From what the pot-bellied man said, Yan Feifan learned that Mao Xiang, who held a grudge against him and Dr. Qiu, had copied his roommate Wang Tao's fingerprint with glue while he was asleep. This allowed him to easily get into the lab.
The man was actually quite clever. He had even done a crash course on some targeted hacking techniques.
He hacked into the computer connected to the lab's surveillance cameras, erased the footage of himself swapping the lab mice, and replaced it with footage from the same time the previous day.
However, to a professional hacker, his handiwork was as conspicuous as a bonfire in the dead of night.
After confirming the specific time of the crime, the investigators pulled the surveillance footage from within the neurosurgery building and several other nearby locations from the same time period. They quickly identified Mao Xiang as the suspect.
Once the police brought him in, he confessed to everything.
