National Forensic Doctor

After wiping the cups, wipe the glass. After wiping the glass, wipe the mirror. After wiping the smooth ones, wipe the coarse ones. After wiping the coarse ones, wipe the fine ones. After wiping the fine ones, wipe the soft ones. After wiping the soft ones, wipe the hard ones...

Exploration work, from a large perspective, is all kinds of things, but from a detailed perspective, it is all trivial and trivial.

The police all say that the investigation of cases is based on the accumulation of resources, which can be reflected during the on-site investigation.

For example, if you wipe DNA and fingerprints, laymen often think that as long as the suspect leaves DNA or fingerprints at the scene, he will be found by on-site investigators. But in fact, there are no advanced instruments in the world that can accurately detect All fingerprints and DNA within a certain range

For example, fingerprints are divided into three types: dominant, plastic and recessive. The former two can be seen, while the latter, as the name suggests, requires certain means to be seen. These methods also require different solutions depending on the location and material of the fingerprint. Or powder, or lines, or smoke, or chemical reagents, or different chemical reagents, or different chemical reagents…

In view of this, in order to obtain a fingerprint, the on-site survey or trace inspection personnel first need to determine where the fingerprint may exist, and then observe it. The observation method can be with the naked eye using light or angle, or by breathing on a smooth surface. The same can be done Use a magnifying glass or ultraviolet light to observe. After the location of the fingerprint is determined, the fingerprint can be extracted with powder, or chemically extracted with iodine fumigation or silver nitrate or other reagents.

Therefore, if a spider-man really climbed across the ceiling, the person doing the on-site investigation would most likely not find fingerprints on the ceiling.

DNA is even more troublesome than fingerprints.

After all, fingerprints can be seen, and sometimes DNA can be seen, but sometimes it can only be guessed.

As is common, when DNA is extracted from the victim's toothbrush, the police officer who does the extraction can't see anything. They can only guess that there is a high probability of DNA on the toothbrush.

If you switch to items with less high probability, such as shirts, sheets and other intimate clothing, or items such as drinking glasses and porcelain bowls, whether there is DNA on them is completely a matter of guessing.

The ability to do on-the-spot surveys is clearly demonstrated at this time. Some investigators think from the perspective of the criminal suspect, guessing the opponent's movements, so as to find possible clues, and paint them in an orderly manner; some investigators just collect shirts, sheets, etc. Pack it back, or just cut out a few pieces, regardless of whether it is really useful...

However, in general, the more people involved in the investigation, the more capable they are, the more time and energy they invest, the higher the probability of discovering clues and evidence.

Jiang Yuan's operating techniques seemed to Wang Zhong to be extremely strong, but he felt that it was more appropriate during the murder case. If it were a theft case, it would be almost impossible for Jiang Yuan to operate like this. The cost of making a tube of DNA is 100 yuan less for the reagents alone, and the number of times it can be done per unit time is even more limited. It is very likely that the line of biological test materials will not be able to queue up...

"Let's clean the bathroom again." Jiang Yuan took care of the bedroom, and the sky was already dark.

Wang Zhong patted his head after hearing this, pointed to a large box of evidence bags, and said, "Why don't we come back tomorrow? There are hundreds of copies of these. If they are all given to the laboratory, they will go crazy."

Jiang Yuan explained: "There are more than half of them. It is estimated that no DNA can be extracted, so no reagents can be used. The murderer did it too cleanly. Look at the bedroom, the fingerprints in many places have been wiped clean. Again In addition, the victim bled so much, the murderer must have spent a lot of time in the bathroom, rinsing rags, or even taking a shower and washing clothes. The probability of DNA being mentioned in the bathroom is very high."

"Xiao Hu and the others also guessed the same, and they all checked it carefully." Wang Zhong said.

"It's still too rough." When Jiang Yuan dealt with the corpse, he had paid attention to the operations of Xiao Hu and others, and there was nothing taboo about it at this time.

"Oh... Okay, I'll work overtime with you today." Wang Zhong didn't think so before, but now he began to realize that the level of several spot investigators in the team was indeed a bit casual, as if they were doing their own fingerprints. The technology is the same, and the best evaluation is probably "it works."

In the past few hours, although the missing fingerprints found by Jiang Yuan may not solve the case, they have proved that he and Lao Yan are not "usable" enough.

"Well..." The old man at the door couldn't stand still and said, "We have to go home for dinner."

"Sign and go back." Wang Zhong actually didn't expect the old man to stay long. Witnesses are all like this: they are either unwilling to get involved, wander around and talk nonsense, or are impatient.

Wang Zhong had no idea of ​​educating others, so he directly took the on-site inspection record, turned to the signature page, asked the two of them to write their names, then opened the door and let them out, only saying: "What you saw and heard today, You can only tell it when asked by the court or relevant departments, and you cannot leak it out, otherwise you will be criminally liable."

The two old men went out and nodded impatiently and said, "I know, I know."

Wang Zhong nodded as usual, closed the door and went back to the house, continuing to help Jiang Yuan wipe his DNA and fingerprints.

The lighting in the bathroom is not good, making it more difficult to clean.

Jiang Yuan wiped very vigorously.

Crime Scene Investigation LV4 not only improves his operational ability, but also his cognitive level.

Various crime theories actually explain the same truth. The longer the criminal stays at the crime scene, the more things he does, and the more flaws he exposes.

For example, the murderer this time seemed to have carefully cleaned up the crime scene and even took a bath calmly. But as far as Jiang Yuan understood, this just reflected the murderer's amateurism and arrogance.

Today's DNA technology can even identify identity information from sweat. It is absolutely impossible to clean the bathroom flawlessly in a short period of time. If it were a little more professional, they should at least wrap the bathroom with plastic. When the time comes, just take away the plastic and bury or incinerate it, so that much less physical evidence information will be leaked.

However, in that case, there will be traces of tape or sticky on the scene...

Jiang Yuan was actually not sure where the murderer's DNA could be found. He is young, has good physical strength, and rubs hard.

wipe.

Scratch...

Jiang Yuan is still in the excitement stage of a newbie. He has just obtained the crime scene investigation LV4 skill, and the only scene he has ever really investigated is this one. Naturally, try and practice as much as you want.

Among the skills of current survey, technique is of course very important, and meticulousness is indispensable. On the other hand, physical strength, concentration and other abilities are the key to reaching a higher level. This is like Xue Huaiyi falling out of favor with Wu Zetian. Is it because he has gained more experience and improved his skills, so he is disliked instead? Obviously not. In the same way, the Zhang brothers will not fall out of favor because they are young, reckless, and impulsive.

Wang Zhong lacked more than one or two of the above. However, although he was a little tired, he was led by Jiang Yuan and tried his best to support him.

Jiang Yuan wiped the ceiling and corners of the bathroom carefully.

The further he goes, the more careful and confident he becomes.

This house does not have dry and wet separation, but the bathroom area is small. When taking a shower, the probability of water splashing on the walls and ceiling is not low, and it is impossible to clean it thoroughly in a short time. The only problem is whether DNA can be wiped out. The blood stains were probably washed away or destroyed, but if you want to wash away all traces of DNA, this person is probably an amateur.

Ordinary people who commit unplanned killings will not learn relevant skills in advance. Even if you study, you don’t necessarily have to work hard and study hard, and you don’t necessarily have to be proficient in the study, so it stands to reason that there is a high probability that the police will catch you if you work hard, study hard, and be proficient.

At night.

Jiang Yuan and Wang Zhong dragged their bags back to the police station and went straight to the DNA laboratory.

Nowadays, there are more and more cases where DNA is used to directly solve crimes, and the police department’s investment in DNA laboratories is also increasing. Even Ningtai, a poor county, built a DNA laboratory under the guidance of various subsidies and policies and in accordance with the standards set by the ministry.

This is also the gold-eating beast unit of the police station. A total of three people work in the laboratory, which consumes more than 10% of the police station's funds every year, and it increases from time to time.

However, contrary to Wang Zhong's expectations, the DNA laboratory just silently accepted the piles of evidence bags and did not raise any objection.

They didn't even carefully check and criticize the biological test materials sent by Jiang Yuan and Wang Zhong.

"How come the old man from DNA has become so easy to talk to?" Wang Zhong followed Jiang Yuan directly to the forensic office and began to mutter.

In the forensic office, Wu Jun did not go home. Like most of the criminal police, he sat in the office and sorted out the information he had done during the day. Standing up and rubbing his eyes, Wu Jun said slowly: "In the afternoon, the team leader was still angry. The problem now is that there are no clues. The DNA laboratory hopes that you will send the test materials to avoid doing nothing."

Jiang Yuan listened happily: "Does it mean you have nothing to do if you don't work at night?"

"The captain didn't even go home." Wu Jun said: "If nothing can be found, they will have to conduct a re-examination themselves."

Wang Zhong looked at Jiang Yuan, tsked twice, and said: "It's in vain if they go. As far as their current investigation level is concerned, I don't mean to say that ordinary cases can be ignored..."

Wu Jun interrupted Wang Zhong: "Do you think they don't know?"

"Uh..." Wang Zhong was speechless and returned to his office silently.

Jiang Yuan was quite satisfied, so he packed up and rolled out the camp bed in the office.

Until the noise, the policemen who had stayed up all night started to quarrel.

"The DNA comparison matched a person, and Captain Liu took him there." Wang Zhong was the first to rush into the office, with secretions still hanging from the corners of his eyes.