Everyone behind the door did not go up to the rooftop. Including Qin Yong, they all looked at Lu Chuan eagerly.
"Is it possible that we guessed wrong?"
The rooftop is only two to three hundred square meters in size, and you can basically see it clearly at a glance.
If there are traces of dragging, logically speaking, it is most likely to start from the door and extend to the edge of the rooftop.
However, there is nothing in front of everyone now.
"Wait a minute, didn't Lao Liu take the spectrometer to see if it has any effect."
Everyone's whispers did not affect Lu Chuan.
That's what solving crimes is all about, and of course mistakes are possible.
But you can’t stop guessing or thinking just because you made a mistake.
What's more, Lu Chuan was originally mentally prepared for this.
If there are no drag marks on the rooftop, there are basically only two possibilities.
First, there are no drag marks at all. The friction on Zhou Yang's shoes is caused by other reasons, but Lu Chuan has not found the reason yet.
Second, the drag marks do exist, but they were cleaned up by the murderer, so they are not visible to the naked eye.
But it doesn’t matter, just because it can’t be seen with the naked eye, doesn’t mean it can’t be seen with the instrument either.
The black surface left by rubber dragging is easy to clean or wipe off, but the material left behind cannot be completely disappeared.
Through a spectrometer with a special frequency band, it can be seen clearly.
Soon, the portable variable frequency spectrometer was brought up.
"Xiao Lu, the spectrometer is here."
"Okay, just hand it to me."
Lu Chuan moved the pedal and took the spectrometer from Liu Guodong's hand .
Power on and warm up.
The principle of emitting light is similar to that of a halogen lamp. It needs to be warmed up before it can work.
After a while, Lu Chuan adjusted the corresponding light wave frequency band, and a beam of faint light shone out.
A magical scene happened in front of everyone.
There was nothing on the ground, but a series of traces extending from the door to the rooftop were looming.
Wherever the beam of light shines, black traces appear.
“There are really traces!”
After confirming the existence of dragging traces, we can basically confirm that Zhou Yang committed suicide.
The nature of the case is determined, and the mentality of the investigators is completely different.
When I first discovered the body, I basically followed the normal flow. After all, no one knew at that time whether Zhou Yang committed suicide or was murdered.
Once the homicide is confirmed, the criminal investigation detachment will set up a special task force and report the case. It is a murder case that must be solved.
At this time, everyone’s mental tension was completely different from just now.
"Sun Jun, send someone to investigate all the surveillance systems in the building."
"Ren Qiang, conduct a thorough investigation of Zhou Yang's interpersonal relationships, and find out what happened to Zhou Yang from last night to this morning. Who has Yang contacted? Check the phone records to see who has contacted him."
"Yes!"
Once the first crime scene was discovered, it was left to the immediate investigation, and the others would naturally have other things to do.
Liu Guodong also began to put on equipment, including shoe covers, gloves and even goggles, ready to survey the scene with Lu Chuan.
"Master, give me the machine. I will adjust the frequency band and see if I can find the murderer's footprints."
At any crime scene, you are not afraid of intentional damage by the murderer. What you are most afraid of is what the murderer is. Neither moved.
For example, on this rooftop, the murderer deliberately erased the traces left by dragging Zhou Yang, but this also shows that the murderer stayed on the rooftop for a long time.
In the process of cleaning up traces, more traces of contact with the scene will definitely be left behind.
Like more footprints. But if the murderer left immediately after throwing Zhou Yang downstairs, there would be fewer footprints and the possibility of the police extracting samples would be smaller.
The variable frequency spectrum adjusted the frequency again, and the traces of dragging gradually disappeared, and instead a bunch of dense footprints appeared.
“So many footprints?”
The footprints are superimposed, rubbed, and many traces are unclear, but because there are enough, there are always one or two groups of footprints that are relatively clear.
"Master, give me the camera."
Lu Chuan was also very excited. With so many footprints, it would be easier to find a few clear sets and do footprint analysis.
"Master, the footprints are almost ready. Come in and let's see if we can wipe off the fingerprints."
Lu Chuan stood up and stopped stepping on his feet.
The footprints at the scene have been extracted, and the development under the frequency conversion spectrum has been recorded, so we can proceed to the next step.
"The edge of the rooftop is about fifty centimeters high. If the opponent wants to throw Zhou Yang down, he may hit the edge of the rooftop."
Lu Chuan nodded in agreement and began to wipe his fingerprints.
Under outdoor conditions, many light-based fingerprint collection methods are not particularly easy to use.
Fingerprints are not like footprints. The texture of footprints is rough. A single mark may be thicker than a fingerprint.
Therefore, in terms of detail presentation, fingerprint collection is more delicate than footprint collection, and is also more difficult and detailed.
Liu Guodong is not a novice in this area, of course there is no problem.
“I just hope that the other party will be more careless and not wearing gloves...”
Of course Lu Chuan also hopes that the other party will not wear gloves, but this is unlikely.
The murderer is very meticulous and can think of erasing drag marks. He will not wear gloves when killing people and leave fingerprints.
Security room on the first floor.
Sun Jun’s monitoring and review was not going well.
“The monitoring system has been broken for a week and has not been repaired.”
There is no monitoring system and there is such a large flow of people in the building. How can we investigate?
"Well, when I just entered the apartment, didn't all the owners in the building have to swipe their cards to enter? Can you export the card swiping records of all the people from last night to 8:30 this morning?"
"That's no problem. Just wait for me and I'll get it out right away."
The door of Haizhou International Apartment uses a magnetic card access system, and each magnetic card is bound to the room.
Although some cards may be given directly by the owner to the tenant, and cannot directly lock the identity of the person, but once the house is locked, you can just check it.
Soon, Sun Jun's group got the relevant data.
“Let’s group them into groups. There are one hundred and eighty-six people in total. Two people work in pairs. Be sure to find out the basic information of all the people today.”
This kind of thing is basically no different from finding a needle in a haystack.
No one knows whether the person who killed Zhou Yang is the owner or tenant here.
Is it possible that an outsider did it? The security of the building is not watertight.
Don’t swipe your card, just skip the gate, and the security will not care.
But that’s how it is to solve a case. After investigation, there is no guarantee that there will be clues.
But if you don’t investigate, there will definitely be no clues.
Zhou Yang’s parents also came over to the single apartment where Zhou Yang lived.
Zhang Huizai and the two of them learned about Zhou Yang's situation.
"Teacher Zhou, who are Zhou Yang's friends and who he is close to, can you tell me?"
Zhou Yang's parents were sitting on the sofa, holding each other in their arms. Son's photo.
The tears... have long since dried up. (End of this chapter)