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

"The impact was relatively minor, likely caused by the collision during the struggle for asphyxiation, and is not the primary cause of death." The skin at the site of the hematoma showed contusions but no lacerations, indicating that the impact was not severe and had little impact on the death process.

“Teacher Zhang, look at the deceased’s hands,” Xiao Lin suddenly pointed to the corpse’s palms. “There are multiple areas of skin abrasion and bruising on the palms and fingertips, and there are fiber residues under the fingernails.” Zhang Kai used a probe to examine the fingernails and extracted a small amount of blue fibers and skin tissue. “These injuries were formed before death and are consistent with the characteristics of a struggle. The fibers and skin tissue under the fingernails need to be analyzed for DNA and composition; perhaps we can find the suspect’s biological information.” He noticed that the nail of the deceased’s right index finger was broken, with an irregular end and fresh bleeding at the edge, further confirming that a struggle had taken place before death.

The clothing inspection revealed a crucial clue. The collar of the blue polyester overalls had a tear, with uneven edges, suggesting it had been violently ripped. "The tear in the collar went from left to right, consistent with the force characteristics of being pulled from the left," Zhang Kai measured the tear length. "The fibers at the tear showed obvious stretching and breakage, indicating it was torn before death." A small amount of rust particles were found in the left breast pocket of the overalls, with a composition consistent with the rust on the inner wall of the water tank, indicating that the body had rubbed against the tank wall while inside.

"Based on these findings, the cause of death can be basically determined," Zhang Kai said, using hemostats to pick up the neck tissue specimen and carefully examining it under the operating light. The hemorrhages in the sternocleidomastoid muscle appeared dark brown under the infiltration of formalin. "Mechanical asphyxiation, specifically strangulation. Look at the distribution of these muscle hemorrhages, extending from the greater horn of the hyoid bone to the supraclavicular fossa, showing continuous damage," he said, turning the specimen to Xiaolin. "This is a typical characteristic of strangulation force. The perpetrator must have pressed the sides of the neck with their thumbs, while the other four fingers applied pressure at the back of the neck, causing simultaneous occlusion of the airway and blood vessels."

He put down the specimen and picked up the X-ray of the deceased's right hand: "The deceased clearly resisted a struggle before death, which can be confirmed by the injuries to the palm and the residue under the fingernails. The epidermis of the palm and fingertips is peeled off in patches, with the largest area reaching 2×1.5cm, and the edges are curled, which is a typical abrasive resistance injury," Zhang Kai marked on the photo with a red pen, "especially the contusion at the base of the thumb, which reaches the dermis, indicating that the person had gripped an object forcefully—most likely the perpetrator's arm or clothing."

Kobayashi adjusted her glasses, her gaze falling on the fingernail specimen on the autopsy table: "The blue fibers in the fingernail crevices have been sent for infrared spectroscopy analysis, and the preliminary assessment is that they match the polyester fibers found at the scene. But I still have questions," she pointed to the photos of the water tank scene, "Why was the body found in the water tank? Was it disposed of after death or did the body fall into the water before death? After all, there was water in the tank, and there was foam around the deceased's mouth and nose, which could easily lead people to mistakenly believe it was drowning."

Zhang Kai walked to the other side of the autopsy table and carefully opened the deceased's lips. On the moist oral mucosa, several pinpoint-sized bleeding points were clearly visible, like a handful of red sand sprinkled on top. "Look closely at the foam around the mouth and nose," he said, gently picking up the foam with a probe. The white foam was flocculent and had poor fluidity. "There is very little of this mushroom-shaped foam, and it doesn't form the large amount of white foam typical of drowning. It's more like respiratory secretions mixed with water after death."

He picked up a scalpel and made a transverse incision in the upper trachea. The mucous membrane between the cartilage rings was pale red with a small amount of mucus attached. "There was indeed a small amount of drowning fluid in the trachea and bronchi," Zhang Kai said, using a pipette to extract a liquid sample. "But the amount was very small, with a total volume of no more than 5 ml, far below the amount of fluid required for drowning. Moreover, under a microscope, the sediment particles in this fluid were sparsely distributed and did not form widespread alveolar deposits." He pulled up a photograph of an alveolar section. "The alveolar structure of normal lung tissue was intact, and no alveolar dilation and rupture phenomena characteristic of drowning were observed."

Xiaolin examined the tracheotomy closely and found no obvious congestion or edema on the mucous membrane surface. "Then where did this drowning fluid come from?" she asked. "If it wasn't inhaled before death, could it have entered after death?" Zhang Kai nodded and pressed his fingers against the deceased's chest cavity: "After death, the body is thrown into a water tank. Due to the pressure difference within the chest cavity, a small amount of water will enter the respiratory tract through the mouth and nose, but it cannot reach the deep alveoli. Look at the bifurcation of the bronchi; there is obvious gravitational sedimentation of the fluid here," he pointed to the meniscus formed by the liquid surface, "This is a typical characteristic of post-mortem fluid inflow, not active inhalation before death."

To further confirm this, Zhang Kai cut open the stomach wall, and the stomach contents were spread out on the dissection tray, with rice grains and vegetable fibers clearly visible. "There was no drowning fluid in the stomach, which is one of the key pieces of evidence to rule out drowning," he explained. "People who fall into the water before death often inhale liquid into their stomachs due to violent coughing, forming stomach drowning fluid. But the dryness of the stomach contents in this body is consistent with the time of death, and there is no abnormal increase in water content."

He picked up the deceased's lung specimen, weighed it on an electronic scale, and recorded: "Left lung weighs 480g, right lung weighs 520g, total weight 1000g, within the normal range, without the edema and weight gain seen in drowning." Zhang Kai cut open the lung tissue with a scalpel; the cut surface was dark red, and when squeezed, no large amount of foamy liquid overflowed, only a small amount of bloody liquid seeped out. "The buoyancy test of the lung tissue was also negative; after being placed in water, part of it sank, which does not conform to the floating characteristics of lungs filled with air and liquid during drowning."

Looking at the autopsy evidence, Xiaolin's doubts gradually cleared: "So, the deceased was indeed strangled to death before being thrown into the water tank by the murderer? Why would the murderer do that?" Zhang Kai put down the lung specimen and picked up the deceased's clothing: "Hiding the body in the water tank could delay its discovery and also use the water environment to interfere with determining the cause of death, attempting to disguise it as an accidental drowning or suicide." He pointed to the mud stains on the work pants, "The mud and sand on the inside of the trouser legs are unevenly distributed, with obvious wiping marks, indicating that the body was dragged, further confirming that it was moved to the water tank after death."

He walked to the computer and pulled up a 3D reconstruction image of the neck skin. The three-dimensional shape of the finger marks was clearly presented on the screen: "Based on this chain of evidence, it can be definitively determined that the deceased was strangled to death elsewhere, the process lasting approximately 3-5 minutes. Afterward, the murderer dragged the body to the water tank, threw it into the water through the maintenance opening, and blocked the overflow pipe to delay discovery." Zhang Kai zoomed in on a finger mark in the image. (End of Chapter)