Chapter 1218: A Thread of Fate

In the forensic building of the Beijing Bureau, there is its own physical and chemical laboratory, which is a relatively luxurious configuration, because there is no such thing in Building 9 of the Ningtai County Bureau.

Jiang Yuan found a clean experimental table, and asked Mu Zhiyang and Wen Ming to help him clean it carefully with alcohol, and then 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. Don't look at turning over so much garbage, and finding these two plastic ropes in the early stage of turning over the garbage, experienced criminal police must realize that clues are not linearly distributed.

Making full use of every clue you know is the most basic awe for criminal investigation. Regardless of whether you get a large amount of clues and evidence in one breath, or get a little clue by luck, making full use of them is the only thing criminal police can do, and it is also the thing they should do most.

"Length 131 cm. Width 3 cm."

"Length 246 cm, width 3 cm."

Jiang Yuan took pictures of the two plastic ropes again and again, determined that there were no details for discussion in terms of form, and then carefully untied the two ropes, first measured the length and width, and then looked at them bit by bit along the plastic rope.

The so-called plastic rope is actually a wide and flat belt made of plastic.

Its thickness is extremely thin, making the rope in a semi-transparent state, width 3 cm, about equivalent to a man's two fingers slightly more, less than three fingers wide, fat people count separately.

In this mode, when people use plastic ropes, they actually automatically rub the plastic rope into a strip.

In other words, it is to use the plastic rope in the width, wrinkled.

In this way, fine evidence is easily retained in the gaps of the plastic rope folds.

Jiang Yuan therefore specifically wiped the test bench clean, let the camera continue to shine on the table, then unfolded the plastic rope bit by bit, and then sampled in sections.

The plastic rope was buried in the garbage dump for an unknown number of days. Some places were obviously soaked by the leachate of the garbage pile. This high-concentration organic wastewater is destructive to organic evidence. Whether it is DNA or anything else, it will be finished if it touches this leachate.

However, the two plastic ropes were folded and pressed with other garbage, and some folds formed a relatively closed environment.

Theoretically, if there is evidence, it is possible to exist in these places.

Jiang Yuan checked along the untied end to the knotted part. Here, every section was looked at carefully with a horseshoe mirror, and then sampled.

This place is the place where evidence is most likely to appear.

In the past, Jiang Yuan did this step, and the rest was handed over to the technicians in the physical and chemical laboratory.

Nowadays, Jiang Yuan already has LV5 physical and chemical analysis, so he naturally left it to himself to do.

However, technicians of any level come to this point, and what they face are multiple-choice questions.

Although modern technology is already very developed, it can perform detection and analysis on a very small amount of substances.

But when sampling, there is ultimately a quantity. Most importantly, there is no machine that can perform accurate and refined processing on the evidence sampled. And some evidence processing is destructive and micro-destructive, that is to say, a test is performed, and other items cannot be tested later.

In view of this, in the physical and chemical laboratory, non-destructive items are generally done first, and then micro-destructive and destructive items are done.

Jiang Yuan was to avoid the garbage seepage polluting the samples, so he had to sample first, but doing this step, he also greeted Mu Zhiyang to pull the curtains and started to do non-destructive items first.

First, scan with a multi-band light source, switch 365nm ultraviolet, 450nm blue light, 535nm green light, 850nm infrared respectively, to see if there is a fluorescence reaction.

Among them, ultraviolet can find blood, various body fluids and residues of some drug plants, such as cannabis 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 burns may also emit bright spots. Infrared can see some inks and coatings, and can find some charred substances.

In summary, if an individual buys a handheld multi-band light source and pulls the curtains for a pass when the boyfriend and girlfriend go home every day, they may discover the true face of him smoking marijuana, playing SM, inhaling cocaine and painting his whole body.

The two plastic strips in front of me are clean.

Of course, this cannot prove that they are innocent, it is just that the first wave of macro-inspection was fruitless.

Jiang Yuan then opened the curtains, first let people take pictures of the whole section with a high-resolution camera, and then under the stereomicroscope, picked visible particles in the folds with micro-operation, and then put them into sample tubes separately. This step is micro-destructive.

Finally, it is PCR and elemental analysis, which is the DNA detection and composition analysis that many people are familiar with.

After the whole set was done, it was dark again outside.

Wen Ming also made a slight snoring sound.

Mu Zhiyang huddled in the corner, playing with his mobile phone in boredom.

The technicians in the physical and chemical laboratory had to accompany Jiang Yuan, for fear that he would break the expensive scanning electron microscope and gas chromatography-mass spectrometry.

"Wait for the result." Jiang Yuan stood up, patted Wen Ming, and said: "Go back."

"Ah, is the case solved?" Wen Ming stood up suddenly, still a little confused.

Jiang Yuan shook his head, and then said to Mu Zhiyang: "How is Liu Chu's side?"

"Still checking, found a few similar plastic strips in the market, felt there was no big difference, have to determine the manufacturer of the plastic strip first, to find distributors and buyers." Mu Zhiyang paused, and gave his own conclusion: "It feels like it's not easy to find."

"Hmm, go back and sleep, talk about it tomorrow." Jiang Yuan didn't talk much, various physical and chemical inspections had to run time, he sat in the car, and then re-reviewed today's various technical analyses, but didn't rush to give a conclusion.

The next day.

Jiang Yuan came to the forensic building early.

The Cold Case Task Force and the Fourth Detachment of Cui Qishan simply moved over, set up a formation in the conference room of the forensic building, and started a discussion meeting.

Various reports from the physical and chemical laboratory were also sent over.

After a night of work, the technicians in the laboratory worked overtime and finally gave most of the reports Jiang Yuan wanted.

Jiang Yuan looked at them one by one, and others passed them on one by one.

At this time, the conclusion of a sample attracted Jiang Yuan's attention.

"Acrylamide and benzoic acid." Jiang Yuan shook the report twice and asked: "What contains these two things?"

"The most common places for benzoic acid are food and medicine, coatings, plasticizers, and then other industrial fields." Wang Chuanxing is a reading type, and said it out.

"What about acrylamide?" Liu Jinghui pursued.

"Cosmetics and chemical raw materials, food also has... I remember it is carcinogenic." Wang Chuanxing started to check the PAD.

Jiang Yuan said at this time: "Maillard reaction. All high-temperature fried foods have acrylamide, including fried steak, fried dough sticks, fried chicken, fried tempura, all have it."

"Is the killer a chef?" Liu Jinghui reacted instantly, and then added: "Normal cooking, there should be no benzoic acid, is benzoic acid in pre-made dishes?"

"Various sauces also have it." Wang Chuanxing finished checking the information at this time and said: "If you count food, soy sauce, fruit juice, various flavors all have it. It is also a carcinogen."

"When do we catch this kind of person." Liu Jinghui breathed a sigh of relief, and then frowned: "Then ordinary people cooking may also come into contact with it?"

Jiang Yuan shook his head: "It has been left on the plastic strip, indicating that the amount is very large, not the kind that is stained a little bit... The victim rode a bicycle to Jinshan, list all the merchants along the line, how many sell food?"

"Not many." Wang Chuanxing immediately pulled out a list. These were all organized a few days ago.

Soon, he pulled out a list of merchants along the line, and then pulled out food merchants.

"Fried chicken, meat sandwich, pancake fruit, fast food restaurant, convenience store..." Liu Jinghui counted, and found that there were only dozens of shops in total, so he waved his hand: "Ask them one by one, and the statements of chefs and shop owners must be done well!"

(End of chapter) ===== CHAPTER 1219 =====