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

The police car drove away from the unfinished building in the northern suburbs, heading towards the Municipal Criminal Investigation Detachment. Inside the car, the atmosphere was extremely heavy; everyone's face bore the marks of exhaustion and anxiety. Wang Shuai watched the scenery rushing past the window, his heart filled with worry: the deceased's identity was unknown, there were no leads on the suspect, and there was no surveillance footage in the vicinity—solving this case was incredibly difficult. If the forensic examination results couldn't provide any valuable clues, how could the subsequent investigation proceed?
Upon returning to the Criminal Investigation Division, Wang Shuai immediately led his team to organize the visit records. They entered the identity information of the eight homeless people they had identified into the national population information system for comparison, confirming the identities of six of them. The identities of the other two remained unknown, but they were suspected to be unregistered persons. Subsequently, they notified the nearby police stations and security posts of the vague description of the stranger provided by the convenience store owner, requesting their assistance in the investigation. At the same time, Wang Shuai also arranged for his team to comprehensively retrieve surveillance footage within a 5-kilometer radius of the unfinished building, including intersections, gas stations, banks, and all other locations with surveillance cameras.

However, retrieving the surveillance footage did not go smoothly. Because the northern suburbs are on the outskirts of the city, the surveillance facilities were inadequate; many intersections and locations lacked surveillance cameras. Even where cameras were present, the equipment was either outdated, resulting in blurry images, or the recordings had been overwritten due to short retention periods. The team reviewed footage from over 20 surveillance points but found no individuals or vehicles matching the suspect's description.

Meanwhile, the technical department also reported preliminary test results. The investigators performed DNA typing on the bloodstain samples collected at the scene, confirming that the dripping bloodstains, wiped bloodstains, bloodstains in pools of blood, bloodstains on the knife blade, and bloodstains on the wallet all belonged to the deceased, and no DNA information of the suspect was found. Comparison of the extracted fingerprint samples revealed that the complete fingerprint on the dagger handle and the incomplete fingerprint on the main entrance door frame did not find a match in the national fingerprint information system. Analysis of the extracted fiber samples showed that the gray fibers extracted from the outer perimeter were inconsistent with the black and gray fibers extracted from the area surrounding the body, and their origin could not be determined at this time.

"How could this be?" Wang Shuai frowned upon hearing the test results. "So many traces and physical evidence were collected from the scene, yet none of them directly point to the suspect. Did the suspect wear gloves when committing the crime? Or did he clean the scene?" Yang Lin analyzed, "Judging from the scene investigation, the suspect did not deliberately clean the traces. The dagger still has complete fingerprints, indicating that he may not have been wearing gloves. As for the lack of his DNA information, it's probably because he wasn't injured and there was no blood. Also, the fiber sample is quite special and requires further testing to determine its origin."

Over the next two days, Wang Shuai led his team to expand their search area, visiting all villages, shops, and businesses within a 10-kilometer radius of the unfinished building and checking nearly a hundred people, but still found no valuable clues. The deceased's identity remained unconfirmed, and the keys and wallet found at the scene, after investigation, could not be identified. The wallet was an ordinary black leather wallet without any brand markings, and the key was a common security door key, making it impossible to determine the corresponding residential area or building.

"Captain Wang, this can't go on," Xiao Li said dejectedly. "We've interviewed so many people and reviewed so much surveillance footage, but we still haven't found any clues. The victim's identity is unknown, and we can't find the suspect. Is this case going to become a cold case?" Wang Shuai looked at his team members' tired faces and felt anxious too, but he still forced himself to stay focused and said, "Everyone, hang in there. Solving cases isn't something that can be done overnight. The more difficult it is, the more we need to persevere. Let's review all the clues again and see if we've missed anything."

Subsequently, Wang Shuai organized a meeting for his team to review the clues, going over the on-site investigation, interviews, and the forensic examination results. At the meeting, Xiao Zhang asked, "Could it be that the deceased and the suspect knew each other? Did the suspect specifically lure the victim to the unfinished building to commit the crime, which is why no one in the vicinity saw anything unusual?" Wang Shuai nodded, "That's possible. If it was an acquaintance, the suspect might have known the victim's whereabouts beforehand and chose a secluded location like the unfinished building to commit the crime, making it less likely to be discovered."

“Shouldn’t we start with the deceased’s identity and focus on investigating his social relationships?” Xiao Chen said. Wang Shuai sighed, “The problem is that we can’t even confirm the deceased’s identity right now, so how can we investigate his social relationships?” Yang Lin said, “The keys and wallet found at the scene, while not directly identifying the deceased, might be a starting point. The wallet is black leather and looks relatively new, probably purchased recently; the keys have some wear and tear, indicating they’ve been used for some time. We can check nearby leather goods stores and locksmith shops to see if anyone has sold similar wallets and keys.”

This suggestion was a revelation. Wang Shuai immediately arranged for his team to conduct a comprehensive search of all leather goods and locksmith shops within a 5-kilometer radius of the unfinished building. The team split into two groups, one searching leather goods shops and the other locksmith shops, asking questions at each one. However, the search still didn't go smoothly. Black leather wallets were a very common style, sold in almost all leather goods shops, making it impossible to determine which shop sold them; the keys were also very ordinary, and locksmith shop owners said that these keys were too common to trace their origin.

Time passed day by day, and the investigation made no progress. Wang Shuai's investigation team had been working continuously for a week, and everyone was exhausted, but they still hadn't found any valuable clues. The victim's identity was unknown, there were no leads on the suspects, there was no surveillance footage in the vicinity, and the forensic examination results offered no breakthrough. The case had completely reached a stalemate.

That evening, Wang Shuai sat in his office, staring at the case files on his desk, his heart filled with anxiety. He picked up the crime scene photos, examining each one carefully, hoping to find any overlooked clues. When he saw the key on the deceased's body, he suddenly stopped. Although the key's surface was worn, there seemed to be an extremely tiny mark on the handle, almost invisible without close inspection. Wang Shuai immediately picked up a magnifying glass and examined the key handle closely. Sure enough, there was a very small "福" (fortune) character mark on the key handle, somewhat blurred, but still discernible. (End of Chapter)