A Clue?

 "What's the matter?" Zhou Qiang quickly responded to Su Xuan's words. "Chen Canjun already has a solid alibi. Even if there are some ethical concerns, he truly didn't have the chance to commit murder. You're not still suspecting him, are you?"

In reality, aside from Su Xuan's search for evidence against Chen Canjun, Zhou Qiang had been trying to find evidence against the other two people involved, but they had come up empty-handed.

The strange part of this case centered around Chen Jianguo. According to the video, it appeared that he accidentally fell into the river. However, there were fingerprints on his body, and after forensic examination, it was clear that he had been tightly restrained before his death. The person who had held onto his limbs had used a lot of force, leaving deep marks even after his death.