There is its own physical and chemical laboratory in the forensic building of the Beijing Bureau, which is a relatively luxurious configuration because there is no building 9 of Ningtai County Bureau.
Jiang Yuan found a clean laboratory table, asked Mu Zhiyang and Wen Ming to help him clean it carefully with alcohol, then took out the two plastic ropes and observed them carefully bit by bit.
This is the most valuable clue found at present, besides the corpse. Don’t look at the amount of garbage, and you found these two plastic ropes in the early stage of pursuing garbage. Experienced criminals must realize that the clues are not linearly distributed.
Making the most basic awe of criminal investigation as much as possible is to make use of every clue you know. Whether you get a lot of clues and evidence in one breath, or seeking Tianzhizhi got a little clue, making use of them as much as possible is the only thing the criminal police can do and the most important thing.
"Length 131 cm. Width 3 cm."
“Length 246 cm, width 3 cm.”
Jiang Yuan patted the two plastic ropes again and again, and confirmed that there were no details for discussion in terms of shape. He then carefully untied the two ropes, measured the length and width first, and then looked at them little by little along the plastic rope.
The so-called plastic rope is actually a wide and flat plastic strap.
Its thickness is extremely thin, making the rope translucent, with a width of 3 cm, which is about as many as two fingers for a man, and less than three fingers in width. Fatty calculates it separately.
In this mode, when people use plastic ropes, they actually automatically roll them into a single one.
In other words, it is used to wrinkle the plastic rope around the width.
In this way, subtle evidence is easily retained in the gaps in the folded plastic ropes.
Therefore, Jiang Yuan deliberately wiped the test bench clean, then let the camera continue to look at the table, then spread the plastic rope bit by bit, and then took samples in sections.
The plastic rope was buried in the garbage dump for a few days, and some places were obviously soaked in by the leachate from the garbage dump. This high-concentration organic wastewater is devastating to the organic evidence. Whether it is DNA or anything else, it will be done when it encounters this leachate.
However, two plastic ropes are folded and other garbage is pressed on, and some wrinkles form a relatively closed environment.
In theory, if there is evidence, it may exist in these places.
Jiang Yuan followed the untie end and checked until the knotted part. When he arrived here, he carefully looked at each section with a horseshoe mirror and then took samples.
This is where evidence is most likely to be produced.
In the past, when Jiang Yuan did this, the rest was left to the technicians in the physics and chemistry laboratory.
Nowadays, Jiang Yuan has physical and chemical analysis of LV5, so he naturally leaves it to himself.
However, when technicians of any level come here, they face multiple-choice questions.
Although modern technology has become very developed, it is possible to detect and analyze a small amount of substances.
But when sampling, there is still a quantity. The most important thing is that there is no machine that can accurately and finely process the sampled evidence. Some evidence is damaged and slightly damaged, that is, after a test is performed, other items cannot be tested.
In view of this, in physical and chemical laboratories, they usually do damage-free projects first, and then slightly damaged and damaged projects.
In order to avoid garbage oozing liquid contaminated the sample, Jiang Yuan had to take the sample first. However, to do this, he also asked Mu Zhiyang to pull the curtains and start with the lossless project.
First, use a multi-band light source to scan it, and switch between 365nm ultraviolet, 450nm blue light, 535nm green light, and 850nm infrared respectively to see if there is a fluorescence reaction.
Here, ultraviolet can find blood, various body fluids and some drug plants residues, such as cannabis resin. Blue light can find fingerprints, glue, and some synthetic fibers. For example, 502 will shine white fluorescence, and polyester will shine blue. Green light is mainly drug residues, such as cocaine will emit yellow-green fluorescence, and chemical burning may also produce bright spots. Infrared can see some inks and paints, and some burning substances can be found.
To sum up, if you buy a handheld multi-band light source, and every day when your boyfriend and girlfriend go home, you can pull up the curtains and just take a look, you may find out the true face of smoking marijuana, playing SM, sucking cocaine and coloring all over your body.
The two plastic tapes in front of me are clean.
Of course, this does not prove that they are innocent, but the first wave of macro inspections are fruitless.
Jiang Yuan then opened the curtains, first asked someone to use a high-resolution camera and then take the whole section. Then under a stereoscopic microscope, he used a micro-operation certificate to pick up the visible particles in the wrinkles, and then put them into the sample tubes separately. This step was slightly damaged.
Finally, PCR and elemental analysis, which is the DNA detection and component analysis that many people are familiar with.
After finishing the whole set, it was already dark outside.
Wen Ming also made a slight snoring.
Mu Zhiyang was nesting in the corner, playing with his cell phone bored.
The technician in the physical and chemical laboratory had to accompany Jiang Yuan so that he would not break the precious scanning electron microscope and gas chromatography mass spectrometer.
"Let's wait for the result." Jiang Yuan stood up, patted Wen Ming, and said, "I'm back."
"Ah, has the case been solved?" Wen Ming stood up suddenly, still a little confused.
Jiang Yuan shook his head and said to Mu Zhiyang again: "How is Liu Chu?"
"I'm still looking at it. I found a few similar plastic tapes in the market. I don't feel that there is much difference. I have to determine the manufacturer of the plastic tapes before I can find the dealer and buyer." Mu Zhiyang paused and gave his own conclusion: "It doesn't feel that it's easy to find."
"Well, go back and have a nap, and I'll talk about it tomorrow." Jiang Yuan didn't talk much. He had to run away all kinds of physical and chemical examinations. He got into the car and reviewed the various technical analysis today, but he was not in a hurry to give a conclusion.
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The next day.
Jiang Yuan came to the forensic building early.
The special case team and Cui Qishan's fourth brigade also moved over to the town, and set up a formation in the conference room of the forensic building and held a discussion meeting.
Various reports from the physical and chemical laboratory were also sent.
After a night of work, the technicians in the laboratory stayed up late to work overtime, and finally gave most of the reports Jiang Yuan asked for.
Jiang Yuan looked over one by one, and the others were also passing on them.
At this time, the conclusion of a sample attracted Jiang Yuan's attention.
"Acrylamide and benzoic acid." Jiang Yuan shook his lightly and asked: "What does it contain these two things?"
"The most common places in benzoic acid are food and medicines, coatings, plasticizers, and other industrial fields." Wang Chuanxing is a study-oriented person, so he said it.
"Where is acrylamide?" Liu Jinghui asked.
"Cosmetics and chemical raw materials, and food... I remember it is cancerous." Wang Chuanxing started to click on PAD.
Jiang Yuan said at this time: "Maillard reaction. All high-temperature fried foods have acrylamide, including fried steak, fried fried dough sticks, fried chicken, and fried tempura."
"The murderer is the chef?" Liu Jinghui reacted instantly and then added: "It should be no benzoic acid when cooking normally. Is benzoic acid from pre-made dishes?"
"It's also in all kinds of sauces." Wang Chuanxing finished checking the information at this time and said, "If you count food, it's in soy sauce, juice, and various flavors. It's also carcinogens."
"When will we catch such a person?" Liu Jinghui took a breath and frowned again: "That ordinary people may have come into contact with cooking?"
Jiang Yuan shook his head: "It's all left in the plastic belt, which means the amount is very large, not a little bit of it... The victim rode a bicycle to Jinshan and listed all the merchants along the route. How many food is sold?"
"There are not many companies." Wang Chuanxing immediately looked for a list. These were sorted out a few days ago.
Soon, he first pulled out a list of merchants along the route, and then pulled out the food merchants.
Chapter completed!