Chapter 359: The Fourth Person

Normal human urine is usually colorless, transparent, or slightly yellow. Although it contains a large amount of metabolic waste, it itself does not contain bacteria, so it can be drunk.

In addition, normal urine is weakly alkaline, so if people who pursue health must drink weakly alkaline water, urine can also be one of the choices.

At the same time, the information that can be provided in urine is also very large. Hospitals can use it for urine tests, and criminal science institutes can also use it to produce DNA.

Urine contains a small amount of exfoliated cells, and by using them, DNA comparison can be done.

However, laymen look at the doorway, and insiders cannot pretend to be confused.

DNA can indeed be extracted from urine, but the difficulty is much higher than that of blood and the like. First, the number of exfoliated cells contained in urine is relatively small, which requires a relatively large amount of urine to facilitate extraction.

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On the other hand, the urine at the scene is clearly of the type that is not well preserved. Good urine suitable for DNA extraction should be stored at low temperature.

Therefore, in the early days of DNA technology promotion, that is, the first 10 years of the 21st century, wanting to extract DNA from urine was basically very difficult, and there were very few similar cases. At that time, everyone compared DNA mainly based on blood and semen, and secondarily, it had to be oral epithelial cells like toothbrushes and cigarette butts. Occasionally, there were some hairs, but they had to have hair follicle tissue.

Nowadays, technology has improved, and the richness of DNA comparison has also increased. Not only do hairs not need hair follicle tissue, but top-notch DNA laboratories also have very low requirements for extracting DNA from urine.

By the way, here's a piece of cold knowledge: if a man or woman suspects that the child is not their own, they don't need to take the child to an agency, and they don't need to draw blood and leave traces. Just bring the urine that the child can collect, chill it with ice cola, and send it to the relevant testing agency, and they can get the result very quickly.

For criminal suspects, it is naturally more convenient. Jiang Yuan used a cotton swab dampened with moisture to collect as much urine as possible, then combined several cotton swabs together, wrapped them with filter paper, and folded them into a beautiful triangle.

This method can guarantee the integrity and original flavor of the urine to the greatest extent, which is the same as extracting blood spots.

Several Chiyong City trace investigators looked at Jiang Yuan's operation and couldn't figure out his path.

To be honest, Jiang Yuan's operation this time has nothing mysterious. It is the most basic and cautious practice. Several people can't tell whether it's good or bad.

However, the case seems to have made progress again, which is a very realistic result.

"Let the DNA laboratory rush it." Jiang Yuan handed the urine sample to the trace investigator behind him and continued to search in the bathroom.

Liu Jinghui interjected at this time: "This person has a 90% chance of having a strong correlation with the case, and is mostly a participant or someone in the know of the case."

The detachment leader only cares about the case now and immediately asked: "How so?"

Liu Jinghui said: "This is the hideout of the three-person gang. It should be said that it is the place where they prepare to rob and dispose of stolen goods. Except for the three of them, and the participants, it is impossible to be used to entertain guests."

The detachment leader nodded repeatedly. He is not a police officer who is particularly good at solving cases, or rather, he has a certain criminal investigation ability, but he is biased toward management and has gradually separated from the frontline leaders. Letting him make similar judgments himself, the detachment leader himself doesn't believe in himself, but Liu Jinghui said it, and the detachment leader's mood immediately changed.

"In this way, the actual perpetrators should have 4 people?" The detachment leader used his brain to calculate 3+1.

Liu Jinghui looked at Jiang Yuan and smiled: "At the crime scene, that is, in the victim's home, there must be three perpetrators. As for the owner of the urine just found, I guess... En, guess, it should be the one who disposes of stolen goods."

The detachment leader was stunned: "The one who disposes of stolen goods? Why?"

This answer was a bit off, and Liu Jinghui explained slowly: "First, this person doesn't look like an accomplice. The three criminal suspects are all at the age of being able to urinate ten feet in the wind. They are all young men who can fight and work hard. What's the use of having such an accomplice? Just sharing money with him."

"Second, it is said that there is a possibility of being the mastermind behind the scenes. But judging from the safe, he didn't provide corresponding items, such as an oxygen cutting machine. If there is a mastermind behind the scenes, he should be the one to buy or borrow it. But our investigation is already very clear. The three went to that car dismantling factory together to buy the oxygen cutting machine, which also shows that the three neither trust each other nor trust this one."

"Third. This person appeared at the hideout of the three-person gang. It must be because the three need him, otherwise they wouldn't tell him the location. What do the three young people who have just committed a major case and are preparing to run away need most? Nothing more than money, ID cards, and a plan to run away."

Liu Jinghui said this, raised his chin, and said: "Although from our point of view, ID cards and a plan to run away are definitely more difficult to obtain. But in reality, what is most valuable and most difficult to obtain is still money. There is very little cash in the victim's home. The lost items are mainly jewelry, gold, watches, cultural relics... The three must exchange these things for money to run away. So, what they need most now is the guy who disposes of stolen goods."

"Makes sense, makes sense..." The detachment leader nodded repeatedly. He now sees the hope of solving the case, and listening to Liu Jinghui speak, he feels incomparably pleasant.

The conversation between the two ended, and the room fell into silence.

Liu Jinghui and the detachment leader couldn't help but frown.

This atmosphere is wrong.

When investigating the crime scene, it is normal for people to talk from time to time, and even chat.

It's like you found a condom, I found a piece of hardened toilet paper, and everyone communicates to determine whether a shot was fired in the room, or two shots.

Just now, several trace investigators followed Jiang Yuan and kept whispering, like background sound in the forest. Suddenly, they stopped talking, as if the forest had suddenly become silent, which clearly didn't make sense.

Liu Jinghui and the detachment leader leaned forward and saw a few birds... no, several trace investigators, stretching their necks to see what.

Further inside, Jiang Yuan was holding a tablet, gesturing.

"This is... what are you doing?" The detachment leader asked curiously.

"Separation of overlapping fingerprints..." The oldest trace investigator looked back at the detachment leader, his eyes clearly revealing a trace of despair.

The detachment leader was stunned: "Is it finding an overlapping fingerprint? How to separate it?"

"That's what I'm saying." The trace investigator repeated.

Liu Jinghui looked at Jiang Yuan and asked in a low voice: "What are we doing now?"

"I found a few fingerprints on the toilet, and there are overlaps when taking them. I want to separate one first to see if I can match this fourth person." Jiang Yuan said it very simply.

There are many fingerprints in this rental house, and they are also very messy. Given that the three-person gang only rented it for a short time, it can be imagined that most of the fingerprints in the house may come from the landlord and the previous tenant, as well as the previous tenant, etc.

Although all these fingerprints can be collected, compared centrally, and then screened, Jiang Yuan has means, so he doesn't want to wait so long.

After all, DNA has been collected now, and it is the most convincing evidence. Then collecting fingerprints again, the main purpose is to be fast.

Pursuit is a matter of time. One hour is one hour. You must not give the perpetrator a chance to breathe. Only when the fugitive feels suffocated can the pursuit be successful.

In view of this, Jiang Yuan's choice is very simple. He directly took fingerprints from the flush button of the flush toilet.

The fourth person urinated in the toilet. Normally, they should press the flush button, so there should be the fourth person's fingerprints on the flush button.

At the same time, there will also be fingerprints of the other three, and even more people, on the flush button.

At this time, the problem is that the overlapping fingerprints cannot be distinguished at all, and cannot be matched by software—but this is only the understanding of ordinary trace investigators.

At Jiang Yuan's level, as long as he wants, he can separate the fingerprints through texture characteristics.

This process is not very easy, but Jiang Yuan can do it.

It's just that this scene makes ordinary trace investigators feel sad—this kind of technology, without a little talent, without heaven rewarding food, is very difficult to learn.

Even Jiang Yuan is analyzing it texture by texture.

Current fingerprint technology can theoretically decompose overlapping fingerprints through software, but the error rate is too high, and the decomposed overlapping fingerprints are basically unusable. When encountering knowledgeable lawyers, it is easy to be slapped in the face on the spot in court.

At this time, the most reliable is manual, and the difficulty is extremely high.

Jiang Yuan used a tablet to do it easily.

Then mark two sets of feature points, and soon, Jiang Yuan matched one out of more than ten.

"Lei Fuhan. This person has a record of disposing of stolen goods, and also concurrently operates fake certificates... the categories are very complete." Jiang Yuan read the matched information, only feeling that this person was tailor-made.

The detachment leader slapped his thigh hard: "Did the three-person gang buy fake certificates from him?"

"Very likely." Jiang Yuan nodded.

"It must be like this. Disposing of stolen goods and providing certificates!" The detachment leader couldn't wait.

If the ID cards of the three-person group were bought from the fourth person, then catching Lei Fuhan would easily determine the current location of the three-person group.

When catching people at that time, the whole case would be a perfect ending.

The detachment leader became happier the more he thought about it, picked up his phone, and made arrangements.

At this step, Jiang Yuan's judgment was consistent with his, and he just turned to Mu Zhiyang and said softly: "You can buy a high-speed rail ticket to go home."

... ===== CHAPTER 360 =====