Chapter 297 The little things
The matter of reconstructing the scene can actually be understood as, let me imagine a crime.
To put it simply, it means where I enter the scene, whether it is from the door or the roof, whether it is from the window or the floor, or, like a medieval assassin, I make a retrograde attack from the bottom of the aqua toilet.
The way to enter the scene can also be imagined, and the actions within the scene can also be simulated, as well as the way and location of leaving the scene.
If there is enough blood for bloodstain analysis, Jiang Yuan can reconstruct the scene very beautifully, because the blood can simultaneously show the position, speed, and acceleration of the murderer and the victim.
To be honest, the skill of blood stain analysis is sometimes better than installing several detectors on the murderer. It is even more specific and real than what is captured by the camera.
Of course, this is the best situation.
General criminal investigators can only complete two ends. The middle part of the murder, especially the specific actions and steps of the murder, basically does not involve too much. That part can be completed by the forensic doctor. Well, in the end it belongs to Jiang Yuan.
As for the scene this time, there was not much blood and there were actually very few clues given.
But for Jiang Yuan, the only blood stains also revealed a lot of problems, such as the murderer's movement. He most likely came in through the door, and after two or three steps, he started to accelerate and knocked down the cashier with one blow. , and then swipe again.
Judging from these two decisive actions, the murderer is very decisive. He probably knows that there is money here, and may even have planned it for a long time. Jiang Yuan looked in the direction where the blood spattered and saw that the murderer should be carrying a murder weapon. He collected the money and continued to move forward...
Ahead is where the window is.
Jiang Yuan stood still, tilted his head and asked He Guohua: "How did you judge the murderer's movement, where did he come from, and where was he going?" He Guohua was already feeling a little lonely waiting, but now he heard the question was so basic, Jiang Yuan thought it was a casual question and said, "Come in through the gate here, beat the cashier to death, pretend to take the money, and then run out?
"His tone was uncertain. That was the case. There were not many signs in the room indicating the murderer's movements.
Whether it is crime scene investigation capabilities or blood stain analysis capabilities, there is an obvious gap between everyone.
Jiang Yuan didn't hold back and said directly: "The murderer jumped from the window."
"Ah" He Guohua was stunned for a moment, took two steps forward, suddenly stopped, turned around, and went to the door to bring several small transparent acrylic stools over. He placed a few on the window seat before standing at the window to look. under.
"Is this footprint where the murderer landed?" He Guohua was a little surprised.
The problem now is not that there are no footprints, but that there are too many footprints to identify. If it can be determined which footprints belong to the murderer, it will be a big breakthrough.
Wang Bo, a former high-latitude creature, was not overshadowed by Master's surprise. He asked with the spirit of independent thinking: "Master, the first thing to determine is not the murderer's movement line. Why did the murderer jump from the window?" .”
"Master Jiang already said that he jumped from the window." He Guohua glared at his apprentice, then looked over and said, "Look at the footprints below, do they look like the footprints of someone who jumped? Would a normal person jump from the second floor? ?" Someone might jump out of the window on the first floor...
The windows on the first floor are welded with steel bars, so you should pay attention to them. What do you see with your eyes?
"He Guohua turned around and scolded his apprentice.
Xiaobo originally wanted to question Jiang Yuan, but his business strength had not yet been trained, and he was hit by dimensionality reduction here in He Guohua. Wang Bo wanted to struggle, and then said: "The medical examiner Jiang didn't look downstairs just now...
"Doesn't that further prove that Mr. Jiang is awesome?" He Guohua was completely on the Internet, looking at Wang Bo as he looked at the enemy keyboard player.
Wang Bo shrank his neck and just muttered: "No one noticed if he didn't take the easy way out, why didn't he go through the door?"
This is where the difficulty lies. He Guohua looked directly at Jiang Yuan. Jiang Yuan spread his hands and said: "I can't tell for the time being, but based on the analysis of the traces at the scene, the murderer did this.
In fact, if you want to guess,
There can be many reasons. For example, the murderer is a parkour player, and he will walk in places like this instead of walking on good roads; or the murderer gets excited and jumps directly; or the murderer wants to use this method to confuse the investigation; or there may be more than one murderer , and someone temporarily decided to take advantage of others...
Jiang Yuan has no evidence to reason about this yet, and he doesn't want to speculate about it yet.
His goal is to solve the case, not to convince a young man like Wang Bo. If the latter is too troublesome, he can just replace him. He Guohua was much more obedient, and immediately followed Jiang Yuan's train of thought, saying: "In this way, the murderer can first be assumed to be a young man. Generally speaking, people in their thirties and forties will be more relaxed. I probably wouldn't choose to jump out of the window.
"The age is about thirty years old." Jiang Yuan also walked to the window, looked at the footprints on the ground from top to bottom, made a judgment, and said: "First collect the footprints below, and then go up to find the corresponding ones. of."
The footprints downstairs were caused by jumping down, and the marks are quite clear. Correspondingly, although the footprints upstairs are not visible, as long as they are collected, there will still be marks, but it may require the cooperation of some instruments.
Thinking of Jiang Yuan's ability to identify footprints, He Guohua's fire of hope was already burning brightly, so he picked up the survey box and left.
The sooner the footprints are collected, the better, especially outdoor footprints, which may be wiped out by a wind or a rain.
Nowadays, murder cases are relatively easy to solve. In fact, there is a reason. Murderers generally like to commit crimes indoors. Statistically speaking, the most common places to commit crimes are in their own homes.
This creates a situation where traces of crime are particularly difficult to remove. Like blood stains, the blood stains left in the room may still be there ten years later. Wherever it looks like in the wild, it only takes a few months or a few weeks to basically eliminate them all.
Of course, there are too many cameras outside, which is the main reason why everyone makes this choice.
Changyang City has an electrostatic adsorption instrument that is professionally used for footprint extraction. It is actually a palm-sized instrument with a few knobs on it, which can be adjusted slightly. He Guohua went downstairs and took a few photos of the footprints. Then he took out the electrostatic adsorption device, put it aside, and then took out a piece of insulating paper and covered it with the footprints.
The insulating paper is black and somewhat similar to old-fashioned carbon paper.
It itself is full of static electricity, shaking unruly.
After placing the insulating paper, He Guohua attached the two corners of the electrostatic adsorption device to the insulating paper, grounded one leg, and turned on the switch of the electrostatic adsorption device. The insulating paper immediately stuck to the ground.
"Roller." He Guohua stretched out his hand, and the young apprentice next to him immediately handed it to him.
He Guohua held the roller, pushed it gently on the insulating paper a few times, and explained to his apprentice: "Just push it flat. Don't use too much force. You will need to use glue later."
"oh."
Wang Bo nodded.
He Guohua handed the roller back to his apprentice, then gently peeled off the insulating paper. Using the angle of the light, he took a look and saw that the footprints had been clearly copied on the insulating paper.
He Guohua put the insulating paper into the box and processed it when he returned to the laboratory.
Later, He Guohua took out the viscose again.
The adhesive is a piece of black adhesive paper, the size of a standard A4 paper. It looks like sticky mouse paper, and the surface is also pitch black.
The adhesive is even simpler to use. Cover it directly on the footprints, brush it with a roller, and press it twice with your hands to pull it up directly.
However, after the adhesive treatment, the footprints on the ground will be damaged, which is why the static electricity is done first and then the adhesive is done.
Returning to the crime scene upstairs, He Guohua then turned on the investigation light, adjusted the light source, and swept away the footprints on the ground.
Even if the footprints on the ground are invisible to the naked eye, they will be clearly visible when struck with a survey light.
Exploration lights all have variable light length. If you really can’t see, you can also adjust the wavelength, but generally speaking, white light is enough.
He Guohua continued to collect the footprints.
Looking up again, he saw Jiang Yuan looking at the window in a daze.
"Brother Jiang
, the scan is finished. "He Guohua reported.
"Well... did you scan the window frame? Did you get any fingerprints?" Jiang Yuan gestured with his hand.
The window frame is made of plastic, which makes it difficult to take fingerprints. He Guohua smiled and said: "I have taken fingerprints, but I don't know if there is a murderer."
"Then let's get it again." Jiang Yuan then asked for the survey box and started cleaning it.
He Guohua hesitated: "Do you think the murderer touched this window frame?"
"You can try to simulate it. Hold the murder weapon in one hand and jump out of the window. Can you avoid hitting the window frame? Jiang Yuan gestured. He Guohua also gestured and murmured to himself: "It's really..."
Wang Bo said softly: "I can stay two meters away from the window, jump hard, lift my feet off the ground, pass through the window, and then land on the ground..." Wang Bo not only dictated, but also moved his body, with his feet on the bridge It's dangling here and there, but it's not crooked.
He Guohua said helplessly to Jiang Yuan: "He majored in gymnastics. He is a national first-class athlete."
Jiang Yuan could only snort twice and said: "Is it so rolled... If it's at the national level, let him go get some toner for the printer."
"Well... ok. Can it be used to brush fingerprints?" He Guohua asked, but without waiting for an answer, he sent Wang Bo out.
In the blink of an eye, Wang Bo was seen running in the sun.
Jiang Yuan nodded and said: "This kind of plastic material is very difficult to remove fingerprints. You can use printer toner mixed with magnetic powder to remove fingerprints."
Jiang Yuan talked about some tips, and He Guohua quickly wrote them down. On-site exploration is a delicate work, and the real test is actually these small places.