In the stepped classroom, Lu Weiwei's performance is really eye-catching.

Everyone knows that Lu Weiwei, like Officer Wang, is from the criminal investigation team of the Furong Branch of Jiangnan City.

For forensic doctors, both of them are laymen, but instructor Zhang Hui's question did not make it difficult for the two.

This made many forensic doctors who wanted to see the joke quite disappointed.

Zhang Hui was stunned, and then he came to his senses from his surprised gaze: "It's very ...... Very good, please take a seat. ”

Lu Weiwei nodded, sat back, and winked at Gu Chen with her right eye.

However, there was a sudden whisper at the scene.

"The police of the Furong Branch of Jiangnan City are really powerful. ”

"Yes, two questions in a row, people blurted out, which shows that people's knowledge reserves are not as many as ordinary. ”

"Damn, are all the top students sent by Jiangnan City this time? No wonder they can come over to participate in the training. ”

......

It was also when he saw everyone bowing their heads and whispering, and the bald instructor Zhang Hui coughed twice, and the scene gradually quieted down.

"What the female student said just now is very good, yes, these characteristics make diatoms have a wide range of applications in red tide detection, aquaculture, water quality monitoring, resource investigation, paleoenvironmental analysis, oil exploration, forensic identification and other fields. ”

"And diatoms belong to the class of diatoms in the phylum of algae, a kind of phytoplankton, almost everywhere on the earth where water is retained, as small as a small puddle formed by the accumulation of rainwater, as large as the ocean that accounts for 71% of the earth's surface, diatoms can be seen. ”

"There are also diatoms, which grow as terrestrial types on the surface of moist soil, and on the exposed surface of other objects, and some of them float in the air. ”

Looking up at Gu Chen's direction, Zhang Hui found that Officer Wang and Lu Weiwei were high-five Gu Chen in celebration.

Suddenly, the flabby brow tightened again.

Zhang Hui coughed twice and said absent-mindedly: "We all know that there are more than 16,000 kinds of diatoms in the world, and the body length is generally 1-200 μm. ”

"Its most obvious feature is that the cell wall, except for a few species, is highly silicified, forming two transparent shells, upper and lower, which are sleeved together to form a siliceous cell wall, which is hard and stable, not easily destroyed, and not affected by decay and death. ”

"Even if concentrated sulfuric acid and concentrated nitric acid are boiled, it is difficult to destroy their texture characteristics, so based on these properties, diatoms play a significant role in forensic testing. ”

The PPT picture quickly turned the page and entered the next stage of blue-background copywriting.

Zhang Hui suddenly stood up, came to the whiteboard of the podium, and wrote some copywriting materials on the whiteboard.

Glancing back at everyone, Zhang Hui knocked on the whiteboard with the back of his hand and marked the key points.

"All pay attention, everyone remembers this, due to the active respiration of the person who entered the water before death, the diatoms can be inhaled into the alveoli with the drowning fluid, enter the blood circulation, and distribute to various tissues and organs. ”

"Moreover, through qualitative and quantitative analysis and comparison of diatoms in organ tissues and water, it is not only possible to directly determine the cause of death, but also to help infer the location of drowning. ”

When the forensic scientists heard this, they also copied it into the transcript.

Everyone may be aware of this, but many people are learning about the characteristics of diatoms for the first time.

Therefore, whether it is a forensic doctor who knows or does not know, everyone bows their heads and takes notes.

The style of painting on the scene is very harmonious, but only Gu Chen in the corner of the back row is still unmoved.

But it's not that Gu Chen is unwilling to take notes, it's just that because of this information, Gu Chen has already read it in the city library a few months ago.

What instructor Zhang Hui said just now, Gu Chen had already used his specialization-level memory to perfectly record in his mind.

The answer given by Officer Wang and Lu Weiwei just now is the best embodiment of their own verification of their memories.

Zhang Hui felt that Gu Chen was a little faceless.

From the beginning of the lecture to the present, Gu Chen has hardly moved his pen, which is a very alternative existence in the training system with serious dogma.

Zhang Hui frowned and continued: "Next, we have to talk about an old and difficult problem, that is, the identification of the cause of death of the corpse in the water. ”

Looking at Gu Chen's indifferent expression, Zhang Hui pouted and smiled: "I need a teaching assistant now to help me write a whiteboard, I don't know...... Which student would like to?"

The scene was quiet for a few seconds, and several students in the front row raised their right hands one after another.

However, after Zhang Hui pretended to observe, he suddenly pointed at Gu Chen and said, "Just ...... That student, yes, it's you, sitting in the back row, next to the female student who just answered the question. ”

"Me?" Gu Chen was suddenly named, and he also stood up directly to confirm.

"Yes, that's you. Instructor Zhang Hui confirmed again.

Only then did Gu Chen get out of his seat, and under the eyes of everyone, he walked down the stairs to the podium.

Zhang Hui handed the oil-based pen to Gu Chen, and said with a smile: "This student, you just stand here and help me write a whiteboard." ”

"No problem. Gu Chen nodded slightly, took the oil-based pen, and came directly to the whiteboard.

Zhang Hui breathed a sigh of relief, and said in his heart that this little comrade stood on the podium and listened to his lecture, so his attention should be able to concentrate, right?

It's also for his good to think about it......

So Zhang Hui sat back in his seat and continued to lecture.

"We just talked about a big problem, and that is the identification of the cause of death of a corpse in the water. ”

"Tuk Tuk Tuk ......"

As soon as Zhang Hui's words fell, Gu Chen had already written the six big characters "Identification of the cause of death of the corpse" on the top of the whiteboard.

Zhang Hui glanced at it and was quite satisfied, so he continued: "You must know that drowning is a way of death due to fluid blocking the airways and alveoli, hindering gas exchange, lack of oxygen in the body, and carbon dioxide retention, resulting in suffocation. ”

As soon as the words fell, Gu Chen had already listed several points, almost synchronously.

Zhang Hui didn't care, but continued: "According to the Global Drowning Report released by the World Health Organization in 2004, 342,000 people drown every year in the world, an average of 42 deaths per hour. ”

"According to statistics, about 60,000 people drown in China every year, and drowning is the third cause of accidental death in our country and the first cause of death in children under 14 years old. ”

After seeing that he finished speaking, Gu Chen suddenly stopped writing.

Zhang Hui glanced at him and reminded, "Write it down." ”

"Instructor, your data doesn't seem to be very accurate. Gu Chen didn't mean to continue, but questioned Zhang Hui.

The scene suddenly became lively......

Everyone didn't expect that Gu Chen would question the data of instructor Zhang Hui in person, in everyone's opinion, is Gu Chen too floating?

For a while, everyone in the audience was talking.

Seeing this, Zhang Hui also asked Gu Chen angrily: "This student, what is your name?"

"Gu Chen. Gu Chen said.

"Which unit are you from?" Zhang Hui asked again.

"The third criminal investigation group of the Furong Branch of Jiangnan City. Gu Chen said.

Zhang Hui suddenly snorted and said, "I said Gu Chen, I have read your file, you shouldn't be a forensic doctor, right?"

Gu Chen nodded.

"Then how do you question that my data is wrong?" Zhang Hui asked again.

Gu Chen did not speak, but changed the "Global Drowning Report" released by the World Health Organization in 2004 to 2014.

Subsequently, the figure of 342,000 drowning deaths per year was revised to 372,000.

Zhang Hui was suddenly stunned, he quickly looked down at the information in his hand, but he was suddenly startled.

There was nothing wrong with Gu Chen's revised data, but there was a data error in the information on his hand.

It is true that the statistical report is from 2014, but my own data is from 2004, a difference of 10 years.

In 2014, the number of drowning deaths was 372,000, but the data on hand was 342,000, a difference of 30,000.

Zhang Hui was suddenly a little surprised......

"How did this Gu Chen know? He could even know that my data was wrong? This is also incredible, right?"

Zhang Hui was frightened in his heart, but he picked up the information in his hand, and fingerprint assistant Yang Ting said: "Sample, you sorted out this information, right?"

"That's right. Yang Ting nodded silently: "It was sorted out according to your manuscript." ”

"Look at you, careless. Zhang Hui threw the A4 paper data on the table, and said angrily: "You made a mistake in these data." ”

"Hit ...... Big mistake?" Yang Ting heard this, and quickly checked herself: "No, right? Why is it a big mistake?"

Zhang Hui picked up the manuscript, tapped his fingers and said: "On the top of my manuscript, it is clearly written that according to the "Global Drowning Report" released by the World Health Organization in 2014, 372,000 people drown in the world every year, an average of 42 deaths per hour. ”

"And look at what you've done? 2014 became 2004, 372,000 people became 342,000 people, you were too careless. ”

"Really?" Yang Ting suddenly panicked.

She hurriedly took out the manuscript given to her by Zhang Hui from her document bag, and turned a few pages for verification.

After a while, Yang Ting was dumbfounded: "It's really a mistake." ”

Glancing at Zhang Hui, Yang Ting also bowed her head and apologized, saying, "I'm sorry, maybe I typed too fast and didn't verify it clearly, I'm really sorry." ”

"Okay, pay attention next time. Zhang Hui also waved his hand and asked Yang Ting to sit down first, and then said:

"Our work must be rigorous, this time it is just a report, and the next time there is a data error in the laboratory practice stage, it is not an ordinary seriousness, and it is very likely that the results of everyone's efforts will be in vain." ”

"Yes, yes, my pot. Yang Ting also had the courage to take the mistake, but she didn't understand it a little bit: "But...... How did Gu Chen know that my data was wrong? I haven't shown him this manuscript?"

"That's right, how did Gu Chen know?"

There are many people who have the same doubts as Yang Ting at the scene.

Can you know this kind of data?

Zhang Hui was also stunned, Yang Ting's question just now made him feel puzzled.

There was an error in his own data, and Gu Chen was able to find the problem in the first place.

More importantly, he was able to accurately express the real statistics, which shows that Gu Chen also knows something about this report.

Zhang Hui looked Gu Chen up and down, and then asked him, "Gu Chen, how did you know?"

"I've seen this Global Report on Drowning, which was published by WHO in 2014. Gu Chen said.

"Have you seen it?" Zhang Hui was skeptical and continued to ask him: "You have even been in contact with this?"

"A few months ago, I read it at our Jiangnan City Library. Gu Chen said.

Zhang Hui pinched his chin, and said in disbelief: "But...... It's been a few months, and you can even remember the data now?"

"Yes, but I remember that the WHO estimates that the actual number may be twice as high. ”

"Well said. Seeing that Gu Chen could accurately say these data, Zhang Hui's eyes changed when he looked at Gu Chen.

It feels like this young man has an excellent memory and is far better than the others.

After a period of embarrassment, Zhang Hui picked up the writing pen on the table, corrected the data, and then said:

"After all, due to the dense network of rivers and lakes in our country, the number of bodies that need to be identified every year is huge. ”

"Among them, the vast majority of the drowned bodies found in rivers, lakes and seas are accidental deaths of drowning people, but there are also some drowning people who commit suicide or homicide, and it is not excluded that the body is thrown into the water after death and faked as an accidental drowning case. ”

Zhang Hui glanced at Yang Ting, and Yang Ting immediately switched the slides.

At this moment, a picture of the city's river is displayed on the screen.

One side of the city's river is cordoned off by a police cordon, and next to the river is a makeshift blue tent set up by the police.

Zhang Hui coughed twice and continued: "Over the years, drowning deaths have occurred from time to time, but it is also very difficult to detect. ”

"It's okay to have witnesses and the cause of death can be determined, but for those who don't have witnesses to drowning, detection technology is needed. ”

"For fresh aquatic corpses, drowning can be identified by typical signs of drowning, such as mushroom-like foam in the mouth and nose, watery emphysema, and sediment in the respiratory tract. ”

"However, more than 80% of the bodies in the water were found to be highly decomposed, and the signs of drowning were gone. ”

In addition, the identification of the cause of death of the autopsy and histological examination has become a recognized problem in the world, and the cause of death is the key to the characterization of the case. ”

After a pause, Zhang Hui saw that Gu Chen had already written down the main points, and he couldn't help but say: "This involves the handling of the police." ”

"Because the cause of death is unknown, the case cannot be determined, which can easily lead to dissatisfaction among the family, as well as public opinion speculation and media hype. ”

"Therefore, our forensic doctors must accurately detect the cause of death of the deceased and give a satisfactory explanation to the family, otherwise it will cause big trouble. ”

Seeing Gu Chen's tacit understanding on the whiteboard, Zhang Hui's attitude was much better, and he casually asked Gu Chen, "Gu Chen, do you know any famous examples?"

Gu Chen stopped writing, and after thinking about it carefully, he said: "The 'Lan Keer incident' that occurred in the United States in February 2013 is a typical example. ”

"That's right. Zhang Hui nodded slightly, and said to the audience: "Therefore, if the investigation is not thorough, it will cause a lot of social problems, which requires our work to be rigorous, so this puts forward higher requirements for our forensic testing." ”

Glancing at Gu Chen, Zhang Hui said again: "Gu Chen, do you know what experiments our forensic scientists have done in order to solve the problem of identifying the cause of death of corpses in water?"

The scene was suddenly quiet, and they all sweated for Gu Chen.

The heart said that instructor Zhang Hui is relying on Gu Chen?

You can't pick one wool, right?

In fact, many forensic doctors in the audience also knew something, but Zhang Hui only gave Gu Chen the opportunity to answer, and also wanted to take the postgraduate examination to see the real level of this young man.

After Gu Chen's brief contemplation for a few seconds, the data flow in his brain began to tumble rapidly, and soon came to mind.

Gu Chen raised his head and said: "Forensic science workers have successively studied methods such as diatom testing, blood biochemical testing, foreign body element testing, plant pollen spore testing, and chlorophyll a testing. ”

However, except for diatom testing, other methods are limited to experimental research and have not been widely used in forensic practice. ”

"Well said. Zhang Hui was very satisfied with Gu Chen's answer, so he smiled and said, "So the diatom test, as I said, is the 'gold standard' for drowning diagnosis." ”

"There is controversy in the academic community about how to determine whether to enter the water before death or to throw the body into the water after death, but diatom testing has always been the most commonly used method in forensic practice. ”

"But there are also doubts and controversies. Gu Chen directly retorted back.

Zhang Hui frowned, a little unhappy, and said in his heart that this Gu Chen is here to smash the field, right?

But what Gu Chen said was right, Zhang Hui just wanted to speak, and another first-class police inspector sitting next to him said: "Gu Chen, you said that there are doubts and arguments about diatom testing, why?"

"Because at present, most forensic doctors at home and abroad use light microscopes to detect diatoms in the organs and tissues of drowning deceased people. ”

Although the method of diatom detection technology cannot directly determine the exact cause of death of the drowning victim, it has a positive effect on helping to determine the death location of the drowning death by comparing the type and quantity of water samples at the drowning location of the drowning victim. ”

Gu Chen seamlessly connected, expressed his opinion, and then said:

"Although diatom testing has been used in the diagnosis of drowning for more than 100 years, the value of diatom testing has been controversial, mainly because there are many diatom testing techniques and methods used by the forensic community in various countries around the world. ”

Speaking of this, Gu Chen directly picked up the oily pen and wrote on the whiteboard: "The main method is to extract and digest the sample, and then use the diatom enrichment method and the diatom observation method. ”

Looking back at the people in the audience, Gu Chen stepped forward directly and explained to everyone: "Since diatoms are widely distributed in nature, they are commonly found in fresh water, seawater, air and food, especially vegetables. ”

"In addition, the passive pollution of corpses in the water, atypical drowning and post-mortem entry into the water, and corpses that died in some water places lacking diatoms, as well as the pollution problem of the experiment itself, in fact, include many influencing factors such as containers and reagents, so that diatom testing has been controversial in diagnosing drowning. “

When everyone heard this, they also nodded frequently, as if what Gu Chen said made sense.

However, Gu Chen's old problem was committed again, and he instantly regarded this place as the scene of the crime, and involuntarily explained to everyone: "In fact, diatom testing laboratories at home and abroad have always used the technology of strong acid boiling and digestion, centrifugal enrichment, and light microscopic observation. ”

"These traditional technologies actually have significant shortcomings, in addition to the pollution problems mentioned above, which are also manifested in...... The recovery rate of diatoms extracted from organ samples was low, the test sensitivity was poor, and the false negative rate was high. ”

"However, diatoms are small in size, low in content, and limited by the magnification of the light microscope, which is prone to the problem of missed detection and false detection. ”

"Ahem. Seeing that Gu Chen had snatched his right to speak, instructor Zhang Hui complained a little, and quickly coughed twice as a reminder.

However, Gu Chen didn't pay attention at all, snapped his fingers and continued: "Diatom testing requires the species identification of the diatoms tested. ”

Forensic examiners often lack expertise in the taxonomy of diatoms and misjudge other foreign body attributes as diatoms, which to a certain extent restricts the application of diatom testing in the diagnosis of drowning. ”

"Good...... All right. Seeing that Gu Chen was talking endlessly and had no intention of stopping, instructor Zhang Hui was a little flustered, and quickly interrupted: "Gu Chen, you better sit back." ”

......