There are a total of five people in the serious crime team, all of whom are elites in various fields, and this Jiang Tingbai is an expert in trace detection.

On the roof of the sixth floor of the crime scene, we found a broken and fallen wall, which was also a direct cause of the tragedy.

After Jiang Tingbai received our call, he quickly rushed to the rooftop of the crime with the technical team. Now we need to determine whether this case was an accident or homicide, and whether the shattering and falling of the wall was natural or man-made.

The police need evidence to handle the case, and even if everyone is sure of something, it needs to be supported by sufficient evidence. For the case to be closed, it is also necessary to close the chain of evidence.

The technical team immediately launched an on-site investigation, conducting a careful carpet survey of the entire rooftop, focusing on the fingerprints, footprints and biological samples left behind.

Jiang Tingbai put on the white gloves of the survey site and squatted in front of the gap in the entire fence to observe carefully.

"What does it smell like?" Jiang Tingbai suddenly frowned and said strangely.

"Do you smell it?" I also crouched down beside him and asked suspiciously.

Because we didn't smell anything on the rooftop, it was very windy, and even if there was a smell, it would evaporate quickly.

Jiang Tingbai moved a few more steps towards the gap in the wall, he was now squatting at the edge of this gap, and if he took another step, he would fall.

"Old dog, be careful." Li Meng felt a little frightened and said softly.

Jiang Tingbai didn't care, and reached out to wipe the edge of the gap in the wall, and the wall skin at the gap fell off some wall bricks like tofu slag.

"Did you find anything?" I lowered my voice and asked him lightly. For fear of a sudden sound, he would fall from the stairs.

But even if he falls, he will be fine, he is so fat, maybe he will bounce up and throw a few mimeographs.

"Why is this wall so crispy?" Jiang Tingbai looked at the powdered bricks on the fingertips of his gloves and muttered.

"Crisp? Could it be a state of disrepair? I asked, dumbfounded.

Jiang Tingbai shook his head, feeling a little strange, turned around and asked us, "If it were you, what would you do if you wanted to destroy the wall?" ”

Li Mengmeng didn't think about it, and said directly: "First use a small hammer to cut the seams, and then use a sledgehammer to do it, one hammer eighty." ”

Xue Hang stood behind him and said lightly: "I will use C4 to directly do a directional blasting." ”

Jiang Tingbai pondered for a while, shook his head again, and said, "The sound made by these two methods is too loud, and it is easy to expose yourself. Since the murderer has chosen this method of killing people disguised as accidental, he must ensure that he will not leave a trace. ”

"Silent cutting?" I asked suddenly.

Jiang Tingbai still shook his head and said to me: "This silent cutting method will only be used on construction sites, and it requires professional cutting tools, how could the murderer move large cutting tools upstairs?" ”

"Oh, don't sell the old dog, you must have the answer in your heart, so you can say it quickly. Do you want us to praise you again, and then you reply with a few words of 'low-key and low-key'? Li Meng said a little anxiously.

Jiang Tingbai smiled slightly, but to our surprise, he didn't have an accurate answer in his heart, everything was his guess.

I saw him put the brick foam stuck to his fingertips under his nose and sniffed it, and said slowly: "This brick foam has a pungent smell." ”

"That's what you just said it tasted like?" I frowned for a moment, because we really didn't smell anything.

Jiang Tingbai listened to me, and then handed the fingertips sticking to the brick foam under my nose and let me smell it.

I smelled it for a long time, but it was only the earthy smell of brick foam, not the pungent smell he said.

"Do you smell it?" Jiang Tingbai looked at me seriously and asked softly.

I shook my head dumbly.

Jiang Tingbai stood up and handed the brick foam on his fingertips to Li Meng and Xue Hang to smell it, but both of them said that they only smelled the earthy smell of the brick foam.

Jiang Tingbai believed in his nose as much as we believed in him.

He crouched down again in the gap in the wall, and gently scraped off some of the broken brick powder with his knife, which he wanted to collect, but the knife could not cut through the hard concrete wall.

He collected all the broken brick powder he had removed into an exhibit bag, ready to take it back for examination.

"So, what's the smell you're smelling?" I couldn't help but ask him.

Jiang Tingbai was not sure, and said with some hesitation: "It should be a chemical agent, and it is a chemical agent with extremely corrosive properties." The murderer used chemicals to corrode the cement wall, making it dry and crispy, thus completing the crime. ”

"No wonder only the gap in this wall is relatively dry around it, the other walls are very solid, and the entire concrete wall that fell from the sixth floor to the downstairs did not break." Li Meng sighed with some sudden realization.

"That's right, generally speaking, chemicals with strong corrosiveness have a strong pungent odor, and they are colorless and highly volatile." Jiang Tingbai explained.

"So what do you think is this extremely corrosive chemical?" Xue Hang asked him.

Jiang Tingbai thought for a while and said, "Strong acids, strong alkalis and other substances can quickly corrode cement. For example, sulfuric acid and hydrochloric acid, hydrochloric acid will have a chemical reaction with Ca(OH)2 in cement, and the resulting compounds will either be dissolved in water or expand in volume, resulting in cement damage. Others, such as sulfate (sodium sulfate, potassium sulfate), when sulfate penetrates into the cement stone structure, it will react with the calcium hydroxide in the cement stone to form gypsum, and the gypsum reacts with the calcium aluminate hydrate in the cement to form calcium vanadium stone to produce 1.5 times the volume expansion, which will inevitably lead to the cracking and collapse of the cement stone structure. In addition, there are strong alkalis, magnesium salts, alcohol, sugar, etc., which will have a corrosive effect on cement stone. ”

He said a lot, I didn't understand the specific content anyway, but I just knew that the cement wall was corroded by extremely corrosive chemicals, which caused the wall to break and fall off.

"I didn't expect you to be a chemistry expert!" Li Meng let out a heartfelt compliment.

Jiang Tingbai smiled greasy and said the most familiar line: "Low-key!" Low-key and low-key! ”

"You have to believe in the knowledge of a trace expert, a professional trace expert, or a physicist or a chemist." Jiang Tingbai said proudly.

He then put the evidence bag in his toolbox and prepared to take it back to test the ingredients, and although the chemical was very volatile, it could still be detected.

After a while, the technicians made a major discovery - the footprints of the murderer!