How long are fingerprints stored on various items? How long does it take for experts to identify a criminal using fingerprints? How long do fingerprints last?

Many people are interested in exactly how long fingerprints are stored on a particular item. This, as a rule, does not mean that a person is planning to commit a crime - this question is often asked by professional criminologists or ordinary fans of detective novels. Read more about this below.

How do fingerprints appear?

Human skin, like that of all mammals, consists of 2 layers:

• upper – dermis;
• lower – epidermis.

Due to uneven fit, interpenetration and different joint densities, characteristic folds are formed. They are called papillary patterns. Specifically, they help a person hold smooth objects with his fingers, creating increased friction - the mechanism of action of car tire treads is built on the same principle. The described structure also serves as protection against calluses - if the layers of skin did not have many points of contact, blisters would form literally at the slightest impact.

While in almost all mammals the folds are arranged chaotically, in humans and monkeys they form unique patterns consisting of parallel lines.

This feature was initially noticed in Ancient China. Even before our era, it was actively used to identify people.

How long is a fingerprint stored?

In forensic science, a fingerprint is called a fat mark. This name is no coincidence, because the basis of the print is made up of substances produced by the sebaceous glands. The latter are found in large quantities on the pads of the fingers, while, for example, they are practically absent on the palms themselves. Fat is secreted constantly and around the clock, accordingly, a trace of it remains on literally all objects that a person touches, even fleetingly.

After a certain period, an imprint on any surface begins to disintegrate in the following sequence:

• moisture evaporates first;
• then solid particles fall off.

For example, on glass at temperatures up to +28 ° C, and under the influence sunlight The print is completely decomposed within 2 hours. It is less quickly destroyed by rainwater.

On average, the process of print decay lasts from 2 to 5 days. Speed ​​is significantly affected by:

• air temperature;
• humidity;
• presence of wind, etc.

To a lesser extent, the shelf life of hand marks depends on the composition of the sweat-fat substance of a particular person and the intensity of its production. It is known that approximately 10 percent of people on the planet completely lack:

• amino acids;
• proteins.

Their prints are not visible with standard substances (allocean and ninhydrin).

In general, for most people, skin secretions have a very noticeable stickiness, which allows special powders to adhere well to their traces. However, each person, as previously mentioned, has a unique intensity of activity of the sweat and sebaceous glands. Some people have wet hands all the time, while others suffer from excessive dryness of the dermis. A number of the following factors also stimulate production:

• physical exercise;
• excitement;
• heat.

Excessive amounts of sweat and fat on the palms create a blurry impression, in some cases completely unidentifiable. At the same time, its lack leads to fragmentation of the print - the papillary pattern turns out to be extremely thin and often dotted. Finding it can be very difficult.

The duration of preservation of fingerprint traces is also influenced by the properties of the object itself. For 3-7 days will be lost imprint left on:

• writing paper;
• newspaper;
• cardboard;
• unpainted wood.

Prints on hard and smooth surfaces will last for several months (and sometimes years):

• glass;
• metal;
• porcelain;
• polished furniture.

It is almost impossible to detect traces on:

• textiles;
• rough surfaces;
• suede.

Often, prints are found that have been preserved in a closed room with a consistently low temperature after 5 or more years. At the same time, we must not forget that forensic science does not stand still. Even fuzzy traces (as well as old and fragmented ones) can be recognized and removed using modern equipment.

However, the classical method, based on the action of iodine vapor, helps to detect handprints left from a week to 3 months ago.

Laser-luminescent technology can easily detect traces within 30 days.

In particularly difficult situations, they also resort to vacuum vapor deposition of certain metals - this technology is quite expensive and therefore is not used in ordinary cases. Using this method, it is possible to detect fingerprints even after 2-3 years.

How to take fingerprints

For those who want to try themselves as a forensic scientist, it will not be difficult to make their own fingerprint powder. The simplest method:

• take the piece of glass;
• hold it over a burning candle;
• scrape off any soot that has formed.

(Nazarenko A. A.)

(“Forensic expert”, 2008, N 2)

INFLUENCE OF ENVIRONMENTAL CONDITIONS ON THE PRESERVATION OF FAT TRACES OF HANDS

A. A. NAZARENKO

Nazarenko A. A., applicant for the Department of Criminalistics and Legal Informatics, Kuban State University.

Immediately after the completion of the trace formation process, sweat and fat traces, like any other traces, undergo various influences and begin to change. Two ways of changing the sweat and fat traces formed on an object should be taken into account.

One when latent traces are in normal conditions(indoors, at a temperature of 20 degrees C, air pressure of 760 mm Hg, normal air humidity), can be defined as natural aging. This is primarily the loss of moisture by the sweat-fat substance as a result of surface evaporation, diffusion into the depths of the receiving object, absorption by dust and other contaminants. Evaporation occurs mainly in sweat, since it contains a high moisture content.

Another way of changing the sweat-fat trace is associated with the active influence of the environment, expressed either in slowing down the processes of natural aging, or in activating these processes. It seems useful to dwell on the conditions of both.

A. Effect of moisture.

The most common cases of the influence of excess moisture are increased air humidity, exposure to rain, in ponds, and dew settling. If the fingerprints have not yet lost moisture, then due to the wetting of the sweat component with water (contact angle = 0 degrees C), the traces will spread, which will be greater, the more representative the sweat component is. Even if the sweat traces have dried, due to the water solubility of the compounds that make up the sweat component, they will be washed out. Pure sweat marks on the glass are completely destroyed after a two-hour exposure to the sun (at a temperature of +28 degrees C) and then a 10-minute exposure to heavy rain.

The more fat there is in the sweat-fat substance, the better the latent traces are preserved in water. Therefore, traces of sweat and fat on objects that have been in water can sometimes persist for significant periods of time. But processing such traces with a developer must begin immediately after drying the object.

Low air humidity causes increased evaporation of trace moisture, or rather sweat moisture.

B. Temperature effects.

An increase in temperature contributes to the intensification of the aging process due to increased evaporation of moisture from sweat and oxidation of the fatty components of the sweat-fat substance. Moreover, how the temperature rises also matters. A slow and prolonged increase (for example, exposure to solar heat) causes the spreading of the sweat-fat substance over the receptive (especially hard and smooth) surface and the “spreading” of the skin pattern.

The temperature limit, after which the spreading of sweat fat traces is observed, is determined by the melting temperature of the fat component (according to K. A. Kalantaevskaya, the melting temperature of sebum is about +30 degrees C). A sharp and significant increase in temperature (for example, during a fire) causes charring of the organic compounds of the sweat-fat substance of the trace, which leads to its greater stability.

Lowering the temperature contributes to the long-term preservation of sweat marks, as it slows down the aging process. O. Rispling claims that “fingerprints on objects frozen in ice could last forever - like mammoths in Siberia.”

B. Dustiness of the environment.

Increased dust content contributes to earlier destruction of traces due to the adhesion of dust particles to the trace-forming substance - in a sense, the “manifestation” of traces by dust.

The spread of dust is facilitated by atmospheric factors such as wind. In addition, the wind increases the evaporation of moisture from the tracks.

Directions for using information about conditions environment.

First, this information helps create optimal conditions storage of seized objects with traces of sweat. We can recommend:

— use packaging insulating from the environment, in particular polyethylene, to protect seized objects from undesirable environmental influences and equalize storage conditions;

— moistened objects with supposed latent traces should be delivered to the fingerprint laboratory in a vessel with high humidity;

- avoid heating the seized objects - do not place them near heat sources;

— store trace-receiving objects at low temperatures.

Secondly, they are used to select the optimal method for identifying invisible traces. Recommendations may also be offered here:

— in the case of moistening trace carriers, the detection method should be based on the use of developers that interact with the fatty component of the sweat-fat substance (as a more stable one); the use of developers based on interaction with water-soluble compounds included in the sweat component (sodium chloride, proteins and amino acids) should be excluded;

— It is not advisable to use powder developers for objects covered with dust.

Thirdly, this information is necessary to explain the reasons for the non-detection of sweat and fat traces under certain environmental conditions.

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At work; with hand marks great importance have periods of preservation of such traces on various surfaces under various conditions. Knowing these terms allows you to correctly select the appropriate means and methods for their detection, and determine the relevance of the detected traces to the crime event. On the other hand, an urgent problem in the investigation of many crimes is establishing the time of formation of handprints on objects at the scene of the incident.

Ignorance in this regard often leads to the fact that the search for handprints in crimes two or three weeks ago is not carried out due to the incorrect assumption that it is impossible to identify such “old” traces. In other cases - on-

turnover: objects on which traces remain for only a few hours are sent for research several days and sometimes weeks after their discovery.

The importance of the temporal characteristics of handprints for crime investigation can be illustrated by the following examples.

When examining the scene of the murder of Ms. T. (in her apartment), on the oil-painted wall next to the corpse, experts found clear traces of hands, which were diagnosed as quite fresh. Soon the suspect L. was identified and a fingerprint examination was carried out - with a positive result. However, during interrogations, L. categorically denied his involvement in the crime and claimed that he could have left the traces eight months ago, when he came to repair the phone. Obviously, in such a situation, determining the age of the discovered traces was crucial to confirm the testimony of the suspect or incriminate him in the murder.

In another case, as a result of an inspection of the scene of the murder of the B. spouses, a large number of handprints were seized. Comparison with the fingerprints of the victims made it possible to exclude most of them - except for the traces on plastic bags: checking the handprints of all relatives, neighbors, and acquaintances using these traces did not give any results, and thus it could be reasonably assumed that they belonged to the criminal. However, the absence of traces on other objects that the criminal held in his hands gave rise to a special study, the purpose of which was to determine the time of formation of traces on plastic bags. The data obtained indicated that the shelf life of these traces exceeded five months. This means that they could well have been left by unauthorized persons (for example, sellers). This allowed a different assessment of the seized traces and their significance for the evidentiary process.

The shelf life of handprints depends primarily on the properties of the sweat-fat substance, determined by its composition and quantity. Some people (about 10%) have no proteins or amino acids in their sweat secretions. Because of this, it is not possible to reveal traces of their hands with ninhydrin and allokean. All people's sweat secretions have sufficient stickiness to ensure that the powder particles are firmly attached. However, different people An unequal amount of sweat is released, and it depends on a number of circumstances. Excitement and physical stress cause increased sweating; In conditions of low air temperature, sweat production decreases, and in hot weather it increases. Excess sweat on the hands leads to blurry, indistinct, and sometimes even negative appearance of the capillary lines. A lack of sweat fat causes incomplete display of papillary lines; they turn out dotted and unusually thin. Such marks are not able to retain a sufficient amount of powder and therefore are poorly colored.

The composition of the sweat-fat substance in traces and its amount

They undergo changes over time. Under the influence of temperature, air humidity, its movement, dust in the trail, the amount of moisture, salts decreases, amino acids decompose, etc. The adhesive properties of the trail substance decrease over time, it loses the ability to retain powder particles and adsorb iodine vapor. Amino acids last the longest, but over time they also stop reacting with ninhydrin - the trace disappears, it can no longer be developed and used as evidence.

It has been established that the shelf life of traces also depends on the properties of the object on which they are found. If the mark is on an object whose substance absorbs moisture (paper, unpainted wood), then the ability of such a mark to react with powders will disappear much sooner than that of a mark located on a surface that does not absorb or poorly absorbs moisture (glass, porcelain, etc.)

In table 11 shows experimental data on the retention period of sweat fat traces and the possibility of their detection by various methods. It indicates maximum terms of preservation of traces. The main part of them is preserved for no more than half of these periods.

In table 12 contains the maximum limitation periods for traces that can be detected by the most common and effective fingerprint powders.

It should be borne in mind that the information provided about the shelf life of traces and the time of their reaction to certain reagents is indicative in nature.

The data presented give an idea of ​​the conditions under which the methods used are most effective, and therefore they are recommended to be taken into account when choosing methods for identifying handprints, depending on their age, the properties of the receiving surface and the properties of the reagents themselves.

Establishing the time of formation of the identified traces on the furnishings of the scene of the incident is an urgent, but rather complex problem. In the simplest version, this can be done using those given in the table. 10 and 11 data. For example, if in the summer traces are detected with powder on a painted tree located in the open air, then it can be assumed with a high probability that they are no more than 11 days old.

However, tabular data must be used quite carefully, within certain limits and mainly in a probabilistic manner.

Form. Too many factors - some of which are simply impossible to take into account - influence the retention time of traces.

Table 12 Maximum periods of limitation of traces, detected by powders

Powders used

Carbonyl iron, malachite, aluminum, zinc oxide

“Malachite”, carbonyl iron, “Ruby”, graphite, copper oxide with soot, wax

“Malachite”, carbonyl iron, copper oxide, manganese peroxide, talc, lycopodium

“Malachite”, “Ruby”, copper oxide, lead oxide

“Opal”, “Topaz”, “Malachite”, zinc oxide Aluminum

“Topaz”, copper oxide with soot, carbonyl iron

Chalk, manganese peroxide, lead carbonate

Copper oxide with soot, “Malachite”, “Opal”, zinc oxide

“Ruby”, “Topaz”, “Opal” (only for non-ferrous metals), copper oxide with soot, zinc oxide

“Topaz”, “Opal”, zinc oxide, “Malachite”, carbonyl iron, zinc oxide, lead oxide

“Topaz”, carbonyl iron, “Malachite”, zinc oxide

On varnished surfaces painted with nitro and synthetic enamels - “Opal”, “Malachite”, copper oxide with soot, zinc oxide, aluminum On surfaces painted with oil paints - the same powders

Graphite, copper oxide with soot, infrared photography, fluorescent powders, ultraviolet photography

Fabric, wax, lead oxide

Of those methods and means that are usually used at the scene of an incident to identify handprints, iodine powders and vapors have certain temporary signs that allow us to judge the age of the traces. For powders, they consist in a change in the adhesive properties of the sweat-fat substance over time, as the traces dry out. Experienced experts usually use this property, distinguishing old traces from fresh ones by the degree of adhesion of powder particles to the sweat-fat substance. Fresh traces of lapillary lines are intensely colored even when lightly touched with a magnetic or nap brush with a small amount of powder, and to identify old traces, the powder must be rubbed into the surface with a certain force.

For iodine vapor, a temporary sign is a decrease in the contrast and clarity of the detected traces as a result of the “spreading” of the resulting layer and a decrease in the ability of organic substances to react with the developing substance.

The presence of such fairly easily established dependencies makes it possible to roughly date the traces when conducting special studies. Moreover, iodine vapors have more clearly defined signs, and if during an inspection of the crime scene there is a need to determine the age of sweat marks, then it is better to use iodine vapors to identify them.

An indispensable condition that ensures the possibility of further research of detected handprints to establish temporal characteristics is their removal from the scene of the incident along with the tracer object. The method of copying traces onto sticky layers significantly worsens and sometimes eliminates the possibility of determining their age. During the inspection in such cases, it is also necessary to include in the protocol the recording of environmental factors that affect the retention time of traces: moisture, high or low temperature, exposure to open air, dust, etc.

In practice, to establish the time of formation of traces, a simple method can be used, with the help of which, in the above example, it was possible to establish that traces on plastic bags could have been left at least five months before their discovery. For this purpose, the clean side of the bag, “on which there were handprints, was drawn into squares and experimental fingerprints of several people were left. Then, periodically, once a month, several squares were treated with the same powder that was used to reveal handprints at the scene of the incident. Through a comparative study of the color intensity of detected experimental and

of the existing handprints, it was possible to date them and thus put forward an informed assumption that the traces could well have been left not by the criminal, but by a random person.

Similar results could have been obtained in the second case. To do this, the wall on which handprints were found would have to be drawn, a series of experimental traces with different trace formation conditions should have been left on it, and they would have been examined in a similar way. Perhaps this would have required continuing work in within the entire eight months indicated by the suspect, but most likely the experiments could have been completed in a shorter period.1

The disadvantage of this method of dating traces is that it does not take into account the influence of the amount of trace substance on the period of its preservation: the more substance, the better, other things being equal, the traces are preserved and the later they can be identified. Thus, the last of fresh fingerprints imprinted in a row are revealed by powders worse than older traces with a large amount of trace substance. When establishing the time of formation of hand marks, this circumstance must be taken into account, and when setting up experiments, various conditions for the formation of hand marks must be provided.

In addition to powder methods and the use of iodine vapor for dating hand marks, in some cases the silver nitrate method can be used, which, along with identifying traces, makes it possible to record the time-dependent effect of the spatial movement of chlorine ions. Thus, in a dry, heated room, the trace of the patchwork pattern becomes unclear within a month, but the image of this trace on the back of the paper remains suitable for identification for three months. Identifying traces that are five or six months old rarely gives a clear picture. Temporary signs are also characteristic of the ninhydrin method: as the period of limitation increases, the brightness of the detected handprints also increases.

The laser method and TVN have great potential in terms of establishing time dependencies. Thus, the TVN method allows you to accurately differentiate between fresh and old marks, regardless of the number of touches preceding the formation of marks. When a laser detects long-standing traces, the effect of luminescence shifting from yellow-green to orange is observed

1 Such studies must be carried out as an examination. The maximum purity of the experiments can be achieved if experimental handprints are obtained from a suspect.

zone of the spectrum of groups of lines associated with some components of the sweat-fat substance. This makes the laser method quite promising for determining the time of formation of hand marks /;

A correspondent of the Minsk-Novosti agency found out how fingerprint examinations are carried out.

Let’s imagine a situation: a trio is drinking in a rented apartment, a quarrel breaks out, one of the participants grabs a knife, in a fit of anger kills his drinking buddies and hastily retreats. In the morning, the owners come to get the keys and see two bloody corpses in the kitchen. Of course, they immediately dial 102. Soon police officers, investigators, experts are already working there...

Law enforcement officers are paying attention to traces of a recent feast. There are two corpses, and three glasses from which the “little white” was consumed. Let's say that in a hurry or when he was drunk, the killer did not take care to remove the evidence.

The expert identifies fingerprints on the glasses and, through electronic communication channels, transfers them to colleagues at the office of the State Committee for Forensic Expertise (SCFE) of the Republic of Belarus in Minsk. Those, in turn, identify them in automated fingerprinting information system(ADIS).

I decided to conduct an experiment. Knowing for sure that my fingerprints are in the database - many years ago I underwent mandatory fingerprint registration - I left a mark on one of the three mugs, inviting Olga Porechnaya, the state forensic expert of the Department of Forensic Expertise and Accounting of the State Committee for Social Security of the Republic of Belarus in Minsk, to establish who he belongs. The girl applied fingerprint magnetic powder to the surface of the cups with a special brush.

Then, using tape, I transferred the developed trace onto a paper backing, took a photo and sent it to my colleagues in the department, who, by the way, work around the clock.

They assigned a code to the image and manually drew the most obvious signs of the trace in a special program to speed up and simplify the process. Next, it’s up to the technique: identification with the dacto cards available in AFIS.

Among millions of fingerprints, within 15 minutes, the program determined a list of persons most suitable for the location of identifying features - that is, those who could presumably leave it. Then the expert once again personally compared the traces seized from the crime scene with the suspects’ data cards. And - voila! - the most suitable one turned out to be mine. The whole thing took no more than 40 minutes.

In order to prove the involvement of a person in the commission of a crime, the fingerprint must match the trace in more than one way - more than a dozen are required.

If this does not happen, the expert will never give a positive conclusion - the possibility of undeserved punishment cannot be allowed. This kind of examination should give an unambiguous answer - without any “maybe” or “most likely”.

There are three types of patterns: arc, loop and curl. However, there are no identical fingerprints. Even in identical twins, at first glance they can be very similar - the same type of pattern, shape, size, but the papillary lines are still located differently.

The Daktocard of the alleged criminal may not be in the database at all, but the trace will coincide with what was previously identified at the scene of another crime. Experts will definitely pass on such information to the concerned authorities. .

- Of course, when committing a burglary, an expert will not cover the entire apartment with powder, recording all traces in a row, - explains the specifics of the head of the forensic accounting department of the department of forensic examinations and accounting of the State Committee for Social Security in Minsk, Maxim Duk. - Together with the investigator, they will model the possible trajectory of the criminal’s movement, paying special attention to those places where something is missing or is out of place.

Not all surfaces are treated with fingerprint magnetic powder. For example, the victim assures that the piece of paper he left on the table lies differently. The expert will remove it as evidence with possible fingerprints and transfer it to the laboratory, where specialists will identify them using other special chemical substances. Even on the body of a person who died from mechanical strangulation, traces of the killer’s fingers can be identified.

Last year, specialists from Maxim Duka’s department conducted about 30 thousand requests for AFIS. Sometimes his colleagues spend whole days at crime scenes, because solving the crime largely depends on the quality of their work. There was a case when experts spent about two days inspecting one apartment where a triple murder took place.

Some criminals prefer to operate with gloves, mistakenly believing that this way they will not be left behind. However, papillary lines tend to protrude, and the mark will remain on the object in any case .

In the practice of capital experts, there was a case when a burglar was exposed based on traces left in the restroom, where he went to relieve himself. And one poacher, who was fishing on an industrial scale, was detained following a trail on ice that was well preserved in 30-degree frost.

Photo by Sergei Lukashov