Attending ex-girlfriend's wedding, arresting the groom's officer on the spot

The second investigation of the crime scene was done by Lu Chuan himself.

Lu Chuan conducted the entire on-site investigation to the highest standard within his ability, so a lot of things were tested.

There were quite a lot of inspection tables sent to the on-site investigation office of the Criminal Investigation Detachment. Yang Lin had already worked overtime for one night and it took him two days and one night to basically finish all these things.

Among the clues discovered are conventional clues such as fingerprints and footprints.

In addition, there were some undried bloodstains and some other sampling samples.

For example, Lu Chuan found some debris in the cracks in the bathroom floor and under the elbows of the kitchen sink and bathroom sink.

Because Wang Hong's DNA information and related fingerprint and footprint information had been collected in advance, some things could be ruled out more quickly.

"Old Lu, there are basically no clues about fingerprints and footprints. From what you collected, it seems that they are all from internet celebrities. The ones I can compare are basically all his, and there are no other strangers."

Normally speaking, even if the murderer stayed in the room for a short time and left few clues, there should be many fingerprints and footprints belonging to Wang Lili and Wang Hong in the room.

But now the fingerprints and footprints collected by Lu Chuan all belong to Wang Lili, which means that the murderer must have carefully cleaned up the scene after killing someone.

Of course, when Lu Chuan conducted the second investigation, it was a week after the incident and Wang Lili had lived in the room for two or three days.

However, with only two or three days, it is actually impossible to completely cover up all traces of Wang Lili's life.

It is obvious that the murderer did a more detailed cleaning.

"In addition, I checked the mop you brought back with the bloodstains you wiped back from the bathroom. The traces are basically the same. It can be confirmed that the mop was one of the tools used by the murderer to clean the scene. I also found some blood residue on it."

Yang Lin carefully inspected the mop that Lu Chuan brought back.

Although the murderer had cleaned the mop and washed it with clean water many times, and there was no unusual trace on the surface, there were still some iron ions and proteins in the blood.

Yang Lin just did some simple chemical experiments and was able to produce the results to prove it.

On the phone, Yang Lin continued to report his appraisal situation to Lu Chuan.

"The other party also cleaned the kitchen knife, and there were no traces of fingerprints or other residues on it."

Of course, it doesn’t mean that there are no fingerprints on it at all. There are Wang Hong’s fingerprints on it.

According to Wang, he found the kitchen knife on the refrigerator while cleaning.

So the first person who took the kitchen knife was Wang Hong, who did find fingerprints left on it, but this fingerprint was not a grip mark, but a mark of fingers pinching the handle.

On the other hand, if there really are no fingerprints left on the kitchen knife, then it can only mean that the internet celebrity is lying.

Because he must have committed fraud on the kitchen knife, and if there is no trace of him on it, it proves that Wang Hong cleaned the kitchen knife.

So it is normal to have Wang Hong's fingerprints on it. If her fingerprints are not there, there will be big problems.

Lu Chuan had actually anticipated this.

Since the murderer had cleaned the scene carefully, it was obviously unlikely that there would be any traces of him on the kitchen knife.

"Based on my experience, the curled blade on the kitchen knife should have broken when the murderer was chopping bones. Have you seen the molecular cells on it?" Lu Chuan asked.

This is a cutting-edge technology that has only emerged in recent years.

In fact, it is not widely used in the field of criminal investigation.

When Lu Chuan had just joined the Criminal Investigation Brigade, Qiangsheng Group donated 1 million yuan to the Administrative Brigade. Lu Chuan generously spent nearly 000 million yuan of it to purchase related equipment.

At that time, the detachment leader Qin Yong was very distressed.

After all, the total cost of other equipment was less than 1 million, but the small set of equipment that Lu Chuan purchased was not used very often, but it actually cost eight or nine million yuan.

But at that time, Qin Yong just felt distressed and didn't think much of it, after all, the money was donated by Qiangsheng Group. How Lu Chuan decided to spend it was of course his business, after all, they had already named him. It was to be used for the construction of the on-site investigation office laboratory.

But the money was not enough, so a lot of other equipment was added to the detachment.

Of course, it also improved the living conditions of many teams.

One of the more expensive ones is something called a flow cytometer.

This is an instrument that can rapidly analyze large numbers of cells.

It can reflect the cell cycle by detecting the quantitative level of cell surface markers.

Of course, this characteristic can also be used to mark cells from different people, and the functional states of different cells can be studied using fluorescence microscopes, confocal microscopes and other equipment.

Specific fiber technology combined with flow cytometer can mark different cells from different people.

For example, let’s analyze a kitchen knife.

Lu Chuan specifically instructed Yang Lin to conduct this kind of molecular and cellular testing on items such as the broom mop and kitchen knife that were confirmed to have been touched by the murderer.

The main reason is that if the murderer really took the kitchen knife and the mop, theoretically, the cells in his body would be in a state of metabolism all the time.

Even if the other party cleans it thoroughly, it is very likely that its cells will be left on the surface of the mop stick and the handle.

In addition, since it is impossible that the murderer was the only one who touched the kitchen knife, it is also possible that there were two people holding the mop, Wang Lili and Wang Hong.

Therefore, the most important thing is to distinguish the collected molecular cells first.

This is the role of flow cytometry, fluorescence microscopes, confocal microscopes and other equipment, which first mark and classify the cells before proceeding to the next more important task.

"That's what I want to say!"

Yang Lin's voice sounded slightly excited!
"According to the method you taught me earlier, I have extracted several different types of cells from the mop rod and the kitchen knife handle."

This step actually takes a lot of time. Labeling and analyzing cells is a very meticulous job because the composition and structure of human cells are basically the same.

It's just that because different people express DNA differently, there will be some subtle differences in the cells.

Of course, this most complicated step is not the most important, because Yang Lin’s goal is not just to separate the cells, but to obtain the DNA information material on them. (End of this chapter)