frightfiction Chapter 1164 Arrangements to Expand the Scope of On-site Investigation
Chapter 1164 Arrangements to Expand the Scope of On-site Investigation
“A black fiber, 6-8 cm in length, was extracted,” Xiao Yang placed the fiber sample on a glass slide and observed it under a 40x stereomicroscope. “It’s made of polyester, with an irregular triangular cross-section and a single fiber linear density of 3.2 dtex, the same as the fiber composition found in the recessed area of the tombstone, but its breaking strength is 4.5 cN/dtex, 1.2 cN/dtex higher than before, indicating it came from the lining of the suspect’s coat.” He wiped the inside of the chain lock with an alcohol swab. “The metal residue on the lock needs to be analyzed by energy dispersive spectroscopy in the lab, with a focus on detecting any skin tissue transfer.” The two searched along the direction of the chain with a radius of 5 meters and found a discarded 600D Oxford cloth black bag in a thicket of jujube brambles 10 meters away. The red soil on the polypropylene drawstring at the bag’s opening was completely consistent with the X-ray diffraction pattern of the soil from the grave.
On the way back to the main road of the cemetery, Xiao Sun made a new discovery on the bluestone path next to the incense and candle stall. “At 36°42′15″N, 117°25′30″E, there is an overlapping shoe print, covered by seven layers of later footprints,” he said. He used an electrostatic precipitator at 15kV to extract trace amounts of material from the shoe print. “The white powder adhering to the edge of the shoe print has a particle size distribution of 10-50mm. X-ray fluorescence spectroscopy shows that it contains 32% CaO and 60% SiO2, which is the mixed ash of calcium carbonate and silica from burning incense.” Xiao Yang found half a latent blood fingerprint under the stone table where the stall owner was bargaining. After being developed with 502 glue, it showed pale yellow lines: “The central pattern is a whorl pattern with eight identifiable feature points, including three small bridges and two small eyes. The spacing between the lines is 0.2-0.3mm. The residual incense ash particles show that it is a planar contact fingerprint, consistent with the pressing action when buying incense.”
When the search extended to the cemetery wall, Xiao Yang stopped outside a section of damaged barbed wire with a 15x20cm mesh. A 2x3cm piece of black cloth was hanging from the high-carbon steel spikes of the wire, with a 45° tear at the edge. "The cloth is a 2/1 twill weave, with a warp density of 28 threads/cm and a weft density of 24 threads/cm," he determined after measuring with a fabric density microscope. "The tear is irregularly serrated, with fibers pulled out 1-3mm in length, caused by being forcibly caught by 0.8mm diameter spikes, consistent with the scraping characteristics when climbing over the wall. The infrared spectrum of the cloth shows it contains 85% polyester and 15% spandex, consistent with the previously found fiber composition." On the dirt road outside the wall, Xiao Sun found more overlapping size 43 shoe prints, with a stride length 2±0.3cm shorter than in the cemetery: "The suspect's stride frequency increased from 72 steps/minute to 85 steps/minute when leaving, and the standard deviation of stride width increased by 0.5cm, consistent with the gait characteristics of accelerating away after committing the crime."
Around the hut of Old Zhang, the tomb keeper, the investigation yielded even more important discoveries. The dust layer (0.15mm thick) on the windowsill showed obvious signs of wiping, exhibiting unidirectional linear stripes. Sweat fingerprints on the window frame, revealed by fluorescent powder, showed clear lines: "This fingerprint has 8 stable feature points, 5 of which match the fingerprint under the stone table. The urea concentration in the sweat is 0.8mg/dL, consistent with the characteristics of an adult male." Xiao Sun found a Yuxi brand cigarette box in the garbage heap behind the hut. After multiple wiping and extraction, the STR typing of saliva stains on the inside of the cigarette box was amplified at 16 loci: "The plastic lining of the cigarette box contained 0.3mg/g of nicotine, consistent with the 32mg tar content of the cigarette butt found at the base of the tombstone, indicating they belong to the same batch of products."
Around noon, the search area had expanded to the farmland surrounding the cemetery. Xiao Yang discovered a series of blurry tire tracks in a winter wheat field. A laser profilometer scan revealed a tire width of 18±0.5cm, typical of a 90/90-18 motorcycle. "The center-to-center distance of the tracks is 120±2cm, and the wheelbase is 135cm, consistent with a men's motorcycle," he said, covering the tire tracks with rubbing paper. "The tread depth is 1.2mm, the wear uniformity is 85%, and the estimated mileage exceeds 50,000 kilometers. The clear layering of red soil and incense ash in the rut grooves indicates the engine was not turned off when parked." Xiao Sun found a silver snap fastener with a diameter of 18mm in a ditch beside the tracks. It had four round holes, and the chrome plating was 90% intact, matching the composition of the button found under the cypress tree. The gray fibers wrapped around the buttonholes were 12cm long and, under a microscope, showed obvious twisting characteristics.
While organizing the findings, the two sat on a stone bench in the cemetery, with the evidence bags in front of them arranged in a straight line 2 meters long according to the chain of evidence. “The 37 pieces of evidence in 12 categories discovered so far can be linked together to form a complete movement trajectory,” Xiao Yang drew a route map using coordinates on a waterproof notebook. “The suspect entered from the back mountain path between 3 and 5 a.m., bought offerings at an incense and candle stall (cigarette butts and incense ash as evidence), dug the grave of Zhou Guiying with a flat-headed shovel (metal fragments and shovel marks as evidence), hid the iron chain, and escaped by climbing over the broken wall (fabric fibers and shoe prints as evidence), and finally left on a men’s motorcycle (tracks and wheelbase as evidence).” Xiao Sun printed a list using an evidence labeling machine: “23 size 43 shoe prints were extracted (including 3 three-dimensional footprints), 56 black polyester fibers (12 of which had dye particles), 2 fingerprints (both left index fingers), 2 cigarette butts (saliva stain DNA is being tested), 1 section of iron chain (metal residue from the buckle is to be analyzed), 1 cloth bag (3 potential fingerprints were extracted from the surface), and 17 trace material samples (including soil, fiber, ash, etc.).”
“But there are still gaps in key indicative clues,” Xiao Yang frowned, marking the list in red pen. “The murder weapon, a flat-headed shovel, has not been found; the body's identification information is missing; the suspect's fingerprints do not match in the criminal record database; the production batch number of the chain needs to be traced; and the manufacturer's label on the cloth bag is worn away.” He sealed the last fiber sample into an anti-static bag. “Although these polyester fibers have the same composition, they lack unique dye chromatographic characteristics, making it impossible to directly point to a specific clothing brand.” Xiao Sun added, “The bare feet in the shoe prints suggest a height of 175-180cm and a weight of 65-70kg, but no specific wear characteristics were observed; the motorcycle tire treads require checking 3.2 registered vehicles of the same model throughout the city, which is a significant workload.”
As the technicians packed all the evidence into shockproof crates, Li Ming approached, his boots tapping rhythmically on the stone slabs. Looking at the two crates full of evidence bags labeled red, he asked, "Any breakthroughs?" Xiao Yang shook his head and uploaded the investigation data to the evidence management system: "A systematic chain of trace evidence has been discovered, but all require further laboratory testing. Currently, no biological evidence or specific markers have been obtained to directly identify the suspect." Xiao Sun retrieved the electronic record: "However, the criminal profile constructed from 17 parameters indicates that the suspect should be male, aged 25-40, familiar with the cemetery terrain, with experience in horticulture or construction, and may have recent damage to his left finger joints (incomplete fingerprint features). These factors can narrow down the investigation scope by 60%."