When a body is found, it is important for investigators to determine not only the cause of death, but also the time. To do this, a forensic expert goes to the scene of the incident and can determine the age of death. What methods are used for this, how insects help in this matter, and how accurately the moment of death can be determined, “Gazeta.Ru” on the Day of Criminal Investigation Workers in Russia was told by a forensic expert, pathologist, candidate of medical sciences, senior researcher of the pathology group terminal conditions Research Institute of Human Morphology named after. acad. A.P. Avtsyn Russian Scientific Center for Chemistry named after. acad. B.V. Petrovsky Boris Kulbitsky.
– Until now, determining the time of death of a person remains difficult for forensic experts. Why?
– Indeed, we have studied many biophysical and biochemical processes occurring in the human body, including during death and the period after it. But despite the development of modern technology, determining the time of death still remains a complex process.
A forensic expert involved in determining the time of death must take into account the individual characteristics of the body. Age, health status, physical fitness, weight, height, presence of any diseases and medication use can affect the rate of post-mortem changes. In addition, external conditions are taken into account, such as temperature, humidity and oxygen availability in the air, and the influence of insects. Of course, when a person dies, there are several stages of changes in the body that can help us determine the time of death. But the more time passes from the moment of death, the more the accuracy of establishing its time decreases.
– What methods do forensic experts use at the scene of discovery of a body to determine the age of death?
– In forensic medicine, a combination of methods is used for this. One such method is to measure the cooling rate of the body. Before measuring body temperature, note the temperature of the air or water where the corpse was located. Then the body temperature is measured in the rectum, after an hour the procedure is repeated and the indicators are correlated.
At an ambient temperature of +20°C, the body of an adult usually cools down by 1°C in one hour. Moreover, in the first hours it is a little faster, and after six hours the drop in body temperature slows down, and it will decrease by 1°C in 1.5-2 hours. In arid (dry) and arctic climates, processes proceed differently and the thermometry value drops.
Another important sign is cadaveric spots – these are areas of skin with a bluish-violet color. They are formed due to the cessation of blood circulation, then it falls under the influence of gravity to lower areas of the body. In these places, hemolysis occurs (the process of destruction of red blood cells and the release of hemoglobin) of the blood, which leads to the formation of cadaveric spots. They begin to appear 1-3 hours after death and become fixed after 6-12 hours.
– What do you mean become fixed?
– Before that, they can “move.” For example, if the position of the body after death and the formation of cadaveric spots has changed, then we can notice where the primary spots were located by the color of the skin. Secondary spots are usually paler and have a different localization. Their detection is important for ascertaining the post-mortem movement of the body.
When you press on the cadaveric spot, it disappears and restores its original color within 10 seconds to 3 minutes. This occurs between 1 hour and 4-6 hours after death. 7-12 hours after death, color restoration occurs within 3-5 minutes, and if 13 to 24 hours have passed, then it can last from 10 to 15 minutes.
The latest period when cadaveric spots still fade and restore their intensity is 24-48 hours. Starting from the second or third day, when pressed, they no longer change their intensity.
– Can you also determine the time of death by the state of your muscles?
– Yes, the third sign by which we can determine the time of death is rigor mortis. This is a complex process, but to simplify it, it can be described as follows: due to the cessation of blood supply, biochemical changes begin in the muscles, which cause rigor. This process begins to appear after 2-3 hours and reaches its peak after 12-24 hours, but disappears after 36-48 hours.
But in cases where more than three days have passed since death, and during this time the body was in conditions conducive to decomposition, the process of decay begins. This sign also helps determine the time of death. Typically, the process of decay begins to actively develop within the first 24 hours after death. In the period from 24 to 48 hours, cadaveric greenery appears in the armpits and abdominal area, and on the second or third day it covers most of the body. From the fourth day to a week, the skin becomes dirty green, the venous network is clearly visible on it, and the body becomes flabby.
– Can external factors speed up this process?
– Of course, high temperature, high humidity, infectious diseases, that is, the presence of bacterial flora in the body, accelerate this process. But in hot and dry climates, where moisture evaporates faster, the process of mummification can develop.
If the human body was in a humid environment, in the absence or lack of air, including in flowing water, then the so-called fat wax can be fixed. This is a kind of fatty substance that covers corpses. In such conditions, rotting does not occur, and the corpses are preserved, as it were, covered with a fatty film.
Fat wax can also cover internal organs, muscles and the brain. This process can be described as saponification, which occurs through anaerobic bacterial hydrolysis.
And the forensic expert records all this in order to most accurately establish the duration of death, because he participates in investigative actions and must collect the maximum evidence base. A specialist will never rely on one factor; an integrated approach is needed here. This is important because the accused may have an alibi at the time the crime was committed, and the accuracy of determining the time of death of the victim depends on whether the truly guilty person will be brought to justice.
– What other methods of determining the time of death can a forensic expert apply at the scene of discovery of a corpse?
– This, for example, is the “cat pupil”, that is, the narrowing of the human pupil after death when the eyeball is slightly compressed by a forensic expert. It is strongly pronounced the first time after death, but after 12-13 hours it will no longer be noticeable. The reaction of the iris to chemical irritation is also used. A special solution is dropped into the eye and the pupil is observed to constrict and dilate over a certain period of time. This allows you to evaluate the reaction of muscles to stimuli.
We also look at the formation of idiomuscular tumor, which forms when a muscle is struck. Forensic experts have a special iron rod with which they deliver measured blows, usually to the biceps brachii muscle.
In the first four hours after death, the swelling from the blow is well expressed; if 7 to 12 hours have passed since death, then a dent forms at the site of the blow, and after 12 hours there is simply no reaction.
– Do you study the environment? Does the location where the person was found provide any clue as to the time of death?
– When a corpse is discovered, special attention should be paid to the environment. Examination of insects found on or near the body can help determine how long ago the death occurred. The larvae that grew on the corpse, as well as the plants underneath it, may be in varying stages of flowering or development.
In the metropolis, the main insects are flies. Their appearance on a corpse can be tracked by clutches of eggs, which usually appear within 4-6 hours. The larvae appear after about 12-24 hours, then the pupae appear. Sometimes several generations of flies appear on the body, which also gives the forensic expert clues. But, unfortunately, it is impossible to determine the time of death based on the species of insects that are on the body. However, this sign can be used to determine whether an event occurred in the area where the body was found.
– Now you have collected all the data that may be useful to you to determine the time of death. What happens next?
– After work at the scene of the incident, the corpse is transported to the forensic morgue for a sectional examination, which is carried out by thanatologists.
It also describes all of the above phenomena. Afterwards an autopsy is performed, the condition of the organs is described and their pieces are removed for forensic histological examination. After all, the insides are also subject to autolysis, especially the pancreas, liver and other organs containing digestive enzymes. And depending on which organs and how susceptible they are to decomposition, the doctor draws conclusions about the time of death.
Biochemical tests may also be prescribed. The thanatologist takes samples and passes them on to forensic biochemists. The process involves far more than just one forensic expert going to the place where the corpse was found, as many people think.
– What kind of research can be ordered?
– After an autopsy, it is possible to determine the duration of death by the content of certain substances in tissues and organs. For example, in the vitreous body of the eye after death, the concentration of potassium (in this case it is a product of tissue breakdown) gradually increases. Testing potassium levels can provide insight into the time that has passed since death.
There is another specialty in forensic medicine – forensic genetics. She studies DNA and RNA. DNA and RNA degrade at different rates, for example, RNA degrades faster than DNA, so analyzing the degree of degradation provides fairly good information for judging the age of death. However, this process takes different amounts of time in different tissues. However, this study is not always prescribed.
– Are there devices or special devices for determining the time of death?
“Many age-of-death devices have been created, and if one of the development teams achieved maximum accuracy, this device would probably become famous throughout the world.
The fact is that all these devices did not provide significant advantages in the speed and accuracy of determining the time of death. In addition, some of them measure body and environmental temperature, including through a liver puncture. But it was precisely because of the puncture that the method was not widely used. The medical examiner who is at the scene of a death may make a puncture, and the next examiner who performs the autopsy, even if noted, may misinterpret it. This affects the results.
But microfluidic test strips have been created that have proven themselves and are widely used. They require no damage and analyze biomarkers in body fluids, such as potassium. They react chemically with the liquid, resulting in a change in color or indicator.
– They are also trying to teach AI to determine the time of death of a person. How do you assess these prospects?
– I won’t talk about specific departments, but I know that this area is actively and successfully developing in Moscow medical institutes.
Artificial intelligence has proven itself well, but much depends on the developer. It is very important that this person works closely with forensic experts. This is necessary to properly evaluate the big data on which the AI will learn.
Unfortunately, some IT specialists do not always listen to doctors, but forensic science, especially thanatology (the study of death), is a very delicate field. There are many controversial issues that need to be taken into account. If this big data analysis can properly process information through self-learning, then we will have a big breakthrough in this area of AI application.
