The veteran detective took another sip of the water mixed with sand, then spat twice, saying, "The water mixed with sand tastes a bit salty and astringent…"
"That's right, salty and astringent," Lin Chen snapped his fingers with a smile. He pointed to a pile of sand in the distance and said, "Sand seems ordinary, but there are different types."
"There's Mountain Sand, River Sand, and Sea Sand. Although all are sand, Sea Sand cannot be used as construction material."
"Sea Sand contains a high salt content and excess chloride ions, which make it highly corrosive. It not only damages concrete itself but also destroys the passive film on steel reinforcements, causing corrosion. Buildings made with Sea Sand last only half as long as normal structures. Many buildings with exposed steel and peeling facades are due to the use of Sea Sand."
"Even though Sea Sand is unsuitable for construction, unscrupulous merchants and developers still use it because it's cheap and boosts their profits."
Lin Chen turned his gaze to the landlord. "The sand used for your rooftop addition is Sea Sand."
Before the landlord could respond, Lin Chen looked at Bao Qingshan. "And the sand embedded in the tread of your leather shoes is Sea Sand as well. Although Tianhai City has 'Hai' (meaning sea) in its name, it's not a coastal city, so Sea Sand isn't common here."
"Bao Qingshan, tell me why Sea Sand appeared on the rooftop and also on the soles of your shoes?"
Bao Qingshan stared anxiously at the photo of the shoe sole on Lin Chen's phone. "Officer, the sand on my shoe soles is just ordinary sand. Why do you say it's Sea Sand? It's just sand."
"That's simple," Lin Chen said. "Take out the sand from your shoe soles and compare it with the sand on the rooftop through testing. That will settle it."
"Damn, they actually sold me Sea Sand? That's despicable," the landlord muttered angrily.
No one paid attention to the landlord's curses. Bao Qingshan clenched his teeth and said, "I haven't worn those shoes in a long time. Even if the sand inside is Sea Sand, it could have gotten there somewhere else before. You can't conclude I came here just based on this."
"Yeah," Bao Qingshan's wife chimed in, "We used to live near a construction site, and we walked past it every day. Maybe the builders were using Sea Sand."
Facing the couple's renewed denial, Lin Chen smiled and calmly asked Bao Qingshan, "Do you smoke?"
"I used to, but I quit," Bao Qingshan answered.
"Have you relapsed recently?" Lin Chen asked again.
"No, I haven't smoked recently. I'm determined to quit."
Miao Yunfei looked at Lin Chen's composed face and thought, First the shoe soles, then the sand, and now smoking… his leaps in logic are a bit much.
Lin Chen looked at everyone and said, "Come with me."
They all followed Lin Chen to the other side of the rooftop. Lin Chen pointed to a slightly gray-black spot on the railing and said, "This is the mark left by a recently extinguished cigarette. It's fresh — clearly made within the last few days."
Lin Chen asked the construction workers who had been working on the addition, "Do any of you smoke?"
The workers all shook their heads, saying they didn't smoke. The landlord vouched for them, "Officer, none of them smoke; I can prove that."
"Good." Lin Chen looked at Bao Qingshan. "The deceased didn't smoke, these workers don't smoke, and the landlord doesn't…"
Before Lin Chen finished, Bao Qingshan interrupted, "Are you saying that cigarette butt was left by me? Come on, officer, there are so many residents in this building. Why isn't it theirs and why is it mine?"
"First, the rooftop is under construction and very messy these days. Regular residents generally wouldn't come up here to smoke."
"Second, and most importantly, I found this down on the ground beneath that cigarette butt."
Lin Chen pulled a sealed plastic bag from his pocket, inside which was a crushed cigarette butt.
"When I came to the rooftop yesterday, I saw the cigarette burn mark on the railing. Someone smoked here, but I couldn't find the cigarette butt on the rooftop — I thought it was thrown downstairs."
"So on my way down, I went around this side because it's close to the neighboring building and the alley is narrow. Very few people walk down here. I found this cigarette butt in the alley. You said you haven't smoked recently, right? We can test the DNA on this cigarette and compare it with yours to find out."
Bao Qingshan's face instantly froze, his eyes momentarily losing focus.
Zhang Tian'ai looked at the cigarette in the sealed bag and suddenly recalled, "I remember yesterday after we left the building, you told me and Xia Miaoyan to wait outside a while, then you left. You were going to look for this cigarette butt, weren't you?"
"That's right," Lin Chen said. "You told me earlier that the workers said none of them went to the rooftop during the day. So the cigarette must have been smoked there at night. The rooftop is so messy, who would come up to smoke at night for fun?"
Lin Chen looked at Bao Qingshan. "You don't need to say anything now. Let me reason through your crime process, how you managed to have an alibi while still killing the victim."
This book is provided by FunNovel Novel Book | Fan Fiction Novel [Beautiful Free Novel Book]