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

When the two returned to the scene, Lu Chuan was discussing the preliminary plan for the village investigation with Wang Shuai. After Yang Lin and Yang Sen reported the newly discovered evidence and investigation results, Lu Chuan took the evidence bag they handed him. Looking at the tire track model, fibers, cigarette butts, and metal hooks inside, he frowned slightly: "There are more clues than before, but the core issue remains unresolved; the identity of the deceased is still unknown. However, your findings are not without value. At least you've determined the type of vehicle the suspect might have used and the area of ​​their activity, providing direction for the subsequent village investigation."

“Next, these pieces of evidence must be sent back to the technical section of the detachment immediately,” Lu Chuan instructed Yang Lin and Yang Sen. “Prioritize testing the specific vehicle model of the tire tracks, the material source of the fibers, the DNA on the cigarette butt, the composition of the stains on the metal hook, and the properties of the two powders, especially the DNA. If we can extract the suspect’s DNA, even if we can’t identify the deceased for the time being, we can narrow down the scope of the investigation. In addition, the investigation route map you draw must clearly mark the location of each trace found to facilitate subsequent re-examination.”

Yang Lin and Yang Sen nodded, carefully placing the evidence into a special evidence box, preparing to send it to the branch office. The sun gradually set, and the surface of the Beihe River shimmered with golden light. Looking at the calm river before them, the two knew that although this expanded investigation had uncovered many traces and clues, there was still a long way to go before identifying the deceased and the suspects. However, they were not discouraged. Every discovery was a step closer to the truth; as long as they persisted in meticulous investigation, they would eventually unveil the mystery of this floating corpse case in the Beihe River.

On the way back to the branch, Yang Sen looked at the villages passing by outside the window and said to Yang Lin, "Hopefully the technical department can find useful information from these pieces of evidence, especially the DNA on the cigarette butts and the stains on the metal hooks. If we can find the suspect's DNA, or confirm that the stains are the victim's blood, the case will take a turn for the better."

Yang Lin nodded: "Yes, and those two powders, if we can find their source, we might be able to determine the suspect's occupation. For example, the white powder is cement, and the brown powder is paint, so the suspect might be a construction worker or a decorator. This would further narrow down the scope of our investigation. When we get back, let's not be idle. Let's go through all the traces at the scene again and see if there are any missing connections. Sometimes, seemingly unrelated details can be pieced together to form a complete chain of clues."

The police car drove into the gates of the Criminal Investigation Division, and two officers carried a box of evidence straight to the technical section. Although the case was still at a standstill, they firmly believed that these traces, painstakingly unearthed from the banks of the North River, would eventually become the key to solving the mystery, exposing the crimes hidden beneath the calm surface of the river.

At 2 PM, the temperature control system in the Criminal Investigation Detachment's autopsy room remained stable at 16°C, and the filtration system operated at full capacity to try to dilute the putrid odor from the floating corpse. A refrigerated truck carrying the body from Beihe slowly drove into the passageway. Two staff members, wearing heavy biosafety suits, carefully lifted the dark canvas bag containing the body onto the autopsy table. The bag was still covered with seaweed and mud, and the nylon rope at the opening was tightly tied, making a creaking sound when untied. The swollen and deformed outline of the body inside the bag was vaguely visible.

"Prepare the dissection instruments. Begin with a surface examination of the body, focusing on recording signs of putrefaction, injuries, and any substances adhering to the surface, especially changes related to immersion in water." Zhang Kai, wearing double-layered latex gloves, spoke through his gas mask, his voice deep yet exceptionally clear and professional. His assistant, Xiao Lin, had already arranged the dissection trays in order; scalpels, forceps, bone saws, and other instruments gleamed coldly under the operating lights. Specimen bottles beside them contained saline solution and preservatives, ready to collect various samples at any time.

Xiaolin carefully cut open the canvas bag with scissors, gradually revealing the full body. The body was in a state of moderate to high decomposition; the skin was white and wrinkled from prolonged immersion, exhibiting typical "laundry woman's hands" characteristics. Some skin had separated from the muscle tissue, threatening to fall off with the slightest touch. "The deceased is male, initially estimated to be between 40 and 50 years old, 175cm tall, calculated based on femur length measurements, with an error margin of no more than 1cm." Xiaolin measured various parts of the body with a soft ruler while quickly writing on the record board. "The rigor mortis has completely subsided, and the joints are relaxed, indicating that the time of death has exceeded 72 hours; the livor mortis is dark purplish-red, distributed on the back, buttocks, and unpressed areas of the limbs, and does not fade when pressed, consistent with the characteristics of livor mortis fixed more than 24 hours after death, but due to immersion in water, the color of the livor mortis is slightly lighter than that of a normally decomposed body, and the edges are more blurred."

Zhang Kai squatted beside the autopsy table, gently puncturing the putrefactive bubbles in the corpse's abdomen with a dissecting needle. Brownish, putrefactive liquid slowly flowed out, carrying a pungent odor of hydrogen sulfide mixed with the fishy smell of river water. "Immediately take samples to test the gaseous components in the putrefactive liquid, paying particular attention to the concentration ratio of hydrogen sulfide and ammonia," he instructed Xiao Lin. He then used tweezers to pick up a piece of sloughed skin tissue and carefully examined it under the operating light. "The skin is grayish-white, indicating that putrefaction has entered an active phase. However, due to the prolonged exposure to the low temperature in the water (the recent water temperature in the Beihe River is about 15℃), the putrefaction process is slower than in a normal temperature environment. Scattered putrefactive veins are visible in the chest and abdomen, distributed in a tree-like pattern, which is typical of 4-6 days after death. In addition, the greenish tinge from the lower right abdomen has spread to the waist. Based on the correlation formula between the rate of greenish tinge diffusion and water temperature, combined with the influence of the Beihe River's current speed of 0.3 meters per second on putrefaction, we preliminarily judge that the putrefaction process has lasted for 5-7 days."

"Should we combine entomological evidence to further narrow down the time of death?" Xiao Lin pointed to the small aquatic insects remaining in the hair and clothing crevices of the corpse. "There are a few midge larvae at the base of the hair, and a few water flies in the folds of the clothing. Perhaps we can make a precise judgment by analyzing their developmental cycles." Zhang Kai nodded, indicating that Xiao Lin should collect insect samples in a special specimen bottle: "At a water temperature of 15℃, midge larvae take 3-4 days to develop from eggs to the third instar larvae, while water flies have a slightly longer developmental cycle, about 4-5 days. Combining this with the 5-7 day range of decomposition characteristics, we can comprehensively judge the time of death to be between 0:6 and 3:3 AM six days ago, with an error margin of within 12 hours."

Xiao Lin asked疑惑地, "How exactly is the impact of water temperature on determining the time of death quantified? We've mostly dealt with land-based decomposing corpses; we have relatively less experience with underwater corpses." Zhang Kai took out his copy of the *Atlas of Forensic Pathology* and turned to the "Table of Decomposition Processes in Water": "For every 1°C decrease in water temperature, the rate of decomposition slows down by approximately 10%-15%. The recent average water temperature in the Beihe River is 15°C, which is 10°C lower than the normal ambient temperature of 25°C. Therefore, the decomposition process is 1-1.5 times slower than that of land-based corpses." (End of Chapter)