The crackdown on organized crime began with the arrest of the mother-in-law.

Chapter 1140: The survey yielded too little information.

A pale blue fluorescence lit up in the murky air, like a twisted snake, spreading upwards about two meters along the cave wall. "Expand the investigation area to 50 meters upstream and downstream of the culvert entrance, and 20 meters on both sides of the roadbed," Li Ming's voice mingled with the distant sound of traffic. "Focus on checking for drag marks, suspicious footprints, and leftovers. Be sure to use an electrostatic precipitator to extract trace evidence."

Xiao Sun poured plaster powder into a portable mixing bucket, and milky white foam instantly appeared as the water and powder mixed. "I just extracted half of a size 42 shoe print," he said, using a scraper to evenly fill the depression in the silt with plaster paste. "Pressure surface analysis shows that the center of pressure on the forefoot is 1.2 cm outward, the stride width is 16 cm, the estimated height is 170 ± 2 cm, and the gait is a slight outward turn—consistent with the dragging direction in the culvert, so it should be left by the same person." He suddenly pointed to the air bubbles at the edge of the shoe print, "The silt contains fine sand particles, 0.3-0.5 mm in diameter, which may have come from the sand quarry upstream."

As the two searched along the drainage ditch upstream of the culvert, Xiao Yang's investigation light stopped beside a puddle. Deep blue fibers floating on the surface fluoresced bright blue under the ultraviolet light. He carefully picked them up with tweezers; the fibers displayed a three-strand helical structure in the beam. "Nylon 66 material, 20 denier monofilament," he quietly stated the parameters to the evidence bag, "consistent with the fiber composition of the deceased's jacket, but with a different twist—possibly from the murderer's clothing, washed here by the water." Xiao Sun was measuring the straight-line distance between the puddle and the culvert. "37.5 meters, water flow speed 0.2 m/s. Based on the fiber's floating speed, the separation time was approximately 3 hours, consistent with the timeframe of the crime."

In the bushes north of the roadbed, Xiao Sun's hiking boots kicked an irregularly shaped rock. Iron filings were embedded in the fresh scratches on the rock's surface. After spraying it with magnetic powder, clear tool marks appeared. "A curved blade, 3cm wide," he covered the marks with rubbing paper, "consistent with the characteristics of a claw hammer strike, and it's a new tool—the iron filings have low oxidation levels, and the time since formation was no more than 72 hours." Xiao Yang suddenly noticed a folded cigarette box next to the rock. "Hongtashan cigarettes, 11mg tar, the same brand as the cigarette butts found in the culvert, but this cigarette box has a tear and teeth marks on the edges, possibly bitten by the perpetrator in a moment of panic."

Expanding the search area to 50 meters, Xiao Yang discovered parallel scratches on the concrete wall of the drainage ditch. "The spacing is 15cm, and the depth is 0.2cm," he measured with calipers, noting that the forking angle at the end of the scratches was 30 degrees. "These were left by dragging a hard-edged object, and they match the width of the deceased's suitcase." Xiao Sun crouched down and used a soil sampler to extract soil from the area next to the scratches. "We sampled in layers up to a depth of 20cm. The top 5cm of soil was disturbed and contained a large amount of humus—indicating that it had been recently disturbed. The underlying loess layer was unaffected, and the disturbance occurred around the time of the incident."

“The footprint analysis has yielded new findings,” Xiao Yang pointed to a series of shallow marks along the edge of the roadbed. “The size 42 shoe prints showed an increased stride frequency and a shortened stride length from 70cm to 55cm as they approached the culvert, indicating a shift in the center of pressure forward.” He drew a gait curve in his notebook. “This suggests that the perpetrator was tense as they approached the body disposal site, consistent with the behavioral characteristics of ‘rushing to escape after committing the crime.’ Moreover, the outer forefoot of the shoe prints showed 8% more wear than the inner forefoot, consistent with the previously inferred ‘mild pigeon-toed’ gait, likely a gait habit resulting from long-term driving or cycling.”

In a patch of fallen wild rose bushes, Xiao Sun used a metal detector to scan for unusual signals. Pushing aside the thorny branches, he found a broken key, made of brass, with moderately worn teeth. "The key handle has engravings, but they've been worn down," he said. After wiping it with an alcohol swab, a faint "万" (wan) character appeared. "It might be a key for a suitcase of a certain brand. Let's compare it to the lock of a suitcase in the culvert." Xiao Yang suddenly noticed a dark brown hair hanging from a rose thorn. "It's 15cm long, relatively soft, and shows signs of perming and dyeing, which doesn't match the victim's black hair—it might belong to the murderer."

As the two searched upstream along the drainage ditch, Xiao Sun's ultraviolet light shone pale blue spots on the water's surface. "Occult blood reaction," he quickly covered the spots with an absorbent membrane, "distributed in dots, with density increasing from sparse to dense, reaching its highest concentration at the culvert entrance—indicating continuous bleeding during the dragging process, possibly from injuries sustained by the deceased or the perpetrator." The spots were droplet-shaped with serrated ends, "the drop height was about 1.2 meters, consistent with the characteristics of blood dripping from an adult walking, and the stride perfectly matched a size 42 shoe print."

“But there’s a contradiction,” Xiao Yang said, squatting beside the stone slab at the culvert entrance, tracing the worn edges with his fingers. “The slab weighs about 50 kg, and it would require at least two people working together or using a lever to fasten it from the outside,” he pointed to the gravel under the slab. “But we didn’t find any lever marks or other footprints around—could the murderer have done it alone?” Xiao Sun suddenly pointed to the scratches on the bottom of the slab. “There are rotation marks, 30 cm in diameter, indicating that a single person pushed the slab to rotate and fasten it. It would have required a lot of strength. The murderer was probably a young, strong male with good physical strength.”

In the weeds on the south side of the roadbed, they found partial remnants of tire tracks. "Biased tires, tread width 225mm," Xiao Sun explained, after filling the area with plaster, revealing a clear tread pattern. "Wear index 320, belonging to economy car tires, such as Jetta or Santana." He measured the wheel track, "145cm, consistent with compact car characteristics, and there's a 0.5cm cut in the tread, matching the scratch marks on the metal sheet near the culvert entrance—the murderer likely drove here to dispose of the body."

“All the clues are too fragmented,” Xiao Yang said, spreading his investigation notebook on the hood of the car. Sunlight filtered through the clouds, dancing on the words “Unidentified male, around 40 years old, 170cm tall.” “There’s no identification, no clear murder weapon. Fibers, footprints, and bloodstains all point to the killer, but there’s a lack of directly related physical evidence.” Xiao Sun’s phone received a preliminary report from the lab: “The dark blue fiber is nylon 66, commonly found in work jackets; the DNA from the cigarette butt matches that found in the culvert, but there’s no match in the database; there are traces of hair dye in the hair, and the pigment composition matches a certain brand of hair dye.”

As the two sat by the drainage ditch sorting through evidence, a gust of wind suddenly blew up a fallen leaf, which landed on the red rope marking the "prime suspect area." "The biggest suspicious point is the way the body was disposed of," Xiao Yang said, gazing into the depths of the culvert. "The fact that the murderer chose this spot to dump the body indicates familiarity with the surrounding environment—knowing it was remote and that recent maintenance work might have covered up the traces." Xiao Sun added, "But he left too many traces: shoe prints, bloodstains, fibers... His counter-surveillance awareness was inconsistent, unlike that of a repeat offender; it seemed more like a spur-of-the-moment decision."

After extending the investigation to two hours, the last piece of evidence was collected.