Department of Psychology Forensic

Chapter 12 Preliminary Test of Bloodstains

Zhou Zheng stood on the inspection pedal, staring at the surroundings carefully. The effect of being able to check on the spot in person is far greater than that of looking at the case files. This allows him to experience all of this personally.

"There was such a large pool of blood at the scene, and there was no transfer of blood. There were a lot of splattered blood on the wall beside the deceased, and blood splattered on the ceiling of the living room, indicating that this is where the crime took place. The first scene." Zhou Zheng's voice sounded again, and as he inspected the scene, the eyes of many policemen protecting the scene also fell on him.

"The area of ​​the pool of blood is very large, and it has already covered up the blood splatter, wiping blood and bloody footprints that existed in the inner diameter, and it is still not dry. dead!"

While Zhou Zheng was speaking, he felt that the time was almost up, so he squatted down and took the thermometer from the deceased, and looked at it horizontally.

"The temperature in the rectum of the deceased was 29 degrees. Now that the season has just entered summer, the temperature last night exceeded 20 degrees. After death, the temperature in the rectum dropped by about 0.83 degrees per hour. The rate of decline in summer was almost 1.4 times that of spring and autumn. It can be roughly inferred that the time of death was 7 to 8 hours before the measurement, that is, between 22:30 and 23:30 last night."

Zhou Zheng quickly completed the mental calculation and estimated the time of death, then moved his position slightly, and stood on the other side of the pool of blood, that is, the right side of the deceased.

"This should be the place where the murderer killed the deceased. Although the traces under the feet were covered by pools of blood, there is a blank area on the wall behind here. Outside the blank area, you can see blood splatters, indicating that there is something here. Blocking the blood spurting from the carotid artery, combined with the severe trauma to the head of the deceased, it is preliminarily concluded that the deceased was stunned by a blunt instrument and then killed by a machete. However, the specific cause of death will not be confirmed until further anatomical identification .”

After Zhou Zheng finished speaking, he walked out from the pool of blood, centered on the corpse, and carefully inspected the scene outside.

Li Yanyan stared at Zhou Zheng in disbelief, her beautiful eyes widened. She had thought that Zhou Zheng was very powerful, but when she saw Zhou Zheng's analysis of the traces of the scene, she was still very shocked in her heart.

She has been in the forensic center for more than a year and has been working as Cui Jun's assistant. She has seen many corpses, and she can't even remember the number of times she appeared on the scene. ability.

This is not because she is not careful enough, but it is not so easy to find useful details in such a messy place on the scene. The details are constantly being speculated.

Cui Jun still stood where he was. He nodded silently, and the way he looked at Zhou Zheng also changed.

It doesn't look like an embroidered pillow!

Cui Jun didn't know that Wang Fan's case had something to do with Zhou Zheng, he was just a forensic doctor on duty, and he didn't ask anything other than work.

When Qin Wangde introduced Zhou Zheng yesterday, he thought that Zhou Zheng had used his connections to enter the forensic center for an internship. He was unwilling but still gave Qin Wangde face. Zhou Zheng stepped down to let the latter understand that the work of forensic medicine is not a child's play, and not everyone can come here to play.

But now, he has completely changed his view of Zhou Zheng. The ability shown by this new intern is already the work quality of a mature forensic assistant, even more careful than his assistant Yanyan.

Zhou Zheng entered the kitchen, looked around, and probably had an idea in his mind, and then turned around the inside of the room, and there were messy opened drawers in the bedroom.

"Where are the slippers of the dead?"

Zhou Zheng searched around the room with serious eyes, but found nothing, and went to the living room again, but still couldn't find anything.

"Slippers?" Cui Jun became puzzled. In the past, all he did was to examine the corpse, conduct a simple inspection of the scene, and return to the forensic center for autopsy. He had never found slippers at the scene.

"The dead man's leather shoes were taken off at the door without a single drop of blood on them. In addition, his clothes had not been changed, which indicated that he had just returned home when he was killed. The purpose of taking off his shoes was to change into slippers at home. Didn’t even see you taking off your shoes, could it be that they were taken by the murderer?” Zhou Zheng thought quickly, wondering, “Why did the murderer take away the slippers?”

"What are you looking for slippers for?" Li Yanyan's face was full of question marks. She could at least understand what Zhou Zheng was doing earlier, but now she couldn't understand it anymore, feeling like she couldn't keep up with her train of thought.

"There is a pair of slippers in the bathroom. I wonder if they are what you are looking for." The policeman protecting the scene said suddenly.

"Ok?"

Zhou Zheng immediately walked towards the bathroom again. When he was inspecting each room, he went to the bathroom, mainly to see if there were any blood stains on the washbasin, to confirm whether the murderer had disposed of the blood stains here, but there was nothing , and didn't think about the slippers.

Returning to the bathroom this time, thinking about looking for slippers, I suddenly saw a pair of high-grade canvas slippers next to the toilet at the door.

Zhou Zheng's heart tightened, he stood by the toilet, his eyes passed through the bathroom door, and he could vaguely see the entrance door at an oblique angle.

"I see."

Zhou Zheng's brain began to think quickly, constantly integrating the information found at the scene, and a thread gradually emerged in his heart. He carefully walked out with his slippers in his hand, and walked towards the inspection box.

"Master, are there any pre-test reagents?" Zhou Zheng asked.

"There are words on the bottles. The second one on the right is benzidine absolute ethanol saturated solution. Are you sure you can operate it?" Cui Jun's eyes on Zhou Zheng changed again.

"Master, you are watching!" Zhou Zheng didn't answer directly, but walked to the side of the inspection box, took out a piece of filter paper, rubbed it on the sole of the shoe, and then put the slippers into the transparent evidence bag inside.

"What do you mean by this operation?" Cui Jun stared at Zhou Zheng with great interest, becoming more and more satisfied with the latter's performance.

"Extract material from the sole of this slipper." Zhou Zheng replied.

"What is the purpose of doing this?" Cui Jun asked.

"The benzidine reagent has a great destructive effect on blood stains. If it is directly dripped on the slippers, even if it can prove that there are blood stains on the soles, it can no longer be tested for species and genetic markers, so filter paper test materials should be used for testing. Preliminary test." Zhou Zheng answered eloquently.

"Then why do you want to conduct a pre-test?" Cui Jun is not doing an assessment this time, but he is very puzzled. According to his usual work mode, if he suspects that there is blood on the sole of the slippers, he will put them directly into the evidence bag Just send it to the lab for testing.

"Because I suspect that there is no bloodstain on the sole of the shoe, I just want to prove my conjecture. In the bloodstain inspection step, we must first determine whether it is blood, then determine whether it is human blood, and finally determine the genetic marker. The test proved that there was no blood on the sole of the shoe, which saved meaningless work for the follow-up inspection department." Zhou Zheng expressed his thoughts.

"Okay, then go ahead, let me see if there is any problem..." Cui Jun's eyelids twitched. Others work to test items for blood stains, but Zhou Zheng wants to prove that the items are not stained with blood. This way of thinking is similar to that of normal people. There are some differences.

"Ok!"

Zhou Zheng immediately seized the time, his thinking was already running fast, so his movements had to keep up to prove his guess.

He took out the white porcelain reaction plate in the inspection box, put the filter paper that had just been rubbed against the sole of the slippers on it, then picked up the dropper in the bottle labeled "glacial acetic acid", and dripped it on the filter paper .

There was no delay in his movements, and then he dripped the benzidine absolute ethanol saturated solution on the filter paper.

After the whole process, the filter paper did not have any color change, it just became wet.

Zhou Zheng was not in a hurry, but waited silently. After about 2 minutes, he took out 3% hydrogen peroxide and dripped it on the filter paper.

Still no response!

"The soles of the slippers are not stained with blood." Zhou Zheng immediately concluded that the benzidine test had been completed, and he packed up the used things according to the prescribed steps.

"Zhou Zheng, can you explain the principle of the benzidine pre-test?" Cui Jun stared at Zhou Zheng and asked.

"The hemoglobin or heme in bloodstains has peroxidase activity, which can decompose hydrogen peroxide to release new ecological oxygen, and can oxidize colorless benzidine to benzidine blue, showing the positive color of emerald blue. Reaction." Zhou Zheng gave a very standard answer.

"You guys are really good!" Cui Jun nodded in praise. He had brought many interns, many of whom knew what happened and didn't know why. They memorized the reactions of various experiments, but they didn't know the principle.

That is not acceptable!

Because in addition to the benzidine test, there are also pre-tests such as phenolphthalein test, o-toluene test, luminol test, malachite green test, aminopyrine test, guaiac test, etc. Rote memorization is not enough. If you know the principle, you can use it flexibly.

Cui Jun was very satisfied with Zhou Zheng's smooth answer, and his eyes were filled with deep appreciation.

Li Yanyan has been staring at Zhou Zheng's operation. She has already mastered the benzidine experiment very proficiently, but if she suddenly asked her the principle, she knew that she couldn't explain it so clearly like Zhou Zheng did.

This is not a simple pre-test question, but the master asked too suddenly, this kind of assessment is no less than a random spot check.

In the knowledge of forensic medicine, there are many kinds of experiments. It is not so easy to master all these principles by heart and use them flexibly. It will take more time to accumulate slowly.

"Master, have the colleagues from the trace inspection department gone?" While Zhou Zheng was speaking, he had already sorted out the inspection box. The whole process was meticulous, and even the strict Cui Jun couldn't find any problems.

"We should be checking the stairs of the escape route now." Cui Jun thought for a while and said.

"I'll go find them." Zhou Zhengxin had a feeling, and quickly walked towards the entrance door.

"Are you still looking at the corpse?" Cui Jun asked hastily.

"Don't read it, the inspection is over, um, that..." Zhou Zheng stopped suddenly, grinned at Cui Jun, and said, "Master, I'm sorry, I forgot about the thing that is still in the assessment, my performance is okay ?”

"It's ok, you boy is much better than I imagined. It's okay, go to the scar inspector. Yanyan and I will take the body back to the center. I will wait for you until 8:7 in the morning at most. If you haven't come back, we will go Let's do the autopsy first." Cui Jun glanced at his watch, it was already 08:[-].

"Thank you, master!" Zhou Zheng was moved in his heart. He was not a fool, and he immediately heard the meaning of Cui Jun's words. It was an opportunity for him to participate in the autopsy. It's very rare, but now he must have something to confirm with the staff of the trace inspection department.

After Zhou Zheng walked out of the house, he saw a crying woman inside the yellow line. Her mobile phone kept ringing, and the hand holding the mobile phone was shaking. She was in a very bad condition.

The policeman next to her held a tissue in his hand and waited for her to take it away.

After seeing this scene, Zhou Zheng had a thought, and instead of rushing to the fire escape, he walked over.

"Ms. Wang, hello, can I ask you a few questions?" Zhou Zheng squatted in front of the woman, and there was no other possibility for anyone who could cry here, except for the deceased's mother, Wang Cuifang.

"Didn't you all ask me?" Wang Cuifang's voice was hoarse and she was still a little choked up as she spoke, obviously unable to accept the fact that her son was killed.

"In the next few days, we may ask you questions at any time. This is to catch the murderer of your son faster. I hope you can cooperate." Zhou Zheng's tone was very friendly and very patient. His minor Psychology majors are still very helpful in many cases.

"You ask, as long as you can catch the murderer, you can ask me as many times as you want, and I will tell you everything I know." Wang Cuifang wiped her tears and nose, looking haggard.

"You were the first person to find the body, tell me about the situation at that time!" Zhou Zheng said softly: "I know this is cruel to you, I guarantee that such a question will only be asked this time, I hope You can explain all the details clearly when your memory is clearest."

Zhou Zheng's eyes flickered with tenderness, trying to make Wang Cuifang feel as warm as possible, and not let her have too much psychological pressure.

Not long ago, Wang Cuifang witnessed the murder scene where her son was killed. This is a great blow to any mother.

Under such a mental shock, the memory will gradually become blurred. Zhou Zheng knows that it is cruel to ask these questions now, but if the time is too long, many details will be missed, and even the illusion of memory will be generated, which will breed non-existent things. Memory fragments, these will disrupt the detection.

"call……"

Wang Cuifang took a deep breath. A criminal police captain named Xia Yan had asked her before. She instinctively resisted, but the young man in front of her was very friendly. She also really hoped that the murderer who killed her son would be caught. Heng, said: "Then I will say it for the last time, let me think about it, and tell the whole process. Last night, I suddenly remembered that there were still a batch of purchase lists in the store that had not been settled, so I called Xiaoyong, but he I didn't answer it all the time, and I didn't think much about it at the time, but now it seems that he may have been killed at that time..."

　Thank you [Jiangnan Little Rich Woman] for your support!
　　
　
(End of this chapter)