Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

Yang Sen opened the investigation box and took out the pH test paper and water quality detector. "First, test the pH and composition of the sewage. Maybe we can find clues related to the preservation of the body or the murderer's disposal of the body." He dipped the test paper into the sewage, waited for a while, and compared the color card. "The pH value is 8.2, which is weakly alkaline. It may be the residue of detergent or other chemicals. Let's take a look at this." He operated the water quality detector, and the data on the screen kept jumping. "A trace amount of chloroform was detected. Although the concentration is very low, it is enough to explain the problem."

"Chloroform?" Yang Lin's eyes lit up. "That's a powerful anesthetic. Combined with the resistance wounds on the body, it is very likely that the murderer first used chloroform to knock the victim unconscious and then dismembered the body." He made a quick note in the investigation notebook, the tip of his pen making a rustling sound as it moved across the paper.

The two continued to search in the sewage, and Yang Sen's metal detector suddenly made a rapid beep. "It's working!" Yang Sen followed the sound and groped under a pile of debris. "It feels like a metal sheet." He carefully pulled it out of the water. It was a bloody saw blade with some tissue and hair still on the edge.

"The sawtooth shape is completely consistent with the previous incisions on the body. This is very likely part of the murder weapon." Yang Lin put the saw blade into the evidence bag and said, "Send it immediately for DNA testing and metal composition analysis to see if we can find more clues."

As the search deepened, they found several more body fragments in different locations, including some bones and internal organs. Yang Sen marked the locations of all the fragments on the three-dimensional map of the tablet computer, and the red marking points gradually formed an irregular distribution.

"Judging from the distribution of the fragments, the murderer must have dumped the bodies from multiple entrances above," Yang Sen analyzed. "And these locations are all within the construction area. The murderer may have used the construction as a cover to dump the bodies."

"But the problem is," Yang Lin sighed, "the construction team has been using high-pressure water guns to clear silt and mechanical excavation these days, and traditional trace evidence such as fingerprints and footprints has been almost completely destroyed. Even fiber evidence is difficult to find. The sewage and construction disturbance have severely damaged the scene."

Yang Sen called up the panoramic view of the construction site taken by the drone and zoomed in to show each sewer outlet. "But there is still a chance. We can start from the pattern of body disposal. These body parts are distributed in 8 different inspection wells, forming an area with a radius of about 30 meters. The murderer chose these locations to dispose of the bodies, which shows that he is familiar with the sewer structure here."

"That's right." Yang Lin nodded. "And based on the degree of freezing damage to the body parts, we can infer how and when the body was stored after dismemberment. Combined with the chloroform detected in the sewage and the material analysis of the saw blade, we can still piece together a lot of clues."

At this time, Wang Shuai's voice came from the intercom: "Yang Lin, Yang Sen, there is new news from the construction team. They remembered that a van marked 'Municipal Emergency Repair' entered the construction site last week. The driver showed his ID, but now it seems that it is likely forged."

"Vehicle characteristics! Ask about the vehicle characteristics quickly!" Yang Lin said anxiously.

"It was a silver-grey van, the license plate was obscured by the mud, and the construction team members don't remember the other details very clearly." Wang Shuai replied. "It was a silver-grey van, which might have been the murderer's vehicle for transporting the bodies." Yang Sen marked the location of the vehicle on the map, "Combining this information with the distribution of the body parts, we may be able to find the murderer's route."

Yang Lin looked at the investigation record book in his hand, which was densely filled with various data and analysis. "Although the clues at the scene have been severely damaged, as long as we carefully analyze the remaining physical evidence, starting from chemical traces, corpse disposal patterns, etc., we will definitely be able to tear off the murderer's disguise." His eyes were firm, flashing in the dim sewer.

Yang Sen put away the equipment and took a last look at the evidence bag floating in the sewage. "Let's go. We need to go back and conduct more detailed tests and analyses on these samples. We will definitely get to the bottom of this case."

The two men stepped on the sewage and slowly walked out of the sewer. Night had fallen, and the lights at the construction site were still on, illuminating the bag in their hands that contained the key evidence.

When Yang Lin and Yang Sen left the crime scene with relevant government affairs, Wang Shuai and Zhang Hui also started their investigation.

Wang Shuai zoomed in on the blurry screenshot of the silver-gray van to the maximum. The mottled mud on the license plate in the surveillance video seemed to have become a puzzle. He rubbed his sore eyes and turned to Zhang Hui and said, "The construction team said there are words 'Municipal Emergency Repair' on the body of the truck. There are at least 300 vehicles with this kind of paint in the city. We must check them one by one." The rain outside the window started to fall at some point. The raindrops hit the glass windows of the Criminal Investigation Detachment, mixing with the rustling sound of the two people flipping through the documents.

They first came to the Municipal Engineering Management Office. The archive room smelled pungently of mold. The administrator, Lao Zhou, wore reading glasses and flipped through the registration book with great effort: "Silver-gray emergency repair vehicles? Two were scrapped last month. The current 037 vehicles all have GPS positioning." He called up the system, and dense dots of light flashed on the electronic map. "But three days ago, the positioning signal of a vehicle was indeed cut off for twelve hours. The number was SZQ-, but it returned to normal the next day."

Zhang Hui immediately wrote down the number and scanned the photo of the vehicle: "The paint on the car body is consistent with the description of the construction team. Could it be this car?" Wang Shuai shook his head: "Don't jump to conclusions yet. Go to the parking lot to see the real car." The two rushed to the parking lot in the rain. Car No. 037 was parked in a corner. The body of the car was covered with mud spots, but the wear marks on the door handles were completely different from the vehicles in the surveillance. Wang Shuai squatted down and picked up the stones in the gap of the tire with tweezers: "The construction area is shale geology, and these are river beach pebbles. The vehicle has never been to the crime scene."

The interruption of clues did not discourage them. The two began to visit shops within three kilometers of the crime scene. At the door of a hardware store, the proprietress wiped the glass and recalled: "Silver-gray truck? There was indeed one parked in front of the store in the early morning three days ago. The driver got off and bought a roll of tape and a flashlight." She suddenly slapped her thigh: "Right! There is a blue reflective strip on the front of the car, and a piece is missing from the left corner!" This detail cheered up Wang Shuai and Zhang Hui. They immediately retrieved the video footage from 37 surveillance cameras along the way and compared them frame by frame.

In the surveillance camera at the seventh intersection, a silver-gray van flashed by. Zhang Hui excitedly zoomed in on the picture: "That's it! The shape of the gap in the blue reflective strip matches perfectly!" However, when they followed the route, they found that the vehicle turned into an old residential area. The surveillance cameras in the residential area had been in disrepair for a long time, and in the few pictures that were available, the van disappeared behind Building No. 3. (End of this chapter)