National Forensic Doctor

In the afternoon, after a little tidying up, Jiang Yuan and Wang Zhong each rode their own small electric bicycles to the area where the crime occurred.

The small red brick building located in the suburbs still has a contemporary style. The small two-way four-lane road has large trees of questionable species planted on both sides and in the middle. The sparse shrubs prove that the level of maintenance nearby is very average, but it took time to plant them. The trees still maintain the basic quality of the residential area.

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

Of course, it's just prosperity rather than prosperity. Looking around, you can see a patchwork of old residential areas and new temporary buildings, keeping the environment at the level of an old industrial area.

Small shops and small shops are the mainstream business model in the neighborhood. Most of the shop fronts are old-fashioned, which makes it difficult to stimulate people's desire to consume.

And these shops that don't even bother to clean up their door curtains also have no desire to install cameras.

Municipal construction here seems to have stopped with time. The old road traffic is still well maintained, but it is only maintained to the extent it was back then, and newer or better things are almost non-existent.

The neighborhood where the crime occurred appears to be more desolate than other neighborhoods on the same road. Only at the main entrance, a few old men gathered, looking at everything around them with suspicion. The other two gates of the community are now cuffed with large chains. These measures, which were originally convenient measures, are now regarded as the main culprits.

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

"Police." Both of them had changed into civilian clothes, so they took out their police officer ID cards and took a look at them.

The old man frowned: "I heard that there are people who specialize in making fake police certificates to deceive people. Are you a liar..."

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

The old man took out his mobile phone and was about to call 110. He was stunned when he heard: "What?"

"Let's go in and look at the scene to see if there is any evidence. You can just stand inside and watch, and then just sign." Wang Zhongyan explained briefly and comprehensively.

China’s witness system for on-site investigation of criminal cases requires that the investigation agency must invite a third-party natural person to witness the investigation and inspection activities at the crime scene. This is completely different from the American judicial system that often appears in movies and TV dramas.

The United States adopts the method of police self-certification, which stipulates an on-site recording system and requires police to self-certify the fairness and standardization of on-site investigations. In contrast, RB and Russia also adopt on-site survey witness systems, but they are different.

To put it simply, countries with a witness system require that the evidence collection in each case be watched by outsiders, so as to prevent the occurrence of perjury as much as possible. Countries like the United States, which do not have a witness system, require each police officer to exercise self-restraint. Once perjury occurs, all cases handled by the police officer can be questioned.

Although there are often imperfections in practice, as small police officers, Wang Zhong and Jiang Yuan both performed in accordance with the regulations.

In fact, just looking for one or two passers-by is still not very consistent with the spirit of the on-site investigation witness system. Fundamentally speaking, this system requires that the witness have a certain understanding of the scene, a certain understanding of the criminal investigation, and be related to the case. It would be better if unrelated personnel can witness the inspection site multiple times throughout the process.

However, at a time when the masses do not understand, there is no financial compensation for witnesses, the police are very busy, and the judicial system does not have high requirements, such a request is obviously unrealistic, and the police are more willing to find someone who is obedient and sensible, does not hinder the investigation, and does not interfere with the investigation. Witnesses who will leak information.

Two old men who are under retirement age but started their retirement life early due to the decline of their companies are quite good. It is also more compliant than using auxiliary police officers as witnesses.

The old men at the door might be busy hatching eggs, or they might be interested in the murders in the community. After asking for a while, they reluctantly watched the two young old men go to the scene of the crime. of the building.

Wang Zhong took the key from the office, opened the security tape, opened the door and entered, then locked the door and changed clothes. Two old men who were under age but actually retired were asked by him to stand in the corner and were not allowed to speak, move, or take pictures.

"Where do we start?" Wang Zhong was originally not planning to come, and he didn't have the confidence to come over for re-examination, but Jiang Yuan had an idea, so he came anyway.

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

Following his words, the system slowly unfolded a translucent interface:

Mission: Start from scratch

Task content: Repeat the investigation 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 felt a little stupid, then he leaned close to Jiang Yuan and whispered: "Is it necessary?"

"Give it a try." Jiang Yuan said, laying out the equipment, picking up a glass from the shoe cabinet at the door, soaking some water with a cotton swab, and gently wiping it.

Although we have known each other for a while, my qualifications are a bit deeper. But deep down, Wang Zhong was convinced of Jiang Yuan. For skills like fingerprinting, the difference in strength is too easy to show.

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

Ordinary investigators wipe cups, or in other words, when investigators in Ningtai County wipe cups, they directly wipe a circle along the rim of the cup with a cotton swab. Although this method can also wipe out possible DNA, it has never been It's all just a simple approach. In other words, it is a common practice of insufficient ability.

Jiang Yuan's rubbing method was something Wang Zhong had only seen on rare occasions. Jiang Yuan first dipped the cotton swab in water and then squeezed it until it was half dry. When wiping, he would not wipe a large area. Instead, he would choose a position at the mouth of the cup, rub the cotton swab up and down, and rub it evenly three to four times, trying to wipe away any DNA that may be present on it.

After wiping one spot, Jiang Yuan wiped a certain spot again at intervals, and after doing this many times, he completed the extraction of DNA from a cup.

Doing this will naturally take much more time than wiping it all around, but the probability of extracting DNA is also much higher.

Although Wang Zhong had never tried Jiang Yuan's method of wiping DNA before, from the various details Jiang Yuan showed, Wang Zhong knew that Jiang Yuan's rank was really higher than the current survey in the team.

For example, a semi-dry cotton swab is easier to transfer DNA than a dry-rubbed cotton swab, and it is also easier to transfer DNA than a cotton swab soaked in water. The so-called does not mix with mud and does not touch water.

To use the way northerners understand it, cotton swabs are like bath towels. If you rub dry skin with a dry bath towel, you won't get much out of it. A bath towel soaked in water will just slide around. If you can't remove much dirt by rubbing, you have to use a semi-dry bath towel and rub the skin with a semi-dry but not wet towel. This will have the best effect and can remove the most dirt.

To give an example in a way that non-Northerners understand, cotton swabs are like tongues. If you wipe your tongue dry and lick dry skin, you won't be able to lick much. The effect of moistening your tongue with water is not good either. The best effect is to lick the semi-dry skin with a semi-dry tongue and the best friction.

Similarly, Jiang Yuan's wiping method of determining a spot is much more effective than wiping in a circle. To give an example in the same way as northerners understand it, it is like using a bath towel to rub at specific points, or using a bath towel to pull a big saw. What comes out cannot be ignored. To use the way non-Northerners understand it, for example, licking one spot is more effective than licking all over the place.

Jiang Yuan really had something, so Wang Zhong stopped talking and simply followed Jiang Yuan and attacked him.

After working in the criminal inspection squadron for several years, Wang Zhong has long understood that just because you understand something when you see it, or even understand it well, does not mean that you can imagine it, and that it does not mean that you can understand it. If you use it correctly, it doesn't mean you can use it well, and using it well doesn't mean you can use it quickly.

To give an example in a way that everyone who has participated in nine years of compulsory education can understand, there are only 5 formulas in Euclidean geometry, and 100 formulas in Newton's three laws. Normal people can understand it after listening to the class, but they may not be able to understand it when they see the questions. No matter which formula you use, it may not be correct even if you think of it. If you use it correctly, you may not be able to use it well. If you use it well, you may not be able to use it quickly.

Wang Zhong also appeared at the site all year round to conduct surveys. Seeing that Jiang Yuan could do so meticulously, well and quickly, he was even surprised. Fortunately, when doing fingerprints, he got used to doing it for Jiang Yuan. Once it was familiar, it gradually became smoother. As he did it, he even felt quite comfortable.