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

"Okay, thank you for your hard work," Lu Chuan said. "You haven't rested all night, so go back and get some rest first. Contact me if you have any news."

"No need, Captain Lu. Let's go back and organize the autopsy materials and wait for the lab's final test results. We'll report back to you immediately if we have any news," Zhang Kai said. He knew that solving the case was urgent and every minute was precious. He didn't want to waste time and just wanted to provide more clues for the case as soon as possible.

Lu Chuan nodded, offering no further advice, and said, "Alright, then you all take care and don't overwork yourselves. Wang Shuai, come here, we need to hold an emergency meeting to adjust our investigative approach based on the autopsy results and to plan our subsequent investigative work."

"Understood, Captain Lu!" Wang Shuai immediately stepped forward and followed Lu Chuan to the conference room. The other team members also rushed to the conference room to attend the meeting.

Zhang Kai and Xiao Lin turned and left Lu Chuan's office, returning to the Provincial Criminal Investigation Detachment to organize the autopsy materials and await the final laboratory results. They remained silent the entire way. They knew that although the time and cause of death had been determined, the victim's identity was unknown, the suspect had not yet been identified, and the case investigation still faced many difficulties. They had to do their utmost to complete the subsequent examinations and provide more clues for the investigation.

Upon returning to the Provincial Criminal Investigation Detachment, Zhang Kai and Xiao Lin immediately went to the laboratory to inquire about the progress of the toxicology and DNA testing. The laboratory staff, who were diligently conducting their tests, immediately reported to their supervisor upon seeing Zhang Kai and Xiao Lin enter: "Forensic Doctor Zhang, the specific type of organophosphorus pesticide has been identified as methamidophos, a highly toxic organophosphorus pesticide. The concentration of methamidophos in the deceased's body was 120 mg/kg, far exceeding the lethal dose of 20 mg/kg. It can be confirmed that the deceased died from methamidophos poisoning. The time of death is consistent with your initial assessment, between 11:00 AM and 12:00 PM on [Month] [Day].

"The DNA testing is still ongoing. We have entered the deceased's DNA sample into the missing persons database for comparison. We have already compared some missing persons information and found no match. We are continuing to compare and expect to complete all the comparisons and obtain the final results around 3 p.m. this afternoon."

Zhang Kai nodded and said, "Okay, thank you for your hard work. Speed ​​up the DNA testing and let me know immediately once the comparison is complete. Also, compile the test report for methamidophos; I need to report to Captain Lu Chuan immediately."

"Understood, Forensic Doctor Zhang!" the laboratory staff replied, immediately speeding up the testing process and compiling the test report.

Xiao Lin, meanwhile, was organizing the autopsy materials, adding the final toxicology test results to the autopsy report to ensure its accuracy and completeness. Zhang Kai, sitting nearby, carefully considered the details discovered during the autopsy. The deceased died from methamidophos poisoning, a highly toxic pesticide mainly used in agriculture for pest control, difficult for ordinary people to obtain. The fact that the suspect was able to obtain methamidophos suggests he might be involved in agriculture or have access to this pesticide, which could be a crucial clue in identifying the suspect.

"Teacher Zhang, why did the suspect use methamidophos to kill the victim? Methamidophos is highly toxic, causes rapid death, and leaves obvious traces. Why didn't the suspect choose other, more discreet poisons?" Xiaolin asked after finishing organizing the materials.

Zhang Kai thought for a moment and said, "There are two possibilities. One is that the suspect only had methamidophos on hand and no other poisons, so he chose to use methamidophos to poison the victim. The other is that the suspect deliberately chose methamidophos to kill the victim quickly and without considering the issue of leaving traces. Perhaps he thought that moving the body to the subway construction site would cover up the crime and prevent us from finding any clues. In addition, although methamidophos is highly toxic, it is relatively easier to obtain than other highly toxic substances. For example, some agricultural supply stores and pesticide stores may sell it, and the suspect may have obtained it from these channels."

"Then could we suggest that Captain Lu arrange for his team to investigate all agricultural supply stores and pesticide shops in the city to see if anyone has recently purchased methamidophos, especially men between the ages of 30 and 35? This might help us identify the suspects," Xiao Lin said.

“Yes, that’s a good suggestion.” Zhang Kai nodded and said, “When we get the final DNA test results and report to Captain Lu Chuan, we’ll bring up this suggestion. In addition, we need to compare the fiber samples extracted from the autopsy with the fiber samples extracted from the crime scene to see if there is any connection and to determine the source of the fibers. This could also be an important clue to identify the suspect.”

Subsequently, Zhang Kai and Xiao Lin began comparing the fiber samples extracted from the autopsy. They placed the black and brown fibers extracted from the autopsy with the fiber samples collected from the scene investigation under a microscope, carefully observing the morphology, structure, and material of the fibers, comparing them one by one. After more than an hour of comparison, they found that the black fibers extracted from the autopsy were completely consistent in material with the black fibers extracted from the bottom of the fence and discarded plastic film at the scene, both being cotton fibers; the brown fibers extracted from the autopsy were completely consistent in material with the brown fibers extracted from the weeds in the vacant lot and cement bags at the scene, both being synthetic fibers. This indicated that these fibers were likely shed when the suspect came into contact with the deceased, further confirming that the suspect had close contact with the deceased, and providing important clues for solving the case.

At 10:00 AM, the laboratory staff completed the test report on methamidophos and handed it to Zhang Kai. After carefully reviewing the report and confirming the accuracy of the results, Zhang Kai immediately called Lu Chuan to report the final toxicology test results: "Captain Lu, the laboratory's final toxicology test results are in. The organophosphorus pesticide in the deceased's body was methamidophos, with a concentration of 120 mg/kg, far exceeding the lethal dose. We have determined that the deceased died from methamidophos poisoning, and the precise time of death is approximately 11:30 AM on [Month] [Day]. Furthermore, we compared the fiber samples extracted from the autopsy with those extracted from the crime scene investigation and found that the two materials are completely identical, indicating that these fibers were likely shed by the suspect, providing a clue for solving the case."

On the other end of the phone, Lu Chuan sounded excited: "Great, fantastic, Forensic Doctor Zhang! This result is extremely important to us. Methamidophos is a highly toxic agricultural pesticide, difficult for ordinary people to obtain. We'll immediately arrange for team members to investigate agricultural supply stores and pesticide shops throughout the city, focusing on people who have recently purchased methamidophos, especially men between 30 and 35 years old. We'll also investigate anyone who had contact with the deceased and could have obtained methamidophos, trying to identify the suspect. Also, when will the DNA test results be available?" (End of Chapter)