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

Yang Sen held the footprint light close to the ground and, sure enough, found a set of size 44 leather shoe prints on the cement ground at the edge of the protective net. "Stride length 80 centimeters, stride width 19 centimeters, stride angle 3 degrees outward," he measured with a ruler and looked up at Yang Lin, saying, "It's exactly the same as the shoe prints next to the body on B2. The edges of the shoe prints are also covered with putty powder, and this set of shoe prints extends towards the elevator entrance, indicating that the suspect walked from the renovation area to the elevator entrance, and most likely traveled between B1 and B2 via the elevator."

Among the tools piled up in the renovation area, Yang Lin found a utility knife with bloodstains. "There was fresh blood on the blade, not dried dark red," he said, picking up the utility knife with tweezers and examining it carefully under the light. "The blade is about 10 centimeters long and 1.5 centimeters wide, with a slight notch on the edge. The width and neatness of the edge of the notch basically match the 3-centimeter scratch on the palm of the deceased's left hand. This might be the tool that caused the scratch on the deceased's palm." He put the utility knife into an evidence bag. "It needs to be sent to the laboratory to test whether the bloodstains are related to the deceased, and to compare the shape of the notch on the blade with the scratch."

Yang Sen found a discarded black plastic bag in a corner of the renovation area. "There were several crumpled renovation documents in the bag, which said 'Renovation Project of B1 Floor, Haotian Building,' and the construction company was 'Chengxin Decoration Company.' The date was August 22, which was yesterday," he unfolded the documents and pointed to the signature on them. "The signature is 'Li Wei,' which may be the name of a renovation worker. There was also a small amount of white putty powder at the bottom of the bag, which is consistent with the putty powder on the shoe print. I speculate that this bag was discarded by the suspect. Maybe Li Wei is the suspect, or he is related to the suspect."

Following the trail of shoe prints, the two arrived at the elevator entrance on the B1 level. On the ground next to the elevator doors, Yang Sen found several drops of light brown liquid. A test strip showed a positive result for suspected blood. "The marks are dripping, about 20 centimeters apart, pointing from the elevator entrance towards the renovation area," he said, crouching down to observe the direction of the marks. "They seem to originate from the same source as the bloodstains on the utility knife in the renovation area. It's speculated that the suspect used the utility knife in the renovation area, leaving blood on their hands, which dripped down when they reached the elevator."

The security camera inside the elevator had been broken for several days and could not be retrieved, but Yang Lin found a fragmented fingerprint on the elevator button. "The fingerprint was left on the 'B2' button, with a whorl pattern and 7 feature points remaining," he said, gently brushing the surface of the button with a fingerprint brush. "It matches 3 feature points of the whorl pattern previously extracted from the inside of the silver cufflink. Although it cannot be completely confirmed that it is from the same person, there is a strong correlation, and it needs to be sent to the laboratory for further comparison."

After examining level B1, the two returned to level B2, focusing on checking blind spots in the surveillance cameras and ventilation openings. The ventilation opening on level B2 was located in a corner of the ceiling, about 50 centimeters in diameter. Yang Lin climbed a ladder to get a closer look and discovered that the protective netting around the opening showed signs of having been removed. "There are fresh scratches on the edges of the netting, not from natural aging," he said, shining a flashlight into the opening. "Inside, there are a small amount of black fibers, different from the long black hair found under the body. It looks like some kind of fabric fiber, possibly left by the suspect when their clothing got caught on the netting while moving the body."

Yang Sen then discovered a new set of tire tracks in another corner parking space on the B2 level. "The tire tracks are those of a car tire, model 215/55 R17, presumably a mid-size sedan," he said, using rubbing paper to extract the tire tracks. "There was a small amount of white putty powder embedded in the tire tread, consistent with the composition of the putty powder in the renovation area. Moreover, the trajectory of the tire tracks extends from the parking lot entrance to the corner parking space where the body was located, and then back to the entrance, which matches the timeline described by cleaner Li Guiqin as 'a black sedan quickly entering and exiting.' It is speculated that these are the tire tracks left by the suspect's vehicle."

Yang Lin also found a cigarette butt on the ground next to the tire tracks. "The cigarette butt is a 'Chunghwa' brand, and there are obvious teeth marks on it. A small amount of saliva was extracted from the filter," he said, putting the cigarette butt into an evidence bag. "The cigarette butt's production date is May 2024, so it's relatively fresh. There was no other debris on the ground next to it, so it's speculated that the suspect discarded it when he parked and moved the body. The saliva can be used to extract DNA, and if it can be matched with fingerprints or bloodstains, the suspect's identity can be confirmed."

At 2 PM, the two completed their investigation of the entire underground parking lot, collecting eight new clues: "size 44 leather shoe print (B1 level)," "utility knife (with bloodstains)," "black plastic bag (containing renovation documents)," "suspected bloodstains (elevator entrance)," "fingerprints on elevator buttons," "fiber from ventilation vents," "car tire tracks," and "Zhonghua cigarette butts." Yang Lin leaned against a pillar on B2 level, took out his investigation log, and reviewed each clue: "We're getting more and more clues, but most require lab testing to confirm their relevance. For example, whether the bloodstains on the utility knife belong to the deceased, whether the DNA from the cigarette butt matches the fingerprints, and the specific car model corresponding to the tire tracks—we can't yet form a complete chain of evidence."

Yang Sen sat on the ground, wiping the sweat from his brow. "The deceased's identity remains a mystery. Apart from a silver cufflink, there are no other items that can confirm the identity. The cufflink is engraved with the letter 'L,' so perhaps the first letter of the deceased's surname is 'L,' but that's too broad a range and difficult to investigate." He flipped through the renovation invoices. "Li Wei from Chengxin Renovation Company is a suspicious person. We need to contact this renovation company as soon as possible, find Li Wei, and verify his identity information and whereabouts during the time of the incident."

"There's also the 'black sedan with one taillight not working,' mentioned by the cleaner," Yang Lin added. "The tire tracks we extracted are model 215/55 R17, which corresponds to mid-size sedans such as the Toyota Camry and Honda Accord. We need to work with the vehicle management office to investigate sedans of this model with damaged taillights throughout the city that have recently been seen entering or leaving the underground parking lot of Haotian Building, in order to narrow down the search for suspect vehicles."

The two men organized their investigation records and reported to Lu Chuan via walkie-talkie: "The expanded investigation yielded eight new clues, all of which need to be sent to the laboratory for testing to confirm their relevance; a suspicious person named 'Li Wei' (Chengxin Decoration Company) and suspicious vehicle characteristics were discovered (medium-sized sedan, damaged taillights, tire model 215/55 R17); the identity of the deceased is still unclear, and we can only infer the possible surname from the letter 'L' on the cufflink."

Lu Chuan replied on the walkie-talkie: "Immediately send all evidence to the technical department for expedited testing. At the same time, arrange for someone to contact Chengxin Decoration Company to verify Li Wei's identity and whereabouts. Wang Shuai is already retrieving municipal surveillance footage from the area around the parking lot, focusing on mid-sized sedans with damaged taillights. You two will remain at the scene to cooperate with the technical department in the follow-up investigation to ensure no clues are missed." (End of Chapter)