After listening to Jiang Yuan's words, the technical staff regained some motivation.
In the old scavenger's small courtyard, where he had just entered, several technicians gathered together and stood behind Jiang Yuan, listening to him while observing the blood stains on the ground.
Under the illumination of the headlights, the color of the blood was a little distorted, but the cruelty could still be vaguely felt.
The position of Jiang Yuan's finger was one of the few places on the ground that was not covered by objects in the hospital. Several blood spots were quite conspicuous.
"I don't seem to see any splatter-like blood stains here." Hou Xiaoyong also studied blood stain analysis, but he was not good at it and only knew some well-known knowledge.
Jiang Yuan only nodded lightly and said: "The book says that splattered blood often indicates the first scene, the starting point of the murder. But at today's scene, the murder weapon used by the murderer was obviously not lethal enough.
, this shows from another aspect that the murderer’s original purpose may not be to kill.”
Jiang Yuan compared it with his own head, and then said: "From the surrounding blood stains, it can be seen that the murderer should have used a blunt instrument. Moreover, you can see the speed of the blood stains. Look at this
It’s more obvious on the side wall.”
Everyone then gathered around to look at the blood stains on the wall.
On the wall made of red bricks mixed with cement, oval and long blood stains were the main ones, with some small blood stains in the front.
"This is the characteristic of relatively high-speed blood stains, indicating that the blunt weapon is not heavy and may be relatively long." Jiang Yuan also made analysis while watching.
Several technicians nodded, indicating that they knew these well-known knowledge.
"So, his first blow probably didn't bleed. There was no splatter-like blood stains." Jiang Yuan glanced at Hou Xiaoyong and answered his question.
Hou Xiaoyong couldn't help but nodded slowly after hearing this.
Indeed, if you hit your forehead with a blunt instrument, it will not bleed immediately.
"But after being beaten, Zhang Hong, the old scavenger who died, made an escape move. The blood on the fingerprints here was applied later. It can be seen that he ran forward." Jiang Yuan said.
Then he pointed forward and said: "There are fluttering blood stains here, indicating that the scalp was broken by the second blow."
Jiang Yuan took two more steps forward and saw a pile of collapsed objects in front of him.
"Here are the traces left by the seventh blow. Take a photo and bring up the blood evidence first. The rest can be put aside and picked up later." Jiang Yuan waved his hand in front of him to mark a section.
area.
Hou Xiaoyong and others, who were following Jiang Yuan to learn how to reconstruct the crime scene, were stunned and a little at a loss.
"You ask."
"You ask."
Several technicians glanced at each other.
The senior technician, tired of looking back and forth, got angry with his eyes and glared at everyone: "Are you going to ask or not? I won't care if you don't ask. What are you pretending to do at this time? When you are asked,
Get up, who of you will answer?"
Hou Xiaoyong sighed and asked: "Forensic Doctor Jiang, what does the seventh time mean?"
"Based on the order of strikes at the crime scene, I judged that this was what was left during the seventh strike." Jiang Yuan replied.
Hou Xiaoyong opened his eyes wide and said, "Didn't we just say that there was no bleeding in the first blow, but bleeding in the second blow, and then it should be the third blow."
"I guess the blood stains from the third blow are on the ground. You have to lift them up to see them now," Jiang Yuan replied.
This answer is actually understandable to everyone.
When the old man came in, the shelves were still in good condition and all the things were properly placed on the shelves. It was only with the attack of the perpetrator and the escape process of the victim that a large number of objects were moved from the temporary unstable shelves.
Fall down.
Therefore, anyone can figure out that the blood stains from the third blow were buried by the objects above.
The difference is, how did Jiang Yuan determine that the top one was the seventh blow?
Hou Xiaoyong held it in for a few seconds, but he still couldn't bear it anymore and asked: "Let's not talk about the blood stains from the third blow. Why do you say that the above was the seventh time, not the sixth time, not the third time?"
10 times?"
Jiang Yuan smiled warmly and said softly: "I counted it out. I have already completed the reconstruction of the crime scene in my mind, and then I told you."
Hou Xiaoyong was stunned immediately.
It was also because he stayed up late for too long that his judgment and IQ began to decline.
If he could sleep for 10 to 8 hours, he felt that he would be able to rebuild a few steps.
However, this is actually the misunderstanding given to bad students by all difficult problems.
Students who watch the teacher or other people's problem-solving steps and follow the problem-solving sequence step by step often have the misunderstanding that I have learned it.
In fact, students who read it step by step are still very far away from learning.
In fact, most math problems are not solved step by step. Instead, we first look at the needs at the end or the middle, and then look at how to meet the needs at the end and middle.
Just like the reconstruction of a crime scene, no expert in bloodstain analysis can really guess where the first step is and where the second step is. They can guess it step by step.
This is stupid and creates too much unnecessary burden on yourself.
Just like the first step, according to the information Hou Xiaoyong learned, it seems that he should look for splatter-like blood stains, but according to Jiang Yuan's judgment, the first blow did not produce blood. What should I do?
As for Jiang Yuan's second step, it is similar. If you want to find the second blow, do you have to look at and analyze the blood stains one by one? Then you have to rule out the possibility that other blood stains are the second blow.
It's too troublesome and unnecessary.
The correct approach is to first determine whether the blood stains are from the early, middle, or late stages, or whether they are before or after the landmark event.
Arranging the positions of the confirmed blood stains and slowly filling in the blanks with the remaining blood stains is a relatively simple step in solving the problem.
Not enough. This is like a crossword puzzle, which requires overall control. To a certain extent, if you cannot completely reconstruct the crime scene, you cannot build half of the crime scene.
Technicians such as Hou Xiaoyong have actually not received training in reconstructing crime scenes.
There are many ways for domestic criminal science and technology personnel to learn things. The most common but basic ones are school courses. These things are the foundation of the basics and may not be used in practice. But if you don’t learn them,
, the subsequent development potential is very low.
For example, bloodstain analysis will use some high school physics and chemistry knowledge, such as momentum, angular velocity and other things. High school students actually need to spend several months and hundreds of questions to understand.
If a criminal science technician does not master the corresponding knowledge and is improvising, it is unlikely that his level of understanding will be the same.
In addition to school learning methods, reading books and learning skills from teachers in the workplace are the two most common modes.
In addition, various training activities continuously organized by various units have gradually become the mainstream for the improvement of technical personnel.
Techniques like extracting DNA from sweat now sound simple and commonplace.
But this was also promoted with great efforts around 2008. Before that, not only technicians could not do it, but the equipment and chemicals in the DNA laboratory did not necessarily support it.
Reconstructing a crime scene, for example, is too high-end. The above routes are basically difficult to practice on your own except for a master to teach you.
So I often act in TV dramas because I think it’s awesome.
Bloodstain analysis in the primary form will be discussed during training. However, Hou Xiaoyong and others are not particularly easy to learn.
In general, when Jiang Yuan said that he had completed the reconstruction of the crime scene, several technicians fell into deep thought.
Most of them were thinking: How is he going to lie to us?
Jiang Yuan waved his hand and said: "Here at the back, take another layer."
Several technicians put on their gloves silently and took out another layer of objects.
"If it's not enough, then take another layer."
Everyone follow and get it.
The pressure placed on the technical geeks by the stacked objects is no more than three girlfriends looking for cashiers at the same time.
"This should be the mark of the third blow." Jiang Yuan himself also marked it in his notebook.
Several people looked over and didn't know why, but they could only believe Jiang Yuan.
If you divide 857 by 648 verbally, you can't calculate it. So when you hear other people's results, you can only listen to them.
"This is the location for later hitting."
"The location of bleeding is very important."
"From here on, the murderer enters a state of excitement."
Jiang Yuan intermittently described the crime scene. Different from acting, his most important job now is to collect evidence.
After probing like this, a tiny blood spot attracted Jiang Yuan's attention.
"Wait." Jiang Yuan stopped the technician who was about to step forward.
"What's wrong?"
"Look at the impact point and speed of this blood spot. It's not the same as other nearby blood spots." Jiang Yuan took a quick look and noticed this blood spot.
But at this moment, the other technicians were all staring blankly.
How is there any difference? They obviously look the same...
"The trajectory of all blood spots in the air is basically a parabola. If this blood spot comes from the deceased, it is likely to cut a smaller angle."
As Jiang Yuan spoke, he asked people to take several photos.
"Do you suspect this was brought on by the murderer?" Hou Xiaoyong understood the meaning.
"At least the blood was splashed on the murderer and then splashed out. But the most likely thing is that it was the murderer himself."
Jiang Yuan said that he took matters into his own hands and carefully took out the blood spots in front of him.
Hearing what he said, the other technicians made a stir and gathered together again to stare.
"The murderer was injured? How was he injured?" Hou Xiaoyong asked anxiously.
Jiang Yuan glanced at him and whispered: "During the crime, the deceased may have resisted, maybe something splashed and hit somewhere, maybe the murder weapon injured himself..."
Jiang Yuan had no intention of explaining. For him, one drop of blood was enough to decide many things, and there was no need to demand full blame.
Someone left blood stains at the scene of a violent crime. Whoever he is, he should come to the police station and explain the situation!
