Forensic identification of time of death has always been an extremely important topic in forensic research at home and abroad. Its research method has gradually developed from naked eye observation to advanced technical inspection such as histology, histochemistry, biochemistry and biophysics. However, due to the influence of various factors from itself and the objective outside world, it is impossible to have a completely unified standard, and the time inferred by various methods is only a rough time, which is not absolutely accurate. In addition, because any method is used alone for identification, there are great errors. Therefore, the determination of the time of death should be comprehensively analyzed by various methods. At present, there are mainly:

First of all, according to the hyperreaction.

After death, the tissues and organs of the body will respond to stimulation to a certain extent. There are many kinds of superlife reactions that can be used to estimate the time of death:

Muscle hyperreaction: within 2 hours after death, almost all muscles can contract after mechanical stimulation, especially biceps brachii, and it is not affected by environmental temperature. Two hours after death, most of them can only cause muscle contraction when they are hit. There was no obvious muscle contraction after death for more than 5 hours.

Subcutaneous hemorrhage after death: During the above-mentioned mechanical stimulation test, subcutaneous hemorrhage can be formed at the hit site. Its incidence rate decreases rapidly with the prolongation of postmortem interval. From: Long 'ai Free Resource Station

Pupillary hyperreaction: Dropping or injecting drugs into eyes within a certain period of time after death can cause pupillary reaction. 4 hours after death, dropping drugs such as ethephon or atropine into conjunctival sac can cause corresponding pupil contraction or mydriasis. If the drug is injected directly into the eye chamber, it can still be positive 20 hours after death.

Supernatural reaction of sweat glands: Under the action of drugs such as adrenaline and atropine, sweat glands can appear sweating reaction within 30 hours after death.

Second, the time of death is estimated from the changes of eyes and fundus.

IOP changes: Normal people's IOP is between 14 ~ 2 1 mmHg, and it can be reduced to 10 mmHg at10mmhg at 20 minutes after death. In the corpse with open craniocerebral injury, the intraocular pressure drops rapidly and the eyeball becomes soft.

Corneal changes: several hours after death, the cornea appears patchy opacity, 12 ~ 24 hours translucent, 36 ~ 48 hours highly turbid, and it is difficult to see through the pupil. When the eyes of a corpse are closed, the change of cornea is much slower. Corneal changes are also greatly affected by temperature and environmental conditions. The cornea of a corpse can remain transparent for a long time in the ice and snow.

You can also wet the cornea with a few drops of water or normal saline, and then observe the fundus changes with ophthalmoscope to infer the time of death, but this method is only suitable for one day after death.

Third, the time of death is speculated according to the phenomenon after death.

The face and limbs were cold, and lividity and rigor mortis began to appear. The time of death was 1 ~ 2 hours.

Lividity is distributed in fragments, and rigor mortis mostly appears, and the death time is 3 ~ 4 hours.

Necrophilia merged into a large area, the whole body appeared stiff, the cornea was slightly turbid, and the lips began to shrink. After dropping eye drops with mydriatic agent and mydriatic agent, the pupil still reacted and the death time was 5-6 hours.

Stiff rigor mortis is highly developed, the dead point can be completely subsided by finger pressing, the cornea is highly turbid, and the conjunctiva begins to autolyse. The time after death is about 12 hours.

Necrophilia can completely subside, parchment-like spots are formed, the cornea is highly turbid, scleral dark spots appear, and oral mucosa and conjunctiva autolyse. The time after death is about 24 hours.

The occurrence time of the above-mentioned postmortem phenomena is based on spring and autumn, which accelerates in summer and slows down in winter.

Corrupt abdominal distension begins at 8 ~ 10 hour after death in spring and autumn, 4 ~ 5 hours after death in summer and 48 ~ 72 hours after death in winter.

Corrupt green spots appear about 24 hours after death in spring and autumn, 12 hours after death in summer and 72 ~ 120 hours after death in winter.

Corrupt vascular network appeared 48 ~ 72 hours after death in spring and autumn, 65,438+0 ~ 2 days after death in summer and about 7 days after death in winter.

Hair is easy to fall off and appear rotten blisters, which appear 3 ~ 5 days after death in spring and autumn, 1 ~ 2 days after death in summer, and generally do not appear rotten blisters in winter.

The concept of corrupt giant began to appear 3 ~ 7 days after the death of Spring and Autumn, 2 ~ 3 days after the death of summer, and 15 ~ 30 days after the death of winter.

In midsummer, it takes about a month for the soft tissue of the corpse to liquefy and disappear, and the time will be shortened in the case of fly injury.

If the body is in the water, there are some postmortem phenomena for the presumed death.

The skin of hands and feet is soft and swollen, showing white shrinkage. If it appears on the palms and soles of the feet, the time of death is about 24 hours. If it appears on the back of hand and instep, the time of death is about 48 hours.

The phenomenon that the skin of hands and feet falls off like gloves, if it appears on a corpse in summer, its death time is about one week; Winter is about January; Spring and autumn days are about 2 weeks.

The concept of corrupt giant appeared in the spring and autumn of 7 ~ 10 days after death, 4 ~ 5 days in summer and1.5 ~ February in winter.

It needs to be emphasized again that the occurrence and development of postmortem phenomena are restricted by various conditions. When judging the specific time of death of the deceased, we should analyze and speculate according to specific problems, and we must never mechanically copy any data.

Fourth, according to the digestion degree of the stomach contents of the corpse, the time from eating to death is inferred.

Stomach food has its unique significance in forensic medicine. Forensic workers can not only infer the eating area, living habits and economic situation of the deceased according to the types and components of food in the stomach, but also provide clues for investigation and solving crimes; According to the degree of digestion and emptying of food in the stomach, we can infer the approximate time from the last time the deceased ate to his death, which provides a scientific basis for inferring the time of death and the range of activities of the deceased before his death.

Practice shows that the degree of digestion and emptying of food in the stomach depends on the nature of food. Take rice and vegetables for example. If the appearance of rice vegetables is complete, chyle is reduced, and only a small amount of food enters the duodenum, they should generally die within 1 ~ 2 hours after meals. If all the food in the stomach is chyle, only a few grains of rice and vegetable residues, the food has entered the large intestine and will die about 4 hours after meals. This article begins: If all the food in the stomach has been emptied, or only hard vegetable skins such as coarse skin fiber and kelp skin are left, you will die 4-6 hours after meals. If the contents of the stomach are meat or greasy and indigestible food, the time from eating to death should be extended accordingly.

The degree of digestion and emptying of stomach contents is used to infer the time from eating to death. Two factors should be fully considered: first, different people's digestive ability and the intestinal propulsion speed of food are different; Second, gastrointestinal peristalsis and digestive enzymes will continue for some time after death, so that food can continue to digest. This situation is more obvious when the body temperature drops slowly.

5. Estimate the time of death according to the urine volume in the bladder.

People who die at night can also estimate the time of death according to the filling degree of urine in the bladder. According to the habit of ordinary people, you should urinate before going to bed. If you see little urine in the bladder at autopsy, you may die within 2 ~ 3 hours after sleep. If you urinate heavily, you may die in the middle of the night. It's just that this situation is accidental, so it can only be used as a reference, not just to judge the time of death.

6. Inferring the time of death according to the life history of fly maggots.

The life history of fly maggots means that flies lay eggs and hatch into maggots, and maggots become pupae when they grow and mature, and then they break their shells and leave pupae on the spot to complete the generation process of fly maggots. Because the growth stage of fly maggots is regular, the life history of fly maggots can be used to judge the time of death, especially the time of death of late corpses.

The life time of fly maggots is restricted by many factors, among which season, temperature and humidity are the main factors that can be quantitatively analyzed. After long-term research, some forensic teachers of Southwest University of Political Science and Law and forensic workers of Chongqing Public Security Bureau have summarized a table of the relationship between the growth and development of fly maggots on corpses and the time of death for reference (see attached table). From: Dalian Free Resource Station

In addition, with the increase of the mature time of fly pupa, the color of its pupa shell changes from yellow-white, yellow, maroon and brown to dark brown, and from light to dark. Therefore, when inferring the time of death, we can also refer to the color of fly pupa and the broken pupa shell.

Inferring the time of death is one of the important contents of forensic medicine. However, it is very difficult to infer the time of death, especially for highly corrupt corpses or corpses with only bones left, because it is very complicated to determine the changes of corpses after death and the time range of inference is very large. In the practice of forensic examination, it is necessary to comprehensively analyze and consider various factors according to the specific situation of each corpse, and combine other evidence of the case to ensure the accuracy of the conclusion.

For reference only, welcome to adopt, hope to help you.