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

"In addition, we also detected a small amount of organophosphate toxin residue in the stomach contents sample of the deceased. The concentration was low. Combined with the digestion of the stomach contents, we judged that the deceased also ingested a small amount of organophosphate toxin during his last meal before death. The murderer may have first made the deceased ingest a small amount of toxin, and then injected the deceased with a high concentration of toxin to ensure that the deceased died quickly and without leaving any survivors."

Upon hearing the news, Zhang Kai's face showed a mixture of solemnity and relief. He was solemn because the murderer's methods were cruel; to ensure the victim's death, two methods were employed: injecting a high concentration of poison and forcing the victim to ingest the poison while eating. The perpetrator was meticulous and possessed extremely strong counter-surveillance awareness. He was relieved because the cause of death had finally been determined, a major breakthrough for the investigation. Combined with the pesticide bottle fragments recovered from the crime scene, this would further narrow down the suspect pool.

"Okay, thank you for your hard work. Continue to refine the toxicology test report, detailing the specific types and concentrations of the toxicants, as well as the times of ingestion and injection. Submit the complete toxicology test report to me as soon as possible, and also send it to Captain Lu," Zhang Kai said seriously.

"Understood, Forensic Doctor Zhang. We will complete the test report as soon as possible and submit it immediately."

After hanging up the phone, Zhang Kai immediately dialed Lu Chuan's number and said urgently, "Captain Lu, we have preliminary results from the toxicology test. The cause of death has been determined: it was organophosphate poisoning, which is consistent with our previous deduction."

Upon hearing this news, Lu Chuan's spirits lifted, and he asked urgently, "Zhang Kai, tell me in detail, what exactly happened?"

"Captain Lu, the forensic team detected high concentrations of organophosphate poison residue in the deceased's bodily fluids, liver tissue samples, and tissue samples around the needle puncture site on his left ankle. This is enough to cause death. This poison has the same composition as the poison in the pesticide bottle containing the dark blue plastic fragment we found next to the body at the crime scene, indicating that the poison used by the murderer was this organophosphate pesticide," Zhang Kai said slowly. "In addition, a small amount of this poison residue was also detected in the deceased's stomach contents. Combined with the digestion of the stomach contents, it is determined that the deceased ingested a small amount of poison during his last meal. The murderer must have first given the deceased a small amount of poison ingestion, and then injected a high concentration of poison to ensure a rapid death without leaving any survivors."

"The needle mark on the victim's left ankle is the mark left by the murderer when injecting poison. The murderer must be skilled in injection techniques or have relevant experience, able to quickly and accurately inject poison into the victim to prevent the victim from struggling or resisting. Based on this, we can further narrow down the suspects. The suspects may be medical personnel, pharmacists, or people engaged in agriculture or animal husbandry who frequently use syringes and are familiar with organophosphate pesticides, such as farmers, agricultural supply store clerks, veterinarians, etc."

"Furthermore, the fact that the perpetrator could easily obtain this organophosphate pesticide suggests that the suspect may be engaged in agriculture-related work or have easy access to agricultural supply stores and pesticide warehouses. This will further narrow down the scope of the investigation. In conjunction with the dark blue plastic fragments extracted from the crime scene, the technical department is currently testing the material and manufacturer of the plastic. Once confirmed, we will be able to find the sales channels for this pesticide and thus identify the suspect."

Lu Chuan listened attentively, nodding and quickly jotting down key information. His tone was tinged with excitement: "Great, fantastic, Zhang Kai! This is a major breakthrough! The cause of death is confirmed, the type of poison is identified, and we can further narrow down the suspects. This is extremely important to us. Have the technical department expedite the completion of the toxicology report, and also speed up the testing of the dark blue plastic fragments to determine the pesticide's manufacturer and sales channels, providing us with more clues to identify the suspects."

"In addition, I will immediately adjust the investigation deployment, and have the investigation team focus on investigating individuals who meet the following characteristics: males aged 30 to 40, about 170 cm tall, with a stocky build, wearing safety shoes or hiking boots of about size 42; familiar with organophosphate pesticides, able to easily obtain such pesticides, and engaged in agriculture, animal husbandry, agricultural input sales, medical care, veterinary medicine, or related work; proficient in injection techniques or have experience using syringes; familiar with the surrounding environment of Zhangjiagou and know the existence of that abandoned cave dwelling; have recently exhibited unusual behavior, such as going out late at night, having suspicious marks on their body, having purchased organophosphate pesticides, or having come into contact with syringes."

"I will also have the surveillance and investigation team focus on checking the surrounding agricultural supply stores, pharmacies, veterinary stations, and hospitals to see if there are any people who match the suspect's characteristics and have recently purchased organophosphate pesticides or syringes, in an effort to find the suspect's whereabouts."

"Don't worry, Captain Lu, I've already urged the technical department. I'll report any test results to you as soon as possible," Zhang Kai said.

"Okay, thank you for your hard work, Zhang Kai. Please keep me informed if there are any further developments."

After hanging up the phone, Lu Chuan immediately convened an emergency meeting with the police officers responsible for visiting and investigating, and monitoring and investigating. He informed each officer in detail of the preliminary results of the toxicology test, adjusted the investigation deployment, clarified the new work priorities, and required all officers to speed up the work progress, focus on investigating suspects who meet the new characteristics, and strive to find clues and lock down suspects as soon as possible.

After the meeting, all police officers resumed their intensive investigation. The door-to-door investigation team conducted a new round of door-to-door investigations in the villages surrounding Zhangjiagou overnight, focusing on questioning villagers about whether anyone was engaged in agriculture, animal husbandry, agricultural supply sales, medical care, veterinary medicine, or related work; whether anyone had recently purchased organophosphate pesticides, handled syringes, or was proficient in injection techniques; and the surveillance investigation team reviewed surveillance footage from nearby agricultural supply stores, pharmacies, veterinary stations, and hospitals overnight to search for the suspect's whereabouts.

Time passed slowly, and before long, night fell. The mountains were shrouded in darkness, with only a few scattered lights dotting the village. The police officers in the door-to-door investigation team braved the night and the cool evening breeze, asking questions from house to house, leaving no detail overlooked. Meanwhile, the police officers in the surveillance investigation team sat in front of their computers, staring intently at the blurry surveillance footage on the screen, reviewing it again and again, not daring to blink, for fear of missing any suspicious figure.

Lu Chuan remained in the branch office without rest. He reviewed the progress of various investigative tasks while awaiting the DNA and plastic fragment test results from the technical department. He knew that the most crucial step now was to identify the victim. Once the victim's identity was confirmed, investigating their social relationships, conflicts, and financial situation would reveal the killer's motive, identify the suspect, and lead to a significant breakthrough in the investigation. (End of Chapter)