National Forensic Doctor

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

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

At the same time, urine can provide a lot of information. Hospitals can use it to do urine tests, and criminal departments can also use it to test DNA.

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

However, laymen know the ropes, and experts cannot pretend to be confused.

Although it is possible to extract DNA from urine, the difficulty is much higher than that from blood. First, the number of exfoliated cells contained in urine is relatively small, which requires more urine to facilitate extraction.

On the other hand, the urine at the scene was obviously poorly preserved. Good urine suitable for DNA extraction should be stored at low temperature.

Therefore, in the era when DNA technology was first promoted, that is, in the first decade of the 21st century, it was basically very difficult to extract DNA from urine, and there were very few similar cases. At that time, DNA comparisons were mainly based on blood and rice juice. Thirdly, it also had to be oral epithelial cells such as toothbrushes and cigarette butts. Occasionally, there were some hairs, and they had to have hair follicle tissue.

Nowadays, technology has improved, and the richness of DNA comparisons has become much higher. Not only does hair no longer require hair follicle tissue, the awesome DNA laboratory also has very low requirements for extracting DNA from urine. By the way, a little trivia: If a man or woman suspects that the child is not theirs, there is no need to take the child to an institution, and there is no need to draw blood to leave traces. He or she can just take the child to pee the urine that can be collected, and use ice coke to calm it down. Send it to the relevant testing agency and you will get the results soon. 47 It is naturally more convenient for criminal suspects. Jiang Yuan used a wet cotton swab to collect as many urine spots as possible, then combined several cotton swabs together, wrapped them in filter paper, and folded them into a beautiful triangle.

This method can maximize the integrity and original flavor of urine, just like extracting blood spots.

Several trace inspectors from Chiyong City looked at Jiang Yuan's operations and were a little confused about his methods.

To be honest, there is nothing mysterious about Jiang Yuan's operation this time. It is the most basic and cautious approach, and few people can say whether it is good or bad.

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

Let the DNA lab rush it. Jiang Yuan handed the urine sample to the trace examiner at the back and continued searching in the bathroom.

Liu Jinghui interrupted at this time, saying that there is a 90% chance that this person has a strong connection with the case and is probably a participant or insider in the case.

The detachment leader was only concerned about the case and immediately asked: How to say it?

Liu Jinghui said, this is the den of the three-person gang. It should be said that this is where they prepare to rob and dispose of the stolen goods. Except for the three people and the participants, it cannot be used to entertain guests.

The detachment leader nodded repeatedly. He is not a police officer who is particularly good at solving crimes. In other words, he has certain criminal investigation abilities, but he focuses on management and has gradually become separated from front-line leadership. The detachment leader himself didn't believe himself when he was asked to make similar judgments. But after Liu Jinghui said it, the detachment leader's mood immediately changed.

So, there should actually be four criminals? The detachment leader exhausted his brainpower and calculated 3+1.

Liu Jinghui glanced at Jiang Yuan and said with a smile: "The crime scene, which is the victim's home, must be three people. As for the owner of the urine just found, I guess, guess, it must have been stolen." 1

The detachment leader was stunned and said, "You're the one who sold the stolen goods?" Why?

This answer was somewhat biased. Liu Jinghui slowly explained: First, this person does not seem to be an accomplice. The three suspects are all young enough to pee in the wind, and they are all young men who can fight and fight hard. This guy can run around every time he pees. What's the use of having such an accomplice? Just give him some money.

Second, let’s talk about the possibility of being the mastermind behind the scenes. But judging from the safe, he did not provide corresponding items, such as oxygen cutting machines. If there is a curtain,

If it was the envoy later, he should buy it or borrow it. But our investigation has made it very clear that the three of them went to the car scrapping factory to buy an oxygen cutting machine, which also shows that the three of them neither believed each other nor this person.

third. This man appeared at the foothold of the three-person gang, it must be because the three of them needed him, otherwise they would not have told him his location. What do those three young men who have just committed a major crime and are about to run away need most? It's nothing more than money, documents, and a plan to escape.

When Liu Jinghui said this, he raised his chin and said: Although from our point of view, the documents and escape plan are definitely more difficult. But in fact, the most valuable and hardest to obtain is still money. The victim had very little cash at home, and the main items missing were jewelry, gold, watches, and toys... The three of them had to convert these things into money before they could escape. Therefore, what they needed most at this time was someone who could sell the stolen goods.

It makes sense, it makes sense... The detachment leader nodded repeatedly. He now saw hope of solving the case. He felt very comfortable listening to Liu Jinghui's words again.

The conversation between the two ended, and the room fell silent for a while.

Liu Jinghui and the detachment leader both frowned.

This atmosphere is wrong.

When investigating a crime scene, it is normal for someone to talk from time to time, or even chat. It's like you picked up a condom, and I picked up a piece of hard toilet paper. Everyone hand it over.

After a while, you can determine whether there was one session or two sessions in the room.

Just now, several trace inspectors followed Jiang Yuan and kept muttering in low voices, like the background sound in the forest. The sudden silence at this moment was like the sudden silence in the forest, which was obviously unreasonable.

Liu Jinghui and the detachment leader moved forward and saw a few birds at the door of the bathroom... no, several trace inspection comrades, stretching their necks to look at something.

Going further inside, I saw Jiang Yuan holding a tablet in his hand and making gestures.

What is this... doing? The detachment leader asked curiously.

The separation of overlapping fingerprints... The oldest tracer looked back at the detachment leader, with a trace of despair clearly in his eyes.

The detachment leader was stunned: Did he find an overlapping fingerprint? How were they separated?

That’s right. Trace Check repeated.

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

I found several fingerprints on the toilet, and they all overlapped when I took them out. I wanted to separate one out first to see if I could match the fourth person. What Jiang Yuan said is very simple.

There are many fingerprints in this rental house, and it is also very messy. Considering that the three-person gang had only rented the house for a short period of time, it is conceivable that most of the fingerprints in the house may come from the landlord, previous tenants, and others.

Although it was possible to collect all these fingerprints and compare them together before screening them, Jiang Yuan had many means and was not willing to wait that long.

After all, now that DNA has been collected and it is the most convincing evidence, the main purpose of collecting fingerprints is to make it faster.

A pursuit like this can take almost an hour, and the murderer must not be given a chance to breathe. Only by making the fugitive feel suffocated can the pursuit be successful.

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

The fourth person peed in the toilet. Normally, he would press the flush button. Therefore, there is a high probability that the flush button will have the fingerprint of the fourth person.

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

The problem at this time is that the overlapping fingerprints cannot be distinguished at all, let alone matched by software - but this is only the understanding of ordinary fingerprint examiners.

At Jiang Yuan's level, if he wanted to, he could separate fingerprints through texture features.

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

It's just that this scene is really heartbreaking for ordinary trace inspectors to watch - this kind of technique is difficult to learn without some talent and God's blessing.

That's Jiang Yuan, too

It is a texture-by-texture analysis.

Current fingerprint technology can theoretically decompose overlapping fingerprints through software, but the error rate is too high and the resolved overlapping fingerprints are basically unusable. When you meet a knowledgeable lawyer or something, it's easy to get slapped in the face right there in court.

At this time, the most reliable method is manual work, which is extremely difficult.

Jiang Yuan made it easily with a tablet.

After marking two more sets of characteristic points, Jiang Yuan was soon in the top ten, winning one person in the competition.

Revhan. This person has a history of selling stolen goods, and he also deals in fake certificates... he has a complete range of categories. Jiang Yuannian looked at the information in the competition and felt that this person seemed to be tailor-made.

But the detachment leader slapped his thigh hard: Did the three-person gang buy the fake certificate from him?

Probably. Jiang Yuan nodded.

That must be it. Sell ​​the stolen goods and provide documents! The detachment leader couldn't wait.

If the identity documents of the trio were purchased from a fourth person, then catching Revhan would make it easy to determine the current location of the trio.

Once someone is arrested, the whole case will have a perfect ending.

The detachment leader became happier and happier as he thought about it. He picked up his phone and made arrangements.

At this point, Jiang Yuan agreed with his judgment. He turned to Mu Zhiyang and said softly: You can buy high-speed rail tickets and go home.