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

Yang Sen opened the footprint analysis system and entered the on-site data: "Based on stride length and stride width, the suspect's height is between 165 and 170 centimeters and his weight is about 60 kilograms, which is consistent with the analysis results of the inward gait."

Under the old locust tree at the west end of the village, Yang Sen's metal detector suddenly beeped. He crouched down and brushed aside the fallen leaves, revealing a rusty lighter in the sunlight, the words "Fishing Port" engraved on the windproof cover. "A windproof lighter, with fresh wear marks on the edges," Yang Sen said, bringing a magnet close to the lighter, where fine iron filings adhered to the metal surface. "There's a layer of rust, indicating it's been exposed to air for no more than a month, but the scratches on the ignition point show it was recently used." Yang Sen tested the surrounding soil with pH paper: "The soil pH is 6.5, a slightly acidic environment. The lighter is 20 meters from the cellar, on the main footprint line, so it should have been dropped by the suspect."

The two continued towards the northwest ditch. Yang Lin suddenly stopped in a patch of withered yellow grass, his searchlight beam focusing on a clump of black ash. "Isolated ash in the non-combustion zone," he measured the ash with a ruler. "It's about 4 centimeters in diameter, irregularly shaped, and contains unburned tobacco particles, 0.2-0.4 millimeters in diameter, consistent with the composition of the Hongtashan brand cigarettes found in the cellar." Yang Sen used an anemometer to measure the ambient wind speed: "Northwest wind, level two. Based on the wind speed, this isolated ash must have fallen when the suspect stopped here, indicating that he briefly stayed here after committing the crime."

On the muddy ground beside the ditch, there was a fresh scratch mark, with grayish-white mud powder accumulated in the cracks between the stones. Yang Lin shone the scratch mark with a sidelight: "A unidirectional linear scratch mark, 15 centimeters long, 0.3 centimeters deep at the beginning and 0.1 centimeters shallow at the end, consistent with the characteristics of dragging a hard object." He took out a silicone mold and carefully covered the scratch mark: "Extracting three-dimensional traces, it may have been caused by a tool carried by the suspect—the shape of this scratch mark matches the width of a flathead screwdriver." Yang Sen found half a hemp rope beside the ditch, with a very special knotting method, "This is a fisherman's knot, rarely seen in rural areas, and may be of the same origin as the hemp rope on the deceased's wrist."

On his way back to the threshing ground at the east end of the village, Yang Sen's footprint light caught something unusual on a patch of moss and lichen. "There's a faint indentation here," he said, parting the lichen to reveal moss lying flat in the same direction. "It's about 0.2 square meters, oval-shaped, with traces of rotation around the edges, like someone placed a heavy object here." Yang Sen used a soil hardness tester to measure the center of the indentation: "Hardness value 60, 20 higher than the surrounding soil, consistent with placing an object weighing over 15 kilograms." He suddenly remembered something, "Could it be a package containing tools used in the crime? The suspect might have opened the toolbox here and taken out a screwdriver."

Near a haystack at the edge of the threshing ground, Yang Lin found several dark red stains, which tested positive for benzidine. "Suspected bloodstains," he said, dabbing the stains with a sterile cotton swab. "The stains are wiping-like, about 5 x 3 centimeters in size, and follow the direction the suspect dragged them. They may have been left by the victim during their struggle." Yang Lin immediately expanded the search area and found a two-hole brown resin button in a crevice of the haystack. The button had wear marks and its shape was exactly the same as the button found in the cellar: "A dark blue fiber was wrapped around the buttonhole, the same fiber composition as the one found on the corn stalks. It should have been snagged from the suspect's clothing."

As the two men sat on the stone mill in the threshing ground, organizing their investigation records, the mountain breeze carrying the sweet scent of corn brushed past their ears. "The clues we've found so far can piece together part of the crime," Yang Lin said, drawing a trajectory on the ground with a twig. "The suspect was wearing size 42 rubber shoes, entered from the west end of the village, dropped a lighter under the old locust tree, dragged the victim along the ditch, breaking corn stalks in the process, dropping buttons and hemp rope, and finally returned to the west end of the village along the same route, stopping to smoke near a haystack." Yang Sen added, "But crucial directional clues are still missing—no murder weapon was found, no complete fingerprints were found, and the connection between the lighter and the buttons still needs physical evidence."

Yang Lin suddenly pointed to the fiber test results in the logbook: "The infrared spectral analysis of this dark blue fiber shows that it contains 70% cotton and 30% polyester, which is a workwear fabric commonly found on construction sites or fishing boats." He paused, "Combined with the fisherman's knot and the 'fishing port' lighter, the suspect may have had experience in the fishing industry, or worked around the fishing port." Yang Sen immediately opened the electronic map: "There is a small fishing port 5 kilometers northwest of the village, where migrant workers are present year-round. The suspect is very likely to have stayed there."

The two decided to split up; Yang Lin went to the fishing port to investigate, while Yang Sen continued searching the village. Yang Lin found several parallel tire tracks in a drainage ditch next to the fishing port, spaced 1.1 meters apart and 9 centimeters wide—typical three-wheeled vehicle tire treads. "The tire tracks are fresh within 72 hours," he said, covering the treads with rubbing paper. "There's a 0.2-centimeter transverse crack on the tread, consistent with the tire tracks on the dirt road at the west end of the village." Yang Sen made a discovery in an abandoned pigsty at the east end of the village—a torn burlap sack with the word "feed" identifiable on the fragments, and DNA from the edge of the fabric matching that found on a cigarette butt.

As the sun set, Yang Lin's investigation bag contained 23 physical evidence samples, and Yang Sen's footprint analysis report was covered with red markings. "To summarize," Yang Lin said, leaning against the trunk of the old locust tree and rubbing his aching back, "there is at least one suspect, male, 165-170 cm tall, wearing size 42 rubber shoes, possibly engaged in fishing or construction-related occupations, and left in a tricycle after committing the crime." Yang Sen added, "But key physical evidence is still missing—no screwdriver or other murder tools were found, no biological samples were identified from the deceased, and the complete contents of the burlap sack fragments still need to be pieced together; a complete chain of evidence cannot yet be formed."

As the last rays of sunlight swept across the cornfields of Wangjiagou, Yang Lin gazed at the cellar entrance cordoned off with police tape. He suddenly recalled the ring-shaped mark on the deceased's neck. "That mark is about 2 centimeters wide, with neat edges," he told Yang Sen. "It's probably from a thin hemp rope, but further examination is needed." Yang Sen packed up his investigation equipment, and Lu Chuan's voice came through his walkie-talkie: "Any major discoveries?" Yang Sen glanced at Yang Lin and replied softly, "I found important traces, but no breakthrough clues yet. Further examination is required."

In the twilight, their shadows stretched long, the beams of their investigation lights flickering on the village road, as if searching for the truth hidden in the darkness. The discovered footprints, fibers, and buttons, though scattered, were gradually, through their analysis, sketching out the suspect's outline. (End of Chapter)