civil forensic

Chapter 25
After wiping the cup, wipe the glass, after wiping the glass, wipe the mirror, after wiping the light, rub the rough one, after the thick one, wipe the thin one, after wiping the thin one, wipe the soft one, after wiping the soft one, wipe the hard one...

Survey work, from a large perspective, is of all kinds, but from a detailed perspective, it is all small and trivial matters.

The police say that the detection of the case is based on the accumulation of resources, which can be reflected during the investigation period.

Just like wiping DNA and fingerprints, laymen often think that as long as criminal suspects leave DNA or fingerprints at the scene, they 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
Like fingerprints, first of all, there are three types: dominant, plastic and recessive. The former two can be seen, while the latter, as the name suggests, requires certain means to see.And these methods also adopt different schemes according to the different materials of the location where the fingerprint is located.Or powder, or pipe, or smoke, or chemical, or different chemical, or different chemical...

In view of this, in order to obtain a fingerprint, the surveyor or trace inspection personnel first need to judge where there may be fingerprints, and then observe. The observation method can be carried out by naked eyes with the help of light or angle, or by breathing on a smooth surface. Observe with a magnifying glass or ultraviolet light.After the location of the fingerprint is determined, the fingerprint is extracted by brushing powder, or using iodine smoke or silver nitrate or other reagents for chemical extraction.

Therefore, if a spider-man really climbed over the ceiling, there is a high probability that the person doing the on-site survey will not find the fingerprints on the ceiling.

DNA is as much trouble as fingerprints.

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

It is common to extract DNA from the victim's toothbrush. Of course, the police who do the extraction can't see anything. They just guess that there is a high probability of DNA on the toothbrush.

Switching to items with less high probability, such as shirts, bed sheets and other underwear, or water glasses, porcelain bowls and other items, whether there is DNA on them is completely guesswork.

The ability to do field surveys is clearly reflected at this time.Some surveys think from the perspective of a criminal suspect, guessing the other party's actions, so as to find possible clues, and paint in an orderly manner; Pack it up, 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, and the more time and energy they invest, the higher the probability of finding clues and evidence.

In Wang Zhong's opinion, Jiang Yuan's operation method is very strong, but he thinks it is more appropriate during the murder case. If it is a theft case, it is almost impossible to operate like Jiang Yuan's.The cost of making a tube of DNA is 100 yuan less for reagents alone, and the number of times that can be done per unit time is even more limited.

"Let's clean the bathroom again." Jiang Yuan cleaned up the bedroom, and the sky was already dark.

Wang Zhongting patted his head, pointed to a large box of evidence bags, and said: "Why don't you come back tomorrow, there are hundreds of copies of these, and give them all to the laboratory, they will all go crazy."

Jiang Yuan explained: "There are more than half of them. It is estimated that no DNA can be mentioned, and no reagents will be used. The murderer made it too clean. Look in the bedroom, the fingerprints in many places have been wiped clean. Then In addition to the fact that the victim bleeds so much, the murderer must have spent a lot of time in the bathroom, washing rags, maybe 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 way, and they all checked carefully." Wang Zhong said.

"The rubbing is still too rough." When Jiang Yuan was dealing with the corpse, he had paid attention to the operations of Xiao Hu and others, so he didn't have anything to taboo at this time.

"Oh... well, I will accompany you to work overtime today." Wang Zhong didn't think so before, but now he also began to realize that the level of the few surveyors in the team is indeed a bit random, just like doing fingerprints by himself. Like technology, the best evaluation is probably "usable".

And in the past few hours, the missing fingerprints that Jiang Yuan found may not be able to solve the case, but it has proved that he and Lao Yan's "useability" is insufficient.

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

"Just sign and go back." Wang Zhong actually didn't expect the old man to stay for long.Witnesses are all like this, either they simply don't want to get involved, or they just walk around and talk, or they just have no patience.

Wang Zhong also had no intention of educating others, so he directly took the on-site inspection transcripts, turned to the signed page, asked the two to write their names, opened the door and let them out, only telling: "What you saw and heard today, It can only be said when asked by the court or relevant departments, and it cannot be leaked out at ordinary times, otherwise it will bear criminal responsibility."

When the two old men went out, they nodded impatiently and said, "I know."

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

The lighting in the bathroom is not good, and it is more difficult to wipe.

Jiang Yuan rubbed very vigorously.

Crime scene investigation LV4 not only improves his operational ability, but also his cognitive level.

And all kinds of crime theories actually explain a truth, the longer the criminal stays at the crime scene, the more things he does, the more flaws he reveals.

Like the murderer this time, he seemed to have cleaned up the crime scene carefully, and even took a bath for himself calmly, but as far as Jiang Yuan understood, this only showed the murderer's amateurism and arrogance.

The current DNA technology can even identify identity information from sweat. It is absolutely impossible to clean the bathroom to a flawless state in a short period of time.If it is really a little more professional, at least the toilet should be covered with plastic, and the plastic will be taken away, buried or incinerated, and the leaked physical evidence will be much less.

However, in that case, there will be marks of tape or sticky on the site...

In fact, Jiang Yuan is not sure where the murderer's DNA can be wiped.He is young, physically strong, and crazy.

wipe.

Wipe...

Jiang Yuan is still in the novice excitement period. He has just obtained the crime scene investigation LV4 skill, and the scene he has actually investigated is the one in front of him.Naturally, try and practice to your heart's content.

Among the currently surveyed skills, skills are of course very important, and meticulousness is essential. On the other hand, physical strength, energy and concentration are the keys to a higher level.It's as if Xue Huaiyi fell out of favor with Wu Zetian, because his experience and skills have improved, but is he disgusted instead?Obviously not.In the same way, the Zhang brothers will not fall out of favor because they are young and reckless and impulsive.

Of the above, what Wang Zhong lacked was not one or two. However, although he was a little tired, he was driven by Jiang Yuan and tried his best to support him.

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

As time went on, he became more careful and confident in his actions.

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 wall and ceiling is not low, and it is impossible to clean it thoroughly in a short time.The only problem is whether the DNA can be wiped.The bloodstains were probably washed away or destroyed, but this person is probably an amateur in washing away all traces of DNA.

Ordinary people, unplanned killings, normally don't learn related skills in advance.Even if you learn, you don't necessarily have to work hard, and you don't necessarily have to be proficient in learning, so there is a high probability of being picked up by the police who are hardworking, serious and proficient.

into the 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 investment of the police station in DNA laboratories is also increasing.Even Ningtai, a poor county, has built a DNA laboratory under the guidance of various subsidies and policies and in accordance with the standards given by the ministries and commissions.

This is also the gold-swallowing beast unit of the police station, a laboratory of three people in total, devouring more than 10% of the police station's funds every year, and it will increase from time to time.

However, unlike Wang Zhong's expectations, the DNA laboratory just silently accepted the piles of physical evidence bags and did not raise any objections.

They didn't even carefully examine and criticize the biological samples sent by Jiang Yuan and Wang Zhong.

"The old money from DNA, why has it become easier to talk about?" Wang Zhong followed Jiang Yuan directly to the forensic office, and began to mutter.

In the forensic office, Wu Jun didn't go home either. Like most criminal police officers, he sat in the office and sorted out the materials he had made during the day.Standing up and rubbing his eyes, Wu Jun said slowly: "In the afternoon, the team leader lost his temper. The problem now is that there is no clue. The DNA laboratory is eager for you to send over the test materials, so as not to be idle."

Jiang Yuan was delighted to hear it: "Does it count as having nothing to do if you don't work at night?"

"The captain didn't go home." Wu Jun said: "If they can't find anything, they will go to re-examine themselves."

Wang Zhong looked at Jiang Yuan, clicked his tongue twice, and said, "It's useless for them to go. As far as their current level of investigation is concerned, I'm not saying that ordinary cases are fine..."

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

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

Jiang Yuan was quite satisfied, he tidied up and spread out the camp bed in the office.

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

"One person was found in the DNA comparison, and Team Liu took him there." Wang Zhong was the first to rush into the office, with secretions still hanging from the corners of his eyes.

(End of this chapter)