C12 Strangulation or suffocation(1)

"Assuming that the victim's body is located in a higher sulphur content soil or in a gaseous environment, it is not possible to obtain more sulphur from the surrounding environment because the victim has ceased his or her activities, which would not indirectly increase the sulphur content of the insects. However, for insects that live in this sulphurous soil environment and have a suitable temperature to provide, it may be possible to provide some geographic information, not to mention a certain amount of sulfur in the air. This is the basis for my conception of the location of the victim's body based on insect information, which helps me to understand what the real situation is. Second, what I need to know is whether it would be useful to infer the time of death in the wild from the length of the insect body, taking into account the fact that the body length of the insect during its development is strongly influenced by temperature. This requires us to go to the site and build an experimental model. "

"There are many kinds of insects. Are you sure you want to test them?"

"There is a certain regularity in the appearance of each type of carnivorous insect in the body. The first flies in the body were mainly bipteridae, especially the giant tail alligator, silky green fly and giant head golden fly, which were the three most typical species. Among these three species, the giant tailed alligator flies are the most common insects in China, except in Xinjiang and the cold regions. The population of the eastern region and the area where the rainfall is over 500 mm is large, which is often dominant in the corpses of early spring and late autumn. Although the rainfall in Hunan Province was more concentrated from May to July, the average annual rainfall ranged from 1350 mm to 1450 mm. Therefore, the climate and environment conditions suitable for the growth of the giant tailed Arias in the early spring season in southern Hunan Province. I have identified the maggots found on Su Heshan's body and confirmed them to be giant tail alligators. "Therefore, I decided to use the giant tailed alligator as an experimental target, using it as an opening to find out the truth about the murder of Su Heshan."

"Your idea is not bad. However, if you wish for me to provide you with something for you to investigate, I can accept it. However, one thing to clarify is that I can only help you investigate in secret, and the scope of authority for the investigation is very limited."

"Alright, what's your second condition?"

"We found a young woman strangled in a building in Sha Lu, south of Changsha City. The prints and footprints were wiped clean. The killer had wrapped the nylon rope in a paper bag and killed the victim. There were no fingerprints on the paper bag. It was evident that the murderer was either not very professional or had done his homework before the murder. The available evidence does not establish the identity of the suspect. There is an important person from the Ministry of Public Security who is coming to the Public Security Bureau to inspect the case next month. We want to finish the case as soon as possible before he arrives. So, you have to do us a favor. "

"What are you doing, just say it."

"Aren't you working on forensic entomology?" Ding Wei looked at Shen Yuan who had an expression of anticipation and said, "Coincidentally, there are also some insects on the body of the victim in this case, so we can consider whether we can use the insects to find some clues, such as the time of the murderer or any other useful information, and most importantly, whether we can calculate the time of the body's death accurately."

"What if the insect information I provide is of no help to your case?"

"Let's just take it as if you've actually trained for a bit. Let me show you how big of a difference there is between the actual situation and the experimental results."

"Well, I was going to do some indoor insect experiments at school for a few days, and I wouldn't be able to do field experiments in Jizhou until April. I'll give it a try during this period of time. "

"Then we have a deal."

The Provincial Public Security Forensic Testing Center, which covers an area of 1,000 square meters, was built and put into use in May of last year. There are five autopsy rooms and seven autopsy tables for more than 40 forensic doctors to use in every sub-bureau of the province. If a murder occurs, the forensic doctors will be busy here.

After walking through the door, he saw that the interior was divided into a work area and an office area. The work area was only used for the transportation of corpses. The office area was where the usual forensic doctors worked. The most he did was to kill the rats by various means, then put them in the field or in the room or at different places or at different temperatures to observe the gathering of insects, lay eggs and adults, have never personally come into contact with a human body, let alone collect insects from a human body to get an understanding of the case. Occasionally, he would follow the forensic doctor from the Forensics Center to the field to observe insects on the body, but he had never calculated the actual time of death. Ever since he was young, he had loved reading all kinds of crimes and was very curious about the cause of the crime. But since he had agreed to Ding Wei's request, he couldn't help but be worried that he would make a joke out of himself or embarrass Ding Wei. Now, he could only brace himself and follow Ding Wei here.

Walking up the stairs and passing through the corpse passage, Shen Yuan's heart slightly tensed up. However, after entering the office, his mood immediately became tranquil. There was plenty of light in the office, and there was no smell of formalin or blood. From the monitoring of the office, the autopsy room could be seen in real time. As long as the autopsy room is in use, the room's monitors will record the entire process of forensic anatomy, according to an automated video of moving images, Mr. Liu said.

After passing by a draught chamber, there were two dissecting rooms. The dissecting table was divided into two layers, the upper layer having many small round holes. Human tissue dropped during the autopsy can be dropped through a small hole into the lower layer so as not to interfere with forensic work. The transparent plastic pipe attached to the tap can be used to flush water to clean the body, or it can be drawn under negative pressure to suck away the sewage from the dissecting table. There was also a crusher under the table, which could crush the dissecting debris to prevent blockage in the sewers. The dissected waste water is removed by purification and will not pollute the nearby environment.

Other than Public Security Police Ding Wei, there were two other people accompanying Shen Yuan.

"This is the provincial police medical examiner Liu Zhiwei. He will be in charge of the autopsy." Ding Wei pointed at the short and sturdy middle-aged man.

"This is a reporter from a legal website called Luo Yudao, who is the author of 'China's Legal Status and Worries'. He recently wanted to write a book on law and crime, was interested in this case, and intends to follow us through the process. " Ding Wei pointed to a tall and handsome young man and introduced him.

Luo Yin and Ding Wei were law students at Renmin University of China. The difference between Luo Yin and Ding Wei was that he stayed in the university to study for graduate students, while he directly went to the provincial public security police to work as a criminal investigator after graduating from university. Since the publication of the book "The Current Situation and Worries of China's Law", Luo Bei has gained a bit of fame in the judiciary. In contrast, he was obscure.

Shen Yuan and Luo Yin first looked at the scene photos and the crime scene records. Two hairs collected at the scene were subsequently tested for mitochondrial DNA, which was consistent with the DNA sequence of the deceased.

A dead woman was removed from the freezer and placed on the dissecting table.

The body was in the swelling phase. On the eyes of the deceased, there were obvious spots of bleeding inside the lower lid: signs of neck compression. Bleeding spots form when capillaries in the tissue are pressurized. The human blood circulation consists of arteries, veins and capillaries. The arteries press the blood carrying oxygen out of the heart and into the capillaries. At the capillaries, the blood gives off oxygen to the tissues and returns to the veins, where it is sent to the heart. If pressure is applied to the neck, the blood in the veins will flow backwards into the tissues, causing the fragile capillaries to rupture. It takes 300 to 350 newtons to destroy the arteries, and 25 to 30 newtons to destroy the veins. There is no doubt that the bleeding spots in the deceased were caused by pressure of venous return.

The postmortem records showed blood from capillaries in the eyelid. Shen said it was a blood spot where the capillaries had ruptured, not the blood that Liu had thought they were.

"This is a very simple question. Vascular filling occurs after death, while subcutaneous hemorrhage is when blood escapes from the bloodstream. This is easy to identify because only living people have subcutaneous bleeding. The victim should have been strangled within a very short period of time, which is why the blood vessels we see are so bloody. " Liu Zhi Wei's tone revealed some disdain towards Shen Yuan's words.