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

He gently pricked the wound with a dissecting needle. "The wound is deep enough to reach the dermis. There is a small amount of blood clot at the bottom of the wound. The surrounding skin is slightly red and swollen, indicating that it was formed before death and was close to the time of death. It is speculated that it was caused by the murderer fighting with the victim."

"Teacher Zhang, could this scratch have been caused by the deceased accidentally? For example, by being cut while handling construction tools?" Xiao Lin asked. Zhang Kai shook his head, pointing to the edge of the wound: "The scratch points from the inside of the palm to the fingertip at an angle of about 45 degrees, which doesn't match the direction of force used for self-harm; moreover, there are no probing scratches on the wound, indicating a deep cut that occurred in one go, making it more likely a defensive injury caused by someone else." He added, "We will take tissue samples from the wound and send them to the lab to test for any foreign objects remaining. We will also compare the shape of the utility knife blade retrieved from the scene to confirm whether it was caused by the same tool."

Determining the time of death is the core step in the autopsy. Zhang Kai first examined the rigor mortis: "The jaw joint is completely stiff, making it impossible to open the mouth; the neck muscles are stiff, and the head's range of motion is less than 5 degrees; the stiffness of the shoulder, elbow, and wrist joints of the upper limbs reaches grade IV, and the fingers are in a rigid flexed position; the hip, knee, and ankle joints of the lower limbs are stiff, and the toes are rigid." He compared the results with the rigor mortis development scale, "Based on the location and intensity of the rigor mortis, combined with the ambient temperature (18-20℃) of the underground parking lot of Haotian Building, I initially judged that the time of death was between 24 and 30 hours, that is, between 8 pm on August 22 and 2 am on August 23."

Xiaolin measured the rectal temperature of the corpse with a thermometer: "The rectal temperature is 30.5℃, and the ambient temperature is 19℃. According to the formula for rectal temperature drop (the temperature drops by 0.83℃ per hour after death), the time of death is estimated to be about 26 hours, which is basically consistent with the result of rigor mortis." She added, "However, the corpse is in an underground parking lot with poor ventilation. Could this affect the rate of temperature drop?"

Zhang Kai walked to the autopsy table and lifted the corpse's back: "There are light purplish-red livor mortis areas on the back, shoulder blade area, and buttocks. They do not fade when pressed, have blurred edges, and are diffusely distributed," he explained. "Livor mortis usually begins to appear 2-4 hours after death, enters the diffusion phase 6-12 hours later, and is completely fixed after 24 hours. The livor mortis is now fixed. Combined with rectal temperature and the degree of rigor mortis, the time of death can be accurately determined to be between 10 pm on August 22nd and 1 am on August 23rd, with an error of no more than 1 hour. Environmental factors have little impact on the overall judgment."

The corneal opacity test further narrowed down the time frame. Zhang Kai shone a flashlight into the corpse's eyes: "The cornea is severely opaque, the pupil is completely invisible, and the lens is milky white," he recorded the data. "Corneal opacity is divided into three grades. Severe opacity corresponds to a time of death of 24-36 hours, which is consistent with the previous judgment. Combined with the scattered punctate hemorrhages in the conjunctiva, it is speculated that the deceased may have been in a state of hypoxia before death. An internal autopsy is needed to confirm whether it is related to the cause of death."

Analysis of the stomach contents provided a more precise basis for the time of death. Zhang Kai used a scalpel to make an incision along the midline of the abdomen and carefully separated the stomach wall tissue: "The stomach was empty, with only a small amount of semi-digested rice, meat scraps, and vegetable fiber remaining, about 15ml." He used a pipette to extract a sample of the stomach contents. "The edges of the rice grains were completely dissolved, the muscle fibers of the meat scraps were severely broken, and the vegetable fiber was softened into a paste. Based on the degree of food digestion, it is estimated that the last meal was 4-6 hours before death, that is, between 4 pm and 6 pm on August 22."

“During our visit, we learned that Li Zhiguo ate dinner at the building’s cafeteria at 5 p.m. on the 22nd. The main dish was rice, and the side dishes were braised pork and stir-fried vegetables, which perfectly matched the contents of his stomach!” Xiao Lin immediately took out the visit record. “This further confirmed the time of the last meal. Combined with the previous judgment, the time of death can be locked between 10 p.m. and 11 p.m. on August 22.”

Determining the cause of death requires combining the results of external and internal autopsies. Zhang Kai first examined the neck of the deceased: "There was a 5×3cm band of subcutaneous hemorrhage on the front of the neck. The bleeding area was dark purplish-red in color, and the edges were gradually fading." He used hemostatic forceps to separate the subcutaneous tissue. "The bleeding depth reached the deep layer of the sternocleidomastoid muscle. The muscle fibers were broken in an irregular shape, and there was slight epidermal abrasion on the skin surface corresponding to the bleeding area. This is consistent with the characteristics of a strangulation mark formed by blunt force compression of the neck—the compressing object should be a band-shaped or sheet-shaped object, such as a belt or towel, with a relatively large compression force, resulting in compression of the neck blood vessels and trachea."

Kobayashi pointed to the corpse's ribcage: "The 4th and 5th ribs on the left side of the ribcage are fractured, with sharp fracture ends and obvious displacement." She touched the fracture site with her hand, "There is bleeding and swelling in the tissue around the fracture site, which indicates that the injury was caused before death. It may have been caused by the murderer hitting the chest with a knee or elbow while strangling the neck."

Zhang Kai continued the thoracic dissection, opening the sternum to expose the heart and lungs: "The heart is of normal size, with diffuse punctate hemorrhages under the epicardium and a small number of hemorrhages on the left ventricular wall; both lungs are underexpanded, the lung tissue is dark red with hemorrhages at the edges, and a large amount of foamy fluid oozes from the cut surface." He picked up the lung tissue with forceps, "These are typical characteristics of death by asphyxiation—strangulation compresses the trachea, preventing air from entering the lungs and causing hypoxic asphyxia, while compression of the blood vessels in the neck leads to insufficient blood supply to the brain, accelerating the death process."

"Is a broken rib a fatal injury?" Xiaolin asked doubtfully. Zhang Kai shook his head: "A broken rib is a non-fatal injury. The broken ends did not pierce the heart or lungs, so it will not directly cause death, but it will aggravate the victim's pain, rendering them unable to resist, making it easier for the murderer to strangle them." He added, "A small amount of fiber was extracted from the strangulation marks on the neck. Preliminary testing showed it to be made of cotton and linen, consistent with the composition of the black fibers found in the ventilation vents during the crime scene investigation. It is speculated that the strangulation tool used by the murderer was a strip-shaped object made of cotton and linen, such as a cotton rope or towel."

Other details about the body also provided clues to the case. Zhang Kai found a small amount of skin tissue and black fibers under the fingernails of the victim's right hand: "The skin tissue was initially tested and found to be male skin, which did not match the DNA of the victim's own skin. It is speculated that the victim scratched the murderer during the struggle. The black fibers were consistent with the fiber composition of the vent and the strangulation marks on the neck, further confirming that the murderer carried or used items made of this type of fiber material."

On the inner side of the body's right thigh, Zhang Kai also found a 2×1cm abrasion: "The edges of the abrasion were irregular, with obvious soil residue. The soil composition was exactly the same as that of the soil in the underground parking lot of Haotian Building," he said. He put the soil sample into an evidence bag, "which indicates that the deceased had struggled on the parking lot floor before his death, and the abrasion was caused by friction with the ground, further confirming that the crime scene was in the underground parking lot." (End of this chapter)