In the afternoon, after a little preparation, Jiang Yuan and Wang Zhong each rode their own electric scooters to the crime scene in the small community.

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

This is the far suburbs of the county, but because of the nearby factories, it is more prosperous than many places in the county.

Of course, it is only prosperous, not prosperous. Looking around, the old residential areas and new temporary buildings maintain the environment at the level of an old industrial area.

Small shops and stores are the mainstream business model nearby, and the storefronts of these small shops are mostly old-fashioned styles, which are difficult to stimulate people's desire to consume.

And these stores that are too lazy to even tidy up their curtains also have no desire to install cameras.

The municipal construction here seems to have stagnated with time. The old road traffic is still well maintained, but things that are perhaps better updated have hardly appeared.

The crime scene community appeared more desolate than other communities on the same road. Only the main entrance gathered a few old men, looking suspiciously at everything around them. The other two gates of the community have now been chained up. These measures that were originally for the convenience of the residents are now seen as the culprit.

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

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

The old man frowned, "I heard that there are people who make fake police badges to deceive others. Are you a fraud...?"

"If you don't believe it, call 110." Wang Zhong said, and then said, "We are here to revisit the scene. Do you want to be a witness?"

The witness system for criminal scene investigation in China requires the investigating agency to invite a third-party natural person to witness the investigation and inspection activities of the crime scene. This is completely different from the American judicial system that often appears in movies and TV shows.

The United States uses a self-certification system for police officers, which stipulates a system of on-site recording and requires police officers to certify the fairness and standardization of on-site investigation. In comparison, Russia and China also use the witness system for on-site investigation, but they are different in their own ways.

In short, in countries with a witness system, the system requires that every case be examined with an outsider present to minimize the possibility of false testimony. In countries like the United States that do not have a witness system, every police officer is required to self-restrain. Once false testimony occurs, all the cases handled by the police officer can be suspected.

Although there are often imperfections in practice, as a small police officer, Wang Zhong and Jiang Yuan both follow the rules and regulations.In fact, finding one or two random passersby still doesn't quite fit the spirit of the witness system for on-site investigation. Essentially, this system requires finding someone who has a certain understanding of the crime scene and criminal investigation but is not related to the case to be a witness. If they can witness the on-site investigation multiple times throughout the process, that would be even better.

However, in a society where the public is not knowledgeable about this system, witnesses are not economically compensated, the police are busy, and the judicial system has low requirements, such demands are obviously impractical. The police would rather find witnesses who are obedient, cooperative, and do not interfere with the investigation or leak information.

Two old grandpas who were not yet retirement age but started their retirement early due to the decline of their business were good enough. It was much more compliant than using auxiliary police officers as witnesses.

The several old grandpas at the door may have been idle or perhaps were interested in the homicide in the community. After a good while of questioning, they reluctantly watched the two young old men enter the building where the crime occurred.

Wang Zhong took the key from the office, lifted the police tape, opened the door, entered, and then changed his clothes and locked the door. He demanded that the two old men who were not yet retired but actually retired stand in the corner, not speak, move, or take photos.

"Where do we start?" Wang Zhong wasn't planning on coming, and he didn't have much confidence in doing a re-investigation, but Jiang Yuan had ideas, so he followed.

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

As he spoke, a translucent interface slowly unfolded from the system:

Mission: Start from the beginning

Mission content: Conduct a repeat investigation of the Xue Ming case scene to obtain clues and evidence.

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

"Start from the beginning?" Wang Zhong listened a bit foolishly and then leaned closer to Jiang Yuan and whispered, "Is it necessary?"

"Let's give it a try." Jiang Yuan said as he set up his equipment and picked up a glass from the shoe cabinet at the entrance. He dipped a cotton swab in water and gently wiped it.

Although they had known each other for a while, Jiang Yuan's qualifications were deeper. But fundamentally, Wang Zhong was convinced of Jiang Yuan. The difference in skill level, such as fingerprinting, was too easy to show.

After standing still for a moment, Wang Zhong was speechless at Jiang Yuan's movements.

Ordinary on-site investigators wipe the glass by running a cotton swab along the rim of the glass. Although this method can also wipe off possible DNA, it has always been a simple method, or rather, a commonly used method for those with insufficient ability.

Jiang Yuan's wiping method, however, was one that Wang Zhong had only seen in very few situations. Jiang Yuan first dipped the cotton swab in water, then squeezed it until it was half-dry. When wiping, he did not wipe a large area but instead selected a position on the rim of the glass and rubbed the cotton swab up and down, wiping three to four times with even force, trying to wipe off any possible DNA.

After wiping a spot, Jiang Yuan would wipe another spot at a certain distance, and repeat this process several times before completing the extraction of DNA from a glass.

Although this method took more time than circling around the glass, the probability of extracting DNA was much higher.Although Wang Zhong had never tried the DNA swabbing method used by Jiang Yuan before, he could tell from Jiang Yuan's performance that his level was higher than that of the on-site investigators in the team.

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For example, a semi-dry cotton swab is more likely to transfer DNA than a dry one or one that is fully soaked in water. It should not be muddy or wet.

In the way that Northerners understand it, a cotton swab is like a washcloth. Rubbing dry skin with a dry washcloth will not remove much dirt, and a wet washcloth will only slide around and not remove much grime. The best way is to use a semi-dry washcloth to rub semi-dry skin, which will produce the best results and remove the most dirt.

In the way that non-Northerners understand it, a cotton swab is like a tongue. Licking dry skin with a dry tongue will not remove much dirt, and a wet tongue will not be very effective either. The best way is to use a semi-dry tongue to lick semi-dry skin, which will produce the best friction.

Similarly, Jiang Yuan's method of wiping a specific point is more effective than wiping around in a circle. Using the way that Northerners understand it, this is like using a washcloth to rub a specific point instead of pulling back and forth to remove dirt. Using the way that non-Northerners understand it, licking a specific point is more effective than licking randomly all over.

Wang Zhong knew that Jiang Yuan had the skills, so he followed him and assisted him.

After working for several years in the forensic department's trace detection position, Wang Zhong understood that just because you see something and understand it doesn't mean you can think of it, and even if you can think of it, it doesn't mean you can use it correctly. Even if you use it correctly, it doesn't mean you can use it well, and even if you use it well, it doesn't mean you can use it quickly.

Using a way that someone who has completed nine years of compulsory education can understand, Euclidean geometry has only five formulas, and Newton's three laws have only a few dozen characters. Normal people can understand them after listening to the lesson, but when they see the problem, they may not know which formula to use, and even if they do, they may not use it correctly. Even if they use it correctly, they may not use it well, and even if they use it well, they may not use it quickly.

Wang Zhong was also often present at the scene of investigations, and he was amazed at how meticulous, good, and fast Jiang Yuan was. Fortunately, when they were doing fingerprinting, he had already gotten used to assisting Jiang Yuan, and it gradually became smooth. As they worked, he even felt quite comfortable.