The killer thought he had committed the perfect crime, attempting to conceal all evidence with fire and deceive everyone.
But in reality, flaws had already emerged.
He completely underestimated and failed to understand the profession of forensic science.
The job of forensic scientists is to make the dead 'speak'!
...
After surveying the scene and collecting all usable evidence, Han Fei led the officers back to the police station.
Staying at the scene and stubbornly searching wasn't the solution, as it had been burned beyond recognition, leaving no traces of the killer. Remaining there would only be a waste of time.
To catch the killer, they could only rely on surveillance footage.
Back at the station, the officers began reviewing the footage.
The fire had occurred not long ago, so they needed to check the surveillance from the few hours before the incident.
Especially the footage from outside the restroom.
The killer either killed the victim first and then carried the body into the restroom,
Or simply committed the murder in the restroom and then set the fire to cover up the evidence.
But regardless of which scenario, there would certainly be clues left behind.
While the officers were reviewing the footage, the forensic team was conducting the autopsy.
Half an hour later.
The forensic examiner made progress.
"Captain Han, here's the preliminary autopsy report. The victim has two fatal stab wounds on the left side of the back of the neck. The cause of death was massive blood loss from a ruptured artery. The killer is likely left-handed. Judging from the shape of the wound, the murder weapon was a very common fruit knife. The blade was inserted diagonally downward into the back of the victim's neck, which suggests the killer held the knife in reverse, with the blade on the pinky finger side rather than the thumb side. The stabbing posture was probably... like this."
The forensic examiner demonstrated the killer's stabbing posture to Han Fei.
"So if the knife was angled downward into the back of the victim's neck, does that mean the killer was taller than the victim?"
The examiner nodded, "Yes, the victim was 173 cm tall. The killer should be at least 180 cm or taller, otherwise this angle of entry would be unlikely. However, we can't rule out the possibility that the killer deliberately created this angle of entry."
"I see. Continue with the autopsy and see if you can find any more clues," Han Fei placed the autopsy report on the table and resumed watching the surveillance footage.
From the autopsy report, they obtained two clues.
First, the killer might be left-handed.
Second, the killer's height should be 180 cm or above.
Of course, they couldn't rule out the possibility that the killer deliberately misled the police.
That's why the forensic examiner used words like 'should' and 'likely' when discussing these points.
Han Fei had been involved in many major cases and was very experienced.
He had encountered many cunning killers before.
There have been instances where right-handed killers used their left hand to mislead the police.
Just then, Xu Mo pointed at the computer screen and spoke up.
"Rewind the footage two seconds, Captain. This janitor entering the restroom looks suspicious. Janitors are usually older men or women, but judging by this person's gait, they're clearly young. The body shape suggests it's a man, and he's wearing a mask to cover his face. He's also keeping his head down, probably to avoid the cameras."
Following Xu Mo's finger, Han Fei saw a janitor pushing a cleaning cart in the surveillance footage.
"This person is indeed suspicious, and there was also a burned cleaning cart in the restroom..." Han Fei muttered, staring at the screen.
He called out to Chen Ke.
"Chen Ke, call the person in charge at the TV station building and ask who the janitor for the 13th floor is. Is it a young man?"
Chen Ke immediately took out his phone and made the call.
Shortly after, he put down the phone.
"The person in charge there checked and said the janitor for the 13th floor is a middle-aged woman named Ma Huifen, 54 years old. He also said all the janitors in the entire TV station building are middle-aged women, no young people."
Hearing this, Han Fei and Xu Mo exchanged glances.
The 13th floor janitor was a middle-aged woman.
All janitors in the entire TV station building were middle-aged women, with no young people.
So the identity of the young male janitor wearing a mask and hiding his face in the surveillance footage became apparent.
He was almost certainly the killer!
He had deliberately disguised himself as a janitor to get in.
Wearing a mask and walking with his head down was also to prevent being caught on camera.
The surveillance footage continued to play.
The suspicious janitor came out of the restroom one minute after entering.
When he came out, he wasn't pushing the cleaning cart.
Moreover, his pace was noticeably faster than before.
In just three seconds, he disappeared from the surveillance footage outside the restroom.
Shortly after he left, the fire broke out in the restroom.
Later, people tried to put out the fire, but it was too intense to extinguish.
It's worth mentioning that Han Fei and Xu Mo also saw a scene in the surveillance footage.
The flames in the restroom suddenly expanded, bursting out of the door and burning several people who were trying to fight the fire.
After that, someone took out their phone and started dialing for help.
The time shown was 5:43 PM.
This was exactly when the police station received the report.
Although the surveillance had no sound, judging from the sudden burst of flames, this should be the explosion mentioned by the caller.
The initial analysis suggested that this was an explosion caused by the fire igniting methane gas.
The caller mistook the explosion for a terrorist attack and immediately called the police.
Seeing this, Han Fei immediately confirmed.
The arsonist was this suspicious janitor!
Han Fei quickly switched to another camera to continue tracking this suspicious janitor.
He wanted to see where he went after leaving the restroom.
The surveillance footage showed:
After leaving the restroom, this suspicious janitor went to the elevator and left the 13th floor.
During this time, he consistently kept his head down while walking, even after entering the elevator.
Combined with his mask and janitor's hat,
This meant the surveillance cameras never captured a clear view of his face.
Han Fei then retrieved the surveillance footage from the lobby on the first floor of the TV station building.
After taking the elevator to the first floor, this janitor directly left the TV station building through the main entrance.
"The surveillance inside the building is no longer useful. We need to check the external cameras to know where he went after leaving the TV station building," Han Fei paused the footage. "This killer has strong anti-detection skills."
Then, Han Fei called Chen Ke over.
"Chen Ke, go again and get all the surveillance footage from around the TV station building. Continue tracking this person!"
Xu Mo, recalling something, spoke up.
"There's a square right outside the main entrance of the TV station building. I've seen it, and there isn't a single surveillance camera in the square. Checking surveillance will be too slow. This person has some anti-detection skills; he's been deliberately avoiding cameras capturing his face. The surveillance method might not be effective. Why don't we try investigating from the victim's social relationships, see if they had any enemies?"