Diary of a Criminal Investigator-Chapter 300: Searching for a Needle in the Ocean
None of the people behind the door, including Qin Yong, went up to the rooftop. They all looked eagerly at Lu Chuan.
"Is it possible that we guessed wrong?"
The rooftop is only two or three hundred square meters in size, and you can basically see everything at a glance.
If there are drag marks, logically speaking, it would most likely start from the door and extend to the edge of the rooftop.
But now, everyone sees nothing in front of them.
"Let’s wait a moment. Didn’t Old Liu take the spectrometer? Let’s see if it works."
The whispers of the others didn’t distract Lu Chuan.
Solving a case is just like this; making mistakes is, of course, possible.
But you can’t refrain from guessing or thinking just because you might be wrong.
Moreover, Lu Chuan was originally somewhat mentally prepared for this possibility.
If there are no drag marks on the rooftop, there are basically two possibilities.
First, there are no drag marks at all, and the friction on Zhou Yang’s shoes was caused by something else, but Lu Chuan hasn’t found the reason yet.
Second, the drag marks did exist but were cleaned by the culprit, making them invisible to the naked eye.
But that’s okay; the fact that they are invisible to the naked eye doesn’t mean they are invisible to instruments.
The traces left by rubber dragging are easy to wash or wipe off on the surface, but the substances left behind cannot completely disappear.
With a special frequency spectrometer, these traces can be seen clearly.
Soon, a portable frequency-changing spectrometer was brought up.
"Lu, the spectrometer is here."
"Okay, just hand it over to me."
Lu Chuan adjusted the foot pedal and took the spectrometer from Liu Guodong’s hand.
Turned it on for preheating.
The principle of this gadget’s illumination is somewhat similar to that of a halogen lamp; it needs to preheat before it can work.
A moment later, Lu Chuan adjusted the corresponding light wave frequency, and a faint light shone out.
A magical scene unfolded before everyone.
On the ground where there had been nothing, a series of marks extending from the doorway to the rooftop gradually appeared.
Wherever the beam of light shone, black traces appeared.
"There really are marks!"
With the drag marks confirmed, it was basically certain that Zhou Yang was murdered.
With the nature of the case confirmed, the mindset of the investigators completely changed.
When the body was first discovered, they were generally following routine procedures, as no one knew at that time whether Zhou Yang had committed suicide or been murdered.
But once murder was confirmed, the Criminal Investigation Team would set up a special task force, and the case would be reported as a must-solve homicide.
At this point, everyone’s level of tension was completely different from before.
"Sun Jun, send someone to review all the surveillance of the building."
"Ren Qiang, conduct a thorough investigation of Zhou Yang’s interpersonal relationships; find out who he interacted with from last night to this morning, check phone records, and see who contacted him."
"Yes!" 𝒻𝘳𝘦𝘦𝘸ℯ𝒷𝘯𝘰𝑣ℯ𝑙.𝘤𝑜𝘮
Now that the first crime scene was discovered, it was handed over to Crime Scene Investigation, and the others naturally had other tasks to attend to.
Liu Guodong also began donning his equipment—shoe covers, gloves, even goggles—fully equipped, ready to work with Lu Chuan to inspect the scene.
"Master, give me the machine; I’ll adjust the frequency to see if we can find the culprit’s footprints."
Any crime scene, it’s not scary if the culprit intentionally destroys, but the most frightening is when the perpetrator doesn’t touch anything.
For example, at this rooftop, the culprit deliberately erased the traces left by dragging Zhou Yang, but it also indicates that the culprit stayed on the rooftop for a longer time.
During the process of cleaning the traces, more contact traces with the scene would inevitably be left behind.
Such as more footprints.
But if the culprit left directly after throwing Zhou Yang off the building, there would be fewer footprints, and the possibility of the police extracting samples would be lower.
The frequency of the spectrometer was adjusted again, the drag marks gradually disappeared, and a bunch of dense footprints appeared.
"So many footprints?"
The footprints were overlapping, some were scuffed, and many traces were unclear. However, due to their quantity, there were always one or two sets of footprints that were relatively clear.
"Master, give me the camera."
Lu Chuan was also very excited; with so many footprints, finding a few clear ones makes footprint analysis relatively easy.
"Master, the footprints are almost done. Come in, let’s see if we can find any fingerprints."
Lu Chuan stood up and didn’t step on the pedal anymore.
The footprints at the scene had been extracted, and the images captured under the changing frequency of the spectrometer had been recorded, allowing them to proceed to the next step.
"The edge of the rooftop, there’s about fifty centimeters of height here; the other party might have touched the edge of the rooftop when throwing Zhou Yang off."
Lu Chuan nodded in agreement and began wiping for fingerprints.
In outdoor conditions, many lighting-based fingerprint collection methods are not particularly effective.
Fingerprints, unlike footprints, have finer patterns, and a single print might be smaller than a footprint.
Therefore, in terms of detail presentation, fingerprint collection is generally more precise than footprint collection, requiring more finesse and effort.
Liu Guodong was not a novice in this regard, so of course there was no problem.
"Just hope the other party was a bit careless and didn’t wear gloves, that would be best..."
Lu Chuan also hoped the other party hadn’t worn gloves, though it wasn’t very likely.
The culprit was meticulous enough to erase the drag marks, so it was unlikely they would commit murder without gloves, leaving behind fingerprints.
First-floor security room.
Sun Jun was having trouble with the video surveillance review.
"The surveillance has been broken for a week and hasn’t been repaired yet."
Without video surveillance, and with such a large flow of people in the building, how could they investigate?
"Here’s the thing. When I entered the apartment, I saw that the owners needed to swipe a card to enter, right? Can you export all the card swipe records from last night until 8:30 this morning?"
"That’s no problem. Hold on a moment, I can get it out right away."
The access control at Haizhou International Apartments uses a magnetic card system, with each card linked to a corresponding room.
Although some cards might be given directly by the owner to tenants, not allowing direct identification of individuals, you could trace it by locking down the room.
Soon, Sun Jun’s team obtained the relevant data.
"Let’s split up. There are 186 entries in total; pair up, and make sure to get a basic understanding of everyone’s information today."
Such tasks are pretty much like searching for a needle in a haystack.
No one knows whether the person who killed Zhou Yang was an owner here or a tenant.
Could it have been an outsider? Building security wasn’t airtight.
You could skip the turnstile without swiping a card, and the security wouldn’t stop you.
That’s how solving cases goes—you can’t guarantee you’ll find a lead if you investigate.
But if you don’t investigate, you definitely won’t find any lead.
The single apartment Zhou Yang lived in, his parents also came by.
Zhang Hui was talking to them to learn about Zhou Yang’s situation.
"Teacher Zhou, who were Zhou Yang’s friends usually? Who was he close to? Could you talk about it?"
Zhou Yang’s parents sat on the sofa, hugging a photo of their son.
Their tears... had long dried up.
