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

Yang Lin carefully examined the surface of the machine, hoping to find fingerprints or traces left by the murderer. He gently cleaned the dust off the surface of the machine with a brush and found several clear fingerprints on a mechanical handle.

"There are fingerprints here!" Yang Lin exclaimed excitedly, immediately taking out fingerprint extraction powder and tape, and carefully extracting the fingerprints. The fingerprints were round, with clear lines, and belonged to the index, middle, and ring fingers of the right hand, likely left when someone gripped the handle. "This mechanical handle is in a hidden location, rarely touched by anyone, so these fingerprints are most likely left by the murderer." Yang Lin carefully stored the extracted fingerprint samples and marked them.

Yang Sen found a black metal button on the ground next to the machinery. The button was about two centimeters in diameter, with signs of wear and slightly deformed edges. There were no obvious words or patterns on it, only a small hole on the back, suggesting it was a button from clothing. "This button probably fell off the clothes accidentally during the crime," Yang Sen said. He used tweezers to pick up the button and put it in an evidence bag. "We can have it tested later to see if we can extract the killer's DNA, or determine the button's brand and material."

The two continued their investigation of other areas inside the factory. About five meters from the body, on a shelf, they found an abandoned mineral water bottle. The bottle was covered in dust, but the dust around the opening showed signs of being disturbed. Yang Lin picked up the bottle and examined it closely, discovering several blurry fingerprints on it, similar to those previously extracted from the mechanical handle. "This bottle of water was probably brought by the murderer, who drank from it and then casually placed it on the shelf," Yang Lin said. He immediately extracted the fingerprints from the bottle and placed the entire bottle into an evidence bag, preparing to conduct DNA testing later to see if a saliva sample from the murderer could be obtained.

Yang Sen then found several strands of hair under the shelf. The hair was black, about ten centimeters long, and coarse. He picked up the hair with tweezers and put it into an evidence bag, saying, "These hairs could belong to the deceased or the murderer. We need to do DNA testing to determine that."

At this point, the forensic team's preliminary examination results came back. The forensic doctor approached Yang Lin and Yang Sen and said, "The deceased was male, approximately 30-40 years old, about 175 cm tall, and of medium build. The preliminary cause of death is determined to be a sharp instrument slit in the throat, leading to hemorrhagic shock. There is a clear cut on the neck, approximately 8 cm long and 2 cm deep, with clean edges, consistent with injuries caused by a single-edged sharp instrument. The preliminary time of death is estimated to be 3-5 days ago, but the exact time needs to be confirmed through further examination. There were no obvious signs of resistance on the deceased, suggesting he was killed without warning. Furthermore, the deceased was not carrying any identification documents, and his clothing was worn and tattered, making identification impossible."

Yang Lin and Yang Sen nodded and recorded the preliminary forensic examination results. Afterward, the two conducted a comprehensive search of the other areas of the factory, including the equipment storage areas on the east and south sides, as well as the open area in the center of the factory, checking every corner to ensure no clues were missed. While examining an abandoned conveyor belt on the south side of the factory, Yang Lin found several black fibers in the gaps of the conveyor belt, similar in characteristics to the fibers previously found on the floor of the passageway. He immediately extracted the fibers and placed them in an evidence bag.

Yang Sen then discovered a faint drag mark on the ground next to the conveyor belt. The mark was about two meters long and fifty centimeters wide, with blurred edges, suggesting that someone had dragged a heavy object across the ground. "This drag mark may have been left by the murderer when he dragged the victim to the location of the body," Yang Sen said, taking photos of the mark with his camera and using plaster powder to fix and extract it.

The two continued their investigation until 11:30 a.m., when they completed a comprehensive search of the factory's interior. Following this, they conducted a second, more thorough search, working from the inside out, focusing on areas where evidence had been previously extracted to ensure completeness and accurate labeling, while also checking for any overlooked clues. After this second review, they found no new evidence or traces, only re-extracting and reinforcing some faded traces.

"The on-site investigation is complete. We have collected four suspected suspect footprint models, all from men's size 42 leather shoes with a checkered pattern on the soles and moderate wear; six black fibers, suspected to be wool; three fingerprint samples, from a mechanical handle, a mineral water bottle, and a shelf surface; one black metal button with no obvious markings; five strands of hair; several bloodstain samples; one mineral water bottle; and one drag mark model." Yang Lin, organizing the list of physical evidence, told Yang Sen, "We have collected a lot of physical evidence so far, but we haven't found any key clues that can directly identify the suspect or point to him. The identity of the deceased is also uncertain. We need the technical department to conduct further examination and analysis of the physical evidence, and combine this with the results of our interviews and investigations to gradually narrow down the scope of the investigation."

Yang Sen nodded and said, "Judging from the scene investigation, the murderer had a certain level of counter-investigation awareness. After committing the crime, he did a simple cleanup of the scene, wiping away the bloodstains on the ground in an attempt to cover up the traces, but he still left many clues. The footprints are distinctive, and if the fingerprints and fiber samples can be tested, they will provide us with important directions for the investigation. In addition, the victim had no identification and was dumped in an abandoned factory, which suggests that the murderer may have known the victim, or deliberately dumped the body in a remote place to conceal the victim's identity."

The two carefully collected all the physical evidence and put it into the investigation kit. Then they left the factory and reported the on-site investigation to Lu Chuan. After listening to the report, Lu Chuan frowned and said, "Thank you for your hard work. Send the collected evidence to the technical department for testing immediately and get the results as soon as possible. The investigation team has not yet found any valuable clues. The recent personnel flow in the logistics park is complex, and the factory's remote location has brought great difficulties to the investigation."

"Captain Lu, the footprints, fingerprints, and fiber samples we extracted are very valuable. The forensic team's examination should provide us with more information. Additionally, the mineral water bottle and metal button found at the scene may also be a breakthrough. We can narrow down our investigation by tracing the brand and sales channels of the mineral water bottle and the manufacturer of the button," Yang Lin said. (End of Chapter)