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

Wang Shuai took the evidence bag and looked at the fibers inside: "What type of tire tracks are there? Can we confirm that it's a handcart from the logistics park?"

Yang Sen took out his notebook, on which he had drawn a sketch of the wheel tracks and their dimensions: "The tracks are 15 centimeters wide and 60 centimeters apart, exactly the same size as the wheels of the small handcarts in the logistics park. We've already asked Zhang Jianjun, and he said there are 10 such handcarts in the logistics park, usually kept in the freight area. One was missing yesterday afternoon and was only found this morning in a corner near warehouse number 13—Zhang Jianjun said he thought it was just a worker who hadn't put it back after using it and didn't pay attention. Now it seems that the suspect may have used that handcart to move the body!"

Lu Chuan's eyes sharpened: "Investigate that handcart immediately! Extract rubber scraps from the wheels and compare them with the tire tracks in the passageway. Also, check the handcart for any remaining bloodstains, fibers, or brown mud—these are crucial pieces of evidence. Furthermore, what lies outside the west wall? Are there any security cameras or residents there?"

Yang Lin replied, "There is a wasteland outside the wall with no residents, but there is a small road 500 meters south that connects to the main road in the suburbs. There are traffic cameras on the main road. We can check the surveillance footage of that small road to see if any suspicious people or vehicles passed by before or after the incident, especially people pulling packages that look like corpses or pushing carts."

“Okay!” Lu Chuan nodded. “Yang Lin, you and Yang Sen go and investigate the handcart now. Collect all possible evidence, and then send the wheel tracks, fibers, and brown soil samples back to the branch's technical section for expedited analysis, especially the composition of the fibers, the source of the soil, and the correlation between the wheel rubber debris and the passage marks. Yang Sen, when you are investigating the handcart, focus on checking the inside of the cart for drag marks. The suspect may have left friction marks by putting the body in the cart.”

The two men accepted the order and immediately headed to the logistics park's freight area. The lights in the freight area were already on, and a small red handcart sat forlornly in a corner, its body covered in dust, but the dust inside the cart's cargo bed showed obvious signs of disturbance. Yang Lin put on gloves and gently stroked the inside of the cargo bed: "There's an arc-shaped friction mark here, about the same width as the deceased's body. It must have been left when the body was placed in the cargo bed and dragged around."

Yang Sen took out an adhesive sampler and collected a dust sample from the inside of the cart: "Let's extract the dust sample first to see if there are any fibers or bloodstains, and then check the rubber debris on the wheels." He squatted down and looked at the wheel of the handcart. He saw a small amount of brown mud on the edge of the wheel, with a thin blade of grass hanging on it—the same as the blade of grass in the grass under the west wall.

“Look at the mud on the wheels!” Yang Sen pointed to the mud. “It’s the same brown mud as the mud at the gap in the wall, and this blade of grass must have been brought in from the bushes outside the wall!”

Yang Lin took out the evidence box, used tweezers to remove the grass leaves, and used a knife to scrape off the brown mud from the wheel, putting them into different evidence bags: "Now there is more and more evidence. The handcart, wheel tracks, brown mud, grass leaves, and fibers can all prove that the suspect used this handcart to enter the logistics park through the gap in the west wall and transfer the body to warehouse number 13."

The two then tested the size of the handcart's wheels, which perfectly matched the marks in the passage. The rubber fragments on the wheels also matched the composition of the rubber friction marks at the edges of the marks. "We can confirm that this handcart is the tool the suspect used to move the body!" Yang Lin stood up, dusted off his hands, and said, "We'll send these samples back to the branch's technical department now so they can identify them as soon as possible."

At 8 p.m., Yang Lin and Yang Sen returned to the Criminal Investigation Detachment's Technical Section with all the samples. Section Chief Zhang was already waiting in the lab: "I've looked at all the samples you sent. We'll start with fiber identification, then analyze the soil composition. The comparison of the tire rubber fragments might take a while, but we'll definitely have the results tonight."

Yang Lin handed the fiber sample to Lao Zhang: "Section Chief Zhang, this fiber is the same color as the fiber found next to the body in warehouse number 13. Please check if the composition is the same. If we can determine the source, such as a certain brand of work pants, we can narrow down the scope of the investigation."

Old Zhang placed the fibers under the microscope and adjusted the focus: "From preliminary observation, both fibers are made of cotton-polyester blend, with 70% cotton and 30% polyester. This material is very common in work pants in factories or logistics parks—didn't you mention a former porter named Chen at the logistics park? You can check if the work pants Chen wore before were made of this material. Also, the suspicious person wearing blue work clothes and carrying a black cloth bag, his work pants may also be made of this material."

Yang Sen added, "We also found brown soil at the gap in the wall, which is the same as the soil on the wheelbarrow wheels. Can you take a look at the composition of the soil and determine its source? If we can find the specific source of the soil, we might be able to find the suspect's hiding place."

Old Zhang took the soil sample and put it into the composition analyzer: "The soil contains a lot of gravel and humus, as well as a small amount of coal slag. Soil with this composition is very common near abandoned factories in the suburbs. There is an abandoned fertilizer plant 3 kilometers south of the South Suburb Logistics Park. The soil composition there is very similar to this. You can go there to investigate."

At this point, the comparison results of the rubber fragments from the wheel also came out—the rubber fragments on the handcart wheel were completely consistent with the rubber friction marks on the edge of the wheel tracks in the passage between warehouses 14 and 13, further confirming that the handcart was the tool used to move the body.

"Great!" Yang Lin said excitedly. "Now we know that the suspect was likely wearing cotton-polyester blend work pants, came from the direction of the abandoned fertilizer plant in the suburbs, entered the logistics park through the gap in the west wall, and used a handcart in the freight area to transfer the body to warehouse number 13. Moreover, the suspect was very familiar with the environment of the logistics park, knew that warehouse number 13 was vacant and the surveillance was not working, and also knew the location of the handcart."

Yang Sen nodded, took out his notebook, and jotted down the clues: "Combined with the previous clues, the suspect is about 170 centimeters tall, wears size 42 work shoes, and smokes 'Hongtashan' cigarettes. Now we have a few more characteristics: wearing cotton-polyester blend work pants, possibly from the vicinity of the abandoned fertilizer plant, and familiar with the logistics park environment. These characteristics together narrow down the scope of our investigation considerably—we can focus our investigation on current and former employees of the logistics park, especially those living near the abandoned fertilizer plant, and those who have recently used handcarts in the logistics park's freight area." (End of Chapter)