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

Yang Sen walked over, holding a ruler and a camera: "Take photos to record this first, number it XC-01." The camera shutter clicked repeatedly, recording this area from different angles. "Place the ruler down and measure the length and width of the fluorescent area." Yang Lin placed the ruler next to the mark, "It's about 30 centimeters long and 15 centimeters wide, with an irregular shape."

The two continued to expand their search area. Five meters from the burial site, on a pile of broken bricks, Yang Sen's searchlight swept across a blue brick and he noticed several parallel scratches on its surface. "These scratches are fresh, and judging from the angle, they look like they were made by a sharp object dragging it." He examined them carefully with a magnifying glass. "The scratches are about 0.5 millimeters deep, with smooth edges, so they were probably made by a metal tool."

Yang Lin leaned closer: "Could it be related to the murder weapon? But there's no blood on the brick surface." He took out luminol reagent and sprayed it on the brick, but the expected blue fluorescence didn't appear. "Take a sample first, and take it back to analyze the composition of the scratches using a scanning electron microscope." Yang Sen took out an evidence bag, carefully put the brick inside, and labeled it.

At the edge of the excavation pit, Yang Lin found several blurry footprints. "These footprints were damaged too badly by the construction; only the general outlines are visible." He used plaster powder to fix the footprints in place. "The tread pattern on the soles is completely illegible, and the size and depth are inconsistent, so they must have been left by different people."

Yang Sen pulled up the 3D model and marked the footprint locations in the virtual scene: "Judging from the distribution of footprints, this is indeed an area with frequent footsteps, making it difficult to determine which ones are related to the case." He suddenly pointed to a corner of the model, "However, there is a small indentation in this location, which looks like it was left by a knee. Let's go take a look."

The two arrived at the marked location, and Yang Sen gently inserted a probe into the soil: "The soil has obvious layers. The upper layer is newly filled construction waste, and the lower layer is darker in color and has higher moisture content." He dug out a small handful of soil and put it in a sealed bag, "to take back and do soil composition analysis, and compare it with the soil on the deceased to see if there are any differences."

While searching through the nearby rubble, Yang Lin found a broken nylon rope, similar in material to the rope found on the deceased's ankle. "The rope had an uneven break, as if it had been torn forcefully," he said, picking it up with tweezers. "But this kind of rope is very common at demolition sites, so we can't directly conclude that it's related to the case."

“Do a fiber comparison and check the surface deposits.” Yang Sen said, then began scanning the rope with a multi-band light source. “Look, under blue light, there are fine white powders on the surface of the rope, which may be some kind of paint or lime.” He collected the powder. “This may be an important clue, but I’m afraid it may turn out to be just ordinary material left over from the demolition construction.”

Time ticked by, and the two men knelt on the ground, carefully examining every brick and every inch of soil. "The scene was so badly damaged. The bloodstains were washed away by the rain, and the footprints were covered by construction," Yang Lin said with some frustration. "Even the original position of the body was changed because of the excavation."

Yang Sen did not give up. He took a magnifying glass and continued to examine the soil around the body: "In this situation, we must not overlook any details. Look, there are signs of compression and deformation in the soil under the body. Although it has been turned over, we can still see the direction of the force." He used a twig to gesture on the soil. "The body should have been thrown down from above, not laid flat in the pit."

“But the angle and height at which the body was dumped are difficult to determine accurately now,” Yang Lin shook his head. “We’ll try to reconstruct it as much as possible, and then analyze it again when we get back, combining the 3D model and the autopsy report.” Yang Sen said, taking out a trace evidence extraction kit and collecting hair, fibers, and debris from around the body. As the afterglow of the setting sun shone on the demolition site, Yang Lin and Yang Sen finally completed their preliminary investigation. Their protective suits were covered in mud, and their faces were full of exhaustion. “Although we haven’t found any clear clues yet, these physical evidences might contain crucial evidence,” Yang Sen said, looking at the box full of evidence.

Yang Lin nodded: "Let's go. Now we'll see what the lab's analysis results are. Hopefully, the substances in the soil, fibers, and scratches will give us a breakthrough." The two carried their survey kits and walked out of the cordon under Lu Chuan's watchful gaze. In the red glow of the police lights, the demolition site remained silent, as if hiding countless secrets waiting to be uncovered.

Lu Chuan handed over the clues about Li Erzhu to Wang Shuai for investigation.

When Wang Shuai pinned Li Erzhu's photo to the whiteboard, the edges of the photo were wrinkled by the thumbtack. The 38-year-old demolition worker's eyes were evasive in his ID photo, and the scar above his right eyebrow gleamed eerily under the flash. "Focus on investigating his movements over the past month, especially before and after the incident," Wang Shuai instructed his gathered team members, his pen scribbling heavily across Li Erzhu's name.

The investigation began in the self-built house in the urban village where Li Erzhu rented. The narrow stairwell was piled with old cardboard boxes, and the smell of mildew mixed with cheap cigarette smoke hit the door. Wang Shuai knocked on the door of room 302, and the landlady opened it shakily: "Erzhu hasn't paid rent for half a month, and no one answers the door." The room was filled with a sour smell, instant noodle containers were piled up like a small mountain, and demolition team safety helmets and worn-out work gloves were scattered on the bedside table.

"Get the surveillance footage from the landlord." Wang Shuai squatted down and pulled out an iron box from under the bed. Inside were neatly stacked bundles of cash, with mud stains still clinging to the edges of the hundred-yuan bills. Technicians quickly began investigating the room and found an old cell phone in a hidden compartment of the wardrobe. After turning it on, dozens of encrypted messages popped up, all sent late at night, with messages like "See you at the usual place" and "The goods are ready."

Following the clues, Wang Shuai led a team to raid the scrap metal recycling station that Li Erzhu frequented. The owner turned pale the moment he saw the police, his phone still vibrating in his pocket. "He always brings in construction waste in the middle of the night, saying there are steel scraps inside." The owner trembled as he opened the surveillance footage. In the footage, Li Erzhu's tricycle had a welded-in double-layered cargo bed. When it drove into the recycling station at two in the morning, the cargo bed was noticeably lower than when it was empty.

More crucial evidence came from the demolition office's backup surveillance footage. Wang Shuai searched the archives for three days before finally finding deleted video clips on a hard drive in a corner. The recovered footage showed that a week before the incident, Li Erzhu, during his lunch break, stripped the outer sheath of copper wires in the demolition area and stuffed them into his tool bag. He was skilled, completing the theft in just five minutes, and even cautiously scanned his surroundings before leaving.

"Investigate his channels for selling stolen goods." Wang Shuai printed out screenshots from the video; every frame clearly showed the scars on Li Erzhu's face. Following the clues provided by the recycling station owner, the police arrested a gang of receivers of stolen goods at an underground scrap metal market on the outskirts of the city. In the interrogation room, the receivers of stolen goods shouted, covering their heads, "Li Erzhu always brought things from the demolition area—stealing steel bars, copper wire, aluminum alloy—anything valuable!" (End of Chapter)