the beginning?" Wang Zhong was a bit dumbfounded, then leaned close to Jiang Yuan and whispered: "Is it necessary?"

"Let's try." Jiang Yuan said, setting out his equipment, then picked up a glass from the shoe cabinet at the entrance, dipped a cotton swab in a little water, and wiped it gently.

Although the time they have known each other is short and his own seniority is deeper, deep down, Wang Zhong is convinced by Jiang Yuan. For skills like fingerprints, the gap in strength is too easy to manifest.

And after standing still for a moment, Jiang Yuan's movements made Wang Zhong speechless.

Ordinary scene investigators wiping a cup, or rather, when the scene investigators of Ningtai County wipe a cup, they directly use a cotton swab to wipe around the rim of the cup. This method, although it can also wipe off possible DNA, has always been just a simplified approach. Or rather, it is a common practice when ability is insufficient.

Jiang Yuan's wiping method, however, is one that Wang Zhong has only seen in very few cases. Jiang Yuan first dipped the cotton swab in water, then squeezed it until it was semi-dry. When wiping, he would not wipe a large area, but would choose a position on the rim of the cup, move the cotton swab up and down, and wipe three to four times with even force, striving to wipe off the DNA that might exist there.

After wiping one point, Jiang Yuan would then move a distance away and wipe again at a certain point. Only after doing this multiple times did he complete the DNA extraction for one cup.

Doing it this way is naturally much more time-consuming than wiping around the rim, but the probability of extracting DNA is also much higher.

Although Wang Zhong had never tried this method of DNA extraction before, just from the various details Jiang Yuan displayed, Wang Zhong knew that Jiang Yuan's level was truly higher than the scene investigators in the team.

For example, a semi-dry cotton swab is easier to transfer DNA than a dry cotton swab, and also easier to transfer DNA than a cotton swab soaked with water. It is what is called not making mud and not sticking to water.

To give an example in a way that Northerners understand, a cotton swab is like a bath towel. Using a dry bath towel to scrub dry skin won't scrub off much, and a bath towel soaked with water will only slide around and won't scrub off much dirt. You have to use a semi-dry bath towel to scrub semi-dry skin; the effect is the best, and you can scrub off the most things.

And to give an example in a way that non-Northerners understand, a cotton swab is like a tongue. Wiping the tongue dry to lick dry skin won't lick off much either, and the effect of a tongue soaked with water is also not good. It has to be a semi-dry tongue licking semi-dry skin; the effect is the best, and it is the state with the best friction.

Similarly, Jiang Yuan's method of wiping a specific point is also much more effective than the method of wiping around the rim. Still using the example Northerners understand, this is like scrubbing a specific point with a bath towel versus sawing with a bath towel; the amount scrubbed off cannot be measured. And using the example non-Northerners understand, licking one point is more effective than licking everywhere.

Jiang Yuan really has the goods, so Wang Zhong didn't talk nonsense and simply followed Jiang Yuan to help him.

After working in the trace inspection position of the Criminal Science Squadron for several years, Wang Zhong had long understood that some things, when you see them, you feel you understand them, even understand them very well, but that doesn't mean you can think of them. Even if you think of them, it doesn't mean you use them correctly. Even if you use them correctly, it doesn't mean you use them well. Even if you use them well, it doesn't mean you use them quickly.

To give an example that anyone who has participated in nine-year compulsory education understands, there are only 5 formulas in Euclidean geometry, and Newton's three laws total only a hundred characters. Normal people can understand them after listening to the lecture, but when they see the problem, they may not think of which formula to use. Even if they think of it, they may not use it correctly. Even if they use it correctly, they may not use it well. Even if they use it well, they may not use it quickly.

Wang Zhong also frequently appears at the scene to conduct investigations. Seeing that Jiang Yuan can do it so meticulously, well, and quickly, he was simply too surprised to react. Fortunately, when doing fingerprints, he was used to helping Jiang Yuan. Once bitten, twice shy, he gradually became smooth, and as he did it, he even felt quite comfortable.