Luminol reagent is the most commonly used blood identification product for criminal investigation on-site investigation.
The proteins contained in the blood cannot be washed away with ordinary water.
At the same time, traces of the large amount of iron ions contained in it cannot be eliminated by simple cleaning. Luminol reagent can reduce blood stains into fluorescent traces through chemical reactions.
Of course, luminol reagent will produce chemical reactions on all blood, and it cannot be determined that it must be human blood through the luminol reagent test.
So, in blood identification, after confirming the presence of blood, the type of blood will also be determined.
Even if the scene is like this, there is a high probability that it is the traces left by human blood. After all, no one can kill chickens and fish to cause this phenomenon.
But after returning to the current investigation laboratory, Lu Chuan and others still had to identify and analyze the type of blood.
Of course, based on the current situation at the scene, it can be determined that it is human blood.
The identification is only a necessary judicial procedure and does not affect the subsequent steps and speculations of the current investigation.
Lu Chuan waved his hand and made a circle, meaning that the bathroom was not the scene where the body was dismembered, but the scene where the murderer disposed of the body.
"The murderer probably washed away some debris of limbs through the sewer here."
"The fat debris and organ fragments found in the sewer blocked the sewer, so half a finger was left. ”
In the living room, Yang Sen is collecting fingerprints.
It is daytime, and the ultraviolet fingerprint light is not very efficient at detecting fingerprints, but it can distinguish whether there are fingerprints.
After the fingerprints were determined, Yang Sen collected the fingerprints through the powder method.
Lao Bai collected some hair from the bed in the bedroom.
According to the information provided by the landlord, the room was only rented to Yang Qianqian.
So, the traces of life left here should belong to Yang Qianqian.
After the collection is returned, the DNA extracted from the hair and fingers can be compared to determine whether the deceased is Yang Qianqian.
While the current survey side was carrying out its work in an orderly manner, the second operation team began to visit the neighbors.
"There is a girl living next to me. She is pretty and very tall, but she doesn't socialize with us very much. She has been living here for two or three years."
"Have I ever seen anyone there before? Come next door? "
The house Yang Qianqian rents has two floors and three floors. Her room is in the middle. In addition to her room, there are two neighbors on the left and right.
There is no one in room 601 on the right, and the management is contacting us.
A family of five lives in room 603 on the left, and the hostess's parents are at home.
Zhang Hui was questioning the two people.
“I didn’t pay much attention to this. The girl next door gets up late in the morning. Usually she doesn’t get up until the afternoon, but she comes back late at night.”
“When the girl comes back we I usually go to bed, so I don’t pay much attention to her.”
“But the girl is quite polite. We meet her sometimes on weekends and she often greets us.”
“Recently. Have you found any suspicious persons in the past few days? ”
"No... the security of our community is pretty good, the security guards are on patrol."
"It seems that no strangers were found in and out of the building."
"But in this city It’s different here than in the countryside. We don’t know each other very well.”
“Have you heard anything in the past few days?”
“Nothing?” br>
"Nothing happened there... Oh... By the way, their family seemed to make dumplings a lot in the past few days."
"Oh? How did Auntie know that their family made dumplings?"
"There was the sound of the meat grinder, buzzing and non-stop..."
The kitchen of the room where the crime occurred.
Liu Guodong found a meat grinder in the closet.
"Xiao Lu, come here."
Although the meat grinder was quite clean, Lu Chuan still discovered some details. "There are blood stains on the blade and handle."
After that, I sprayed the luminol reagent...
The entire meat grinder fluoresced. .
Liu Guodong sighed: "Put it away."
Then, the two conducted a detailed inspection of the kitchen.
"Master, there is blood splatter here!"
There are blood stains sprayed at high speed on the kitchen wall, and there are blood stains on the display window.
It’s just that the other party cleaned it up very carefully and wiped it all off.
But under the cupboard, there were still blood stains that had not been cleaned up.
“This!”
Then, Lu Chuan found a bloody ax in the gap behind the refrigerator.
The wooden handle of the entire ax head is dark red, and there are fine bone residues where it is connected to the ax head.
“Is this a dismemberment tool?”
Liu Guodong nodded, picked up the axe, and looked at it. There were already slight curls and small gaps on the blade surface.
“Bought new.”
But on the rear section of the wooden handle of the axe, you can clearly see the fresh wood texture, which is light yellow, and it was obviously just bought.
After putting the ax into the evidence bag, the two continued their investigation.
After a while, a package of curled black plastic was found inside the cupboard.
After Lu Chuan took it out, the nauseating smell of blood suddenly came out.
After unfolding the black plastic, there were still some undried blood stains on it, probably because the plastic was curled up and not evaporated.
At the same time, a chopping board stained with brown blood was also found under the cabinet.
There are obvious marks of ax chops on it.
“The murderer should have put the body on a plastic sheet, then placed it on a chopping board and used an ax to dismember it.”
"Then he used a meat grinder to crush the flesh and blood and washed it away in the sewer."
Liu Guodong nodded and agreed with Lu Chuan's analysis. The murderer obviously did not want to hide these things.
"But one thing, where are the bones?"
Liu Guodong pointed to the meat grinder next to him: "This thing can break down the meat, but it is impossible to cut all the bones. Grind it into crumbs and wash it away in the sewer."
Human bones are much harder than most people imagine.
The specific data is difficult to describe, but if the hardness of steel is compared to 9, then the hardness of human bones is between 4 and 5.
The hardness of relatively hard parts such as teeth and skulls may reach 6 or 7.
Liu Guodong has handled several corpse dismemberment cases before, but in none of them did he find that the murderer could use any convenient equipment to finely chop human bones.
Of course Lu Chuan also knew this.
Compared to Liu Guodong, he has the skills of skeletal identification and knows more about human skeleton.
However, there is more than just physical methods to wear down human bones.
Sometimes it is easier to wear away human bones using some chemical methods.
In terms of chemical composition, the main component of human bones is calcium carbonate.
Soaking bones in acidic substances can soften the bones in a short time.
After that, some physical methods can be used to break the bones into fine pieces.
However, in several cases that Lu Chuan had experienced, the murderer had not been found to have used this method, and no suspected chemical substances were found at the crime scene. (End of this chapter)