wavenovel Chapter 1232 1 Line
Chapter 1232 1 Line
Chapter 1232 A Thread of Connection
The Beijing Bureau’s Forensic Building has its own physical and chemical laboratory, which is a relatively luxurious configuration because Building No. 9 of the Ningtai County Bureau does not have one.
Jiang Yuan found a clean laboratory table and asked Mu Zhiyang and Wen Ming to help him clean it carefully with alcohol. Then he took out the two plastic ropes and observed them carefully bit by bit.
This is the most valuable clue found so far, except for the body. Even though so much garbage was turned over, and these two plastic ropes were found in the early stage of the garbage search, experienced criminal police must realize that clues are not distributed linearly.
Making full use of every clue you know is the most basic respect for criminal investigation. Whether you get a lot of clues and evidence in one go, or just a little clue by luck, making the best use of them is the only thing a criminal police can do and what they should do most.
"131 cm long. 3 cm wide."
"246 cm long, 3 cm wide."
Jiang Yuan photographed the two plastic ropes again and again, making sure that there were no details in their shapes that could be discussed. He then carefully untied the two ropes, first measuring the length and width, and then looking at them along the plastic ropes bit by bit.
The so-called plastic rope is actually a wide, flat plastic belt.
It is so thin that the rope is translucent. It is 3 cm wide, which is roughly equivalent to the width of two male fingers, slightly more than three fingers, not counting fat people.
In this mode, when people use the plastic rope, they actually automatically twist it into one rope.
In other words, the plastic rope is wrinkled in width before use.
In this way, subtle evidence can easily remain in the gaps where the plastic rope is folded.
Jiang Yuan therefore specially wiped the test bench clean, then let the camera continue to shine on the table, then unfolded the plastic rope little by little, and then took samples in sections.
The plastic rope had been buried in the garbage dump for who knows how many days, and some parts of it were obviously soaked by the leachate from the garbage dump. This high-concentration organic wastewater is destructive to organic evidence. No matter whether it is DNA or something else, it will be destroyed if it comes into contact with this leachate.
However, when the two plastic ropes are folded together and pressed with other garbage, some folds form a relatively closed environment.
Theoretically, if there is evidence, it is possible that it exists in these places.
Jiang Yuan checked along the untied end all the way to the knotted part. At this point, he carefully examined each section with a horseshoe mirror before taking samples.
This is where the evidence is most likely to be found.
In the past, Jiang Yuan would only do this step, and the rest would be left to the technicians in the physical and chemical laboratory.
Now that Jiang Yuan has mastered the physical and chemical analysis level 5, he naturally leaves it to himself to do.
However, technicians of any level are faced with multiple-choice questions when they arrive here.
Although modern technology is already very advanced, it can detect and analyze very small amounts of substances.
But when sampling, there is still a quantity. Most importantly, there is no machine that can accurately and finely process the sampled evidence. And some evidence processing is lossy and slightly lossy, that is, after one test, other items cannot be tested.
In view of this, in physical and chemical laboratories, non-destructive projects are generally done first, followed by minimally destructive and lossy projects.
Jiang Yuan had to take samples first to avoid the garbage leachate from contaminating the samples, but after doing this, he also asked Mu Zhiyang to draw the curtains and started working on the non-destructive project first.
First scan with a multi-band light source, switching between 365nm ultraviolet light, 450nm blue light, 535nm green light, and 850nm infrared to see if there is any fluorescent reaction.
Among them, ultraviolet light can find blood, various body fluids and residues of some drug plants, such as marijuana resin. Blue light can find fingerprints, glue, and some synthetic fibers. For example, 502 will emit bright white fluorescence, and polyester will emit bright 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 coatings, and can find some burnt substances.
In summary, if an individual buys a handheld multi-band light source, and pulls up the curtains to shine a light on his boyfriend or girlfriend when they come home every day, he or she may be able to discover his or her true face of smoking marijuana, playing SM, taking cocaine, and painting his or her whole body.
The two plastic strips in front of me are clean.
Of course, this does not prove that they are innocent, it just means that the first wave of macro-inspections were fruitless.
Jiang Yuan then drew aside the curtains and asked someone to take a high-resolution camera to take another photo of the entire section. Then, under a stereo microscope, he used a micromanipulator to pick out the visible particles in the folds and put them into sample tubes. This step was micro-damage.
The last step is PCR and elemental analysis, which are the DNA testing and component analysis that many people are familiar with.
After finishing the whole process, it was already dark outside.
Wen Ming also snored softly.
Maki Zhiyang was huddled in a corner, playing with his phone out of boredom.
The technicians in the physical and chemical laboratory had to accompany Jiang Yuan to prevent him from damaging the expensive scanning electron microscope and gas chromatograph-mass spectrometer.
"Let's wait for the result." Jiang Yuan stood up, patted Wen Ming, and said, "Let's go 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, "How is Director Liu doing?"
"I'm still looking. I found several similar plastic straps in the market, and I don't think they're that different. I have to first identify the manufacturer of the plastic straps before I can find distributors and buyers." Mu Zhiyang paused and gave his own conclusion: "It doesn't seem to be that easy to find either."
"Well, go back and have some sleep, and we'll talk about it tomorrow." Jiang Yuan didn't say much. Various physical and chemical tests took time, so he sat in the car and reviewed today's technical analysis, but he was not in a hurry to draw a conclusion.
The next day.
Jiang Yuan arrived at the Forensic Building early.
The backlog case task force and Cui Qishan's Fourth Brigade simply moved here, set up their equipment in the conference room of the Forensic Medicine Building, and started a discussion meeting.
Various reports from the physical and chemical laboratories were also sent over.
The laboratory technicians worked overtime all night and finally completed most of the report that Jiang Yuan wanted.
Jiang Yuan looked at the pictures one by one, and the others also passed them around and looked at them one by one.
At this time, the conclusion of a sample caught Jiang Yuan's attention.
"Acrylamide and benzoic acid." Jiang Yuan reported after shaking his head twice, and asked, "What contains these two substances?"
"The most common places for benzoic acid are food and medicine, coatings, plasticizers, and other industrial fields." Wang Chuanxing is a bookish person, so he spoke out without hesitation.
"What about acrylamide?" Liu Jinghui asked.
"It's also found in cosmetics and chemical raw materials, and in food... I remember it's carcinogenic." Wang Chuanxing started ordering PADs.
Jiang Yuan then said: "Maillard reaction. All high-temperature fried foods contain acrylamide, including fried steak, fried dough sticks, fried chicken, and fried tempura."
"The murderer is the chef?" Liu Jinghui reacted instantly and added, "There shouldn't be any benzoic acid in normal cooking. Is benzoic acid in pre-prepared dishes?"
"It's also in various sauces." Wang Chuanxing had finished looking up the information at this time and said, "If it's considered food, it's in soy sauce, fruit juice, and various flavors. It's also a carcinogen."
"When are we going to catch this kind of person?" Liu Jinghui took a breath and frowned again: "Then ordinary people might also come into contact with it while cooking?"
Jiang Yuan shook his head: "It's all left in the plastic tape, which means it's a lot, not just a little bit... The victim rode a bicycle to Jinshan and listed all the businesses along the way. How many of them sell food?"
"Not many." Wang Chuanxing immediately looked for the list. These were sorted out a few days ago.
Soon, he pulled out a list of businesses along the route, and then pulled out the food businesses.
"Fried chicken, roujiamo, pancakes, fast food restaurants, convenience stores..." Liu Jinghui counted and found that there were dozens of stores in total, so he waved his hand and said, "Ask each one of them, and take notes from the chefs and store owners!"