Diary of a Criminal Investigator

Rinsing blood with clear water can only clean the platelets and cannot completely remove the DNA substances or protein substances present in the blood.

To put it simply, rinsing blood with clear water only washes away the color, making it seem like there’s no blood on the surface, but certain substances in the blood still remain on the carrier.

To completely remove blood stains, you need to use some special cleaning substances.

This special cleaning agent is not single, but a mixed cleaning agent.

In most cases, ordinary detergent mixed with protease, and some clear water, can fairly thoroughly remove the residual traces of blood.

The reason for adding protease is that the blood contains a large amount of protein substances, which is how we can detect DNA information in the blood.

Using protease can effectively decompose the protein substances in the blood.

As for using detergent, it can dissolve grease, allowing the damaged protein substances to dissolve in water and be washed away afterwards.

Of course, there are stricter requirements on the proportion of protease content, the amount of detergent, and the amount of clear water to completely clean up residual blood traces.

Ordinary people couldn’t possibly master this.

Obviously, the killer of Zhang Xiaotian and the other three did not have such skill reserves and just roughly treated the blood stains with clear water.

The pillowcase from one of the two pillows on the bed disappeared, possibly used by the perpetrator to wipe off the blood.

It should have been taken away by the perpetrator afterwards.

Besides this, Lu Chuan also found some bloody footprints at the scene.

"The killer is a woman?"

There were no footprints of the two murdered men in the coagulated blood, as they were lethally attacked, but there were footprints of the two murdered women.

It was relatively easy to identify; the two murdered women were not wearing socks or shoes, so the footprints left were barefoot.

Based on the current findings, it can be analyzed that the killer should have entered the room while the four were asleep, initially targeting the two men, directly severing the carotid arteries, to kill them with one cut.

Subsequently, the two women might have been awakened by the assailant, leading to a struggle.

During the struggle, the killer stabbed the two female victims with a sharp knife.

Besides the barefoot prints, there was another set of prints left by the perpetrator in the pool of blood on the ground, which were unique and showed toes and heels—prints left by high heels.

That’s why Yang Sen concluded the killer is a woman.

However, based on the footprints, Lu Chuan provided the following physical characteristics of the assailant.

"Size 43 high heels, the perpetrator is approximately 1.78 meters tall and weighs around 70 kilograms."

If the perpetrator is indeed a woman, then she’s rather burly for a woman, as such height is quite rare among females.

Of course, it cannot be ruled out that the perpetrator is male and intentionally wore high heels to disguise actual footprints.

The subsequent work became meticulous, collecting samples of skin flakes, hair, and blood at the scene, among other information.

Some blood and skin tissue were also found under the nails of the two female victims.

It’s very likely that during the struggle, the female victims scratched the perpetrator’s skin.

"Crime of passion?"

Although the scene appeared bloody, the perpetrator left numerous flaws, whether in the blood stains wiped with clear water or the footprints in the blood pool, or the blood and skin flakes found under the nails of the female victims.

Any one of these clues could directly lock onto the suspect.

So Yang Sen believes it was a crime of passion. Otherwise, in a premeditated murder, the perpetrator would not leave so many conspicuous traces even if they just searched online for some information or watched a few movies.

"The probability of it being a crime of passion is higher, though it doesn’t rule out some planning by the perpetrator since, based on the murder timing, the perpetrator came over in the middle of the night."

"All four victims were asleep at that time; the perpetrator must have known the four victims beforehand, or at least knew the homeowner, as they couldn’t have had a direct conflict at that time node."

Of course, Lu Chuan said this, actually leaning towards the belief that the perpetrator committed a crime of passion.

Acting on a sudden impulse without prior planning, directly murdering them.

The two analyzed the case while collecting crime scene evidence in the cramped room.

After about three to four hours of busy work, the two came out, handed over with the forensic doctor, and then Wang Changjiang and Shen Yan entered.

"How is it?"

Qin Yong looked at Lu Chuan, inquiring about the crime scene investigation.

"We found a lot of clues. Based on the footprints left by the perpetrator, a preliminary analysis shows the opponent is approximately 1.78 meters tall and weighs around 70 kilograms."

"The perpetrator left high heel prints, but the shoe size is exceptionally large, a full size 43. I am more inclined to believe the perpetrator is male, deliberately wearing high heels for the crime."

"Height deviation is at most within two centimeters, and weight is probably within five kilograms."

"Captain Qin, it should be him. Shall we catch him?"

Standing next to Qin Yong, Zhang Hui got excited upon hearing Lu Chuan’s findings.

Based on external investigations, there is significant suspicion of Wang Junshan, who once lived with Zhang Xiaotian.

The personal information on Wang Junshan obtained by the Criminal Investigation Team also aligns well with Lu Chuan’s findings.

"Got a target?"

Lu Chuan knew immediately from Zhang Hui’s question that target suspects had been identified from the investigations.

Zhang Hui nodded: "Zhang Xiaotian was gay; the likely suspect could very well be his former live-in partner."

"Lu Chuan, have you found anything else?"

"Besides the footprints, the perpetrator likely left their blood at the scene. We have collected some samples, attempting to conduct DNA identification analysis. Furthermore, we found some blood and skin flakes in the nails of the two female deceased victims, possibly left by the assailant."

"Great, you guys should expedite the results. Zhang Hui, you go arrest the suspect first!"

"And Sun Jun, conduct a surveillance sweep of the surroundings to see if we can find suspects matching the given profile by Lu Chuan."

Although the surveillance in the incident building was already damaged, the surrounding road surveillance was intact. The perpetrator couldn’t have appeared out of nowhere, and since there was less pedestrian traffic at night, it might be possible to find traces.

This way, having identified a target suspect through field visits, matched with the evidence from Lu Chuan, and supplemented by surveillance, the case could be substantiated.

While the forensic doctor conducted examinations, the crime scene investigation team had already driven back to the Criminal Investigation Team.

DNA identification analysis could be completed within a day.

About two hours later, Zhang Hui also located Wang Junshan in another rental house.