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

To confirm whether there were other potential injuries, Zhang Kai performed a head autopsy: "There was no skull fracture, no intracranial hemorrhage or hematoma, and the brain tissue was normal in morphology, ruling out the possibility of death due to craniocerebral injury; the brain tissue section showed mild edema, which is consistent with hypoxic changes and the pathological characteristics of death by asphyxiation."

As the autopsy neared its end, Zhang Kai summarized all the findings: "The deceased, Li Zhiguo, died from mechanical asphyxiation caused by strangulation; the time of death was between 10 PM and 11 PM on August 22nd; he had engaged in a fierce struggle with the assailant before his death, with defensive sharp object cuts on his left palm, abrasions on his right inner thigh, and scratches on his right hand with his fingernails, leaving traces of skin tissue; cotton and linen fibers were extracted from the strangulation marks on his neck, consistent with the fibers found at the scene; the rib fractures were auxiliary injuries, increasing the difficulty of the deceased's resistance; the stomach contents matched the last meal, further confirming the timeframe of death."

“These conclusions perfectly match the clues from the initial crime scene investigation,” Xiaolin said, organizing the autopsy report. “The cotton and linen fibers, the composition of the soil, the sharp object scratches, and even the suspect’s height range (based on the location of the strangulation marks and the force of the rib fractures, the suspect’s height is estimated to be 183-188cm, consistent with our previous assessment) all connect.” Zhang Kai nodded and handed the autopsy report to the technical department: “Expedited testing of the specific composition of the neck fibers, the DNA in the skin tissue under the fingernails, and the foreign object residue on the palm wounds—these could all be key evidence in identifying the suspect. In addition, we need to test the stomach contents for any drug components to rule out the possibility that the victim was drugged before death.”

As the body was re-covered and wheeled out of the autopsy room, Zhang Kai removed his gas mask, the smell of disinfectant lingering on his face. Looking out at the darkening sky, he recalled the devastating reaction of Li Zhiguo's family when their identities were confirmed. He knew that this autopsy report not only determined the time and cause of death but also provided a clear direction for the investigation—by following the three clues of "cotton and linen strangulation tool," "the killer's skin DNA," and "the source of the sharp weapon," they would eventually find the murderer who killed Li Zhiguo.

When Xiao Lin handed the autopsy report to Lu Chuan, Lu Chuan was reviewing the investigation records of Li Wei submitted by Wang Shuai. "The time and cause of death are clear," Lu Chuan said, his finger tracing across the report. "Now the chain of evidence is becoming increasingly clear. Next, we need to focus on the 'source of cotton and linen fibers,' 'DNA comparison of the murderer,' and 'suspects between 183-188cm in height.' At the same time, we must speed up the investigation into 'Brother Zhang's' identity and Li Wei's whereabouts, and find a breakthrough as soon as possible." He gave orders into the walkie-talkie: "The technical department should prioritize testing the DNA and fiber samples extracted from the autopsy. Zhang Hui will lead a team to re-examine the underground parking lot of Haotian Building, looking for strangulation tools made of cotton and linen. Wang Shuai will continue to investigate 'Brother Zhang,' focusing on screening personnel in the renovation team and property management who meet the height criteria."

As night deepened, the lights in the Criminal Investigation Division remained bright. Zhang Kai's autopsy report was like a key, unlocking the crucial door to solving the case. Everyone knew that every step from now on would revolve around this report, using scientific evidence to bring the murderer to justice and comfort Li Zhiguo's spirit in heaven. Sitting in his office, Zhang Kai looked at the fiber samples on his desk, silently resolving: he must use these minute traces to reconstruct the truth of the case and ensure that this tragedy in the underground parking lot receives a just trial.

At noon on August 25th, the air conditioning in the Criminal Investigation Detachment's conference room blew cool air evenly across every corner. The long conference table was covered with files from the case of the male corpse found in the Haotian Building's underground parking lot. From crime scene photos to autopsy reports and personnel investigation records, the words "Li Zhiguo Murder Case" stood out prominently in large red letters amidst the layers of paper. Lu Chuan sat at the head of the table, his fingertips lightly tapping the surface. His gaze swept over Yang Lin, Wang Shuai, Zhang Hui, and others present. After several days of investigation, although the case had made progress, the key suspect had not yet been identified. This case analysis meeting was precisely to sort through all the clues and find a way to break the deadlock.

“Everyone’s here. Report in turn according to your assigned roles. Let’s start with Yang Lin and talk about the new findings from the expanded on-site investigation.” Lu Chuan’s calm voice broke the silence in the conference room.

Yang Lin immediately stood up and projected the latest crime scene investigation map onto the screen. The newly discovered traces were marked with different colors on the screen: "During the second investigation of the B2 level of the Haotian Building's underground parking lot, we focused on checking the blind spots of the surveillance cameras and the area around the ventilation ducts, and made three key discoveries. First, at the entrance of the ventilation duct behind the parking space where the body was located, we extracted more black cotton and linen fibers, which were completely consistent with the fiber composition found by forensic doctor Zhang Kai at the strangulation mark on Li Zhiguo's neck. In addition, there were a small amount of skin tissue fragments on the fibers, which, according to preliminary testing, were male skin. It is speculated that these were clothing fibers and skin fragments that fell off when the murderer operated the ventilation duct."

He switched to the next photo, which showed a metal fragment hidden in a crevice of rubble: "Secondly, in the pile of rubble next to the elevator shaft on the B2 floor, we found a black plastic fragment with obvious impact marks on the edges. After testing, it was determined to be a bumper fragment from a Toyota Camry sedan. The model number matches the previously speculated '215/55 R17' tire model. There was also a small amount of white putty powder stuck to the fragment, which is the same as the putty powder composition in the B1 floor renovation area. This indicates that the suspect's vehicle had a minor collision near the renovation area, causing the bumper fragment to fall off."

“Third, inside the fire hydrant on the B2 level, a set of blurry size 44 leather shoe prints were found,” Yang Lin pointed to the markings on the survey map. “The shoe prints have a stride length of 80 centimeters, a stride width of 19 centimeters, and a stride angle of 3 degrees outward, which is completely consistent with the shoe prints found next to the body earlier. Moreover, the soil composition on the edge of the shoe prints is consistent with the soil in the parking lot. It is speculated that the murderer had stayed near the fire hydrant, possibly to observe the surrounding environment or to hide the murder weapon.”

"Is it possible to find the suspect through DNA comparison using the fibers and skin tissue found in the ventilation ducts?" Zhang Hui couldn't help but ask. Yang Lin nodded: "The technical department is expediting the processing of the skin tissue fragments to try and extract a complete DNA profile. However, due to the small sample size, the extraction is quite difficult, and there are no clear results yet. In addition, we also found a small amount of dust wiping marks inside the ventilation ducts, suggesting that the murderer may have entered the ventilation ducts, possibly to hide a strangulation tool or to escape the scene. However, the ducts are narrow, only wide enough for one person to crawl through, and the end leads to an abandoned open space outside the building. We are currently investigating the open space, looking for any possible remaining evidence." (End of Chapter)