Identification of handprints on paper. Chemical methods for detecting handprints

There are several methods for detecting fingerprints and palm prints:

Visual;

physical;

Chemical.

Visual observation is the inspection of an object (with the naked eye or through a magnifying glass) in obliquely incident light, i.e. at different angles of incidence of light, in the rays of which the surface of the object being examined is studied. The technique is aimed at creating a light contrast between the sweat-fat trace and the object, since a smooth surface reflects light in a specular (directional) manner, while the sweat-fat substance scatters it. In this case, the trace acquires a matte shade and becomes visible. When inspecting large surfaces, a portable light source is used. The source of light and the eye of the observer must be on opposite sides of the perpendicular, mentally restored to the plane of the trace.

Handprints on transparent objects are easier to detect when examining them through the light, using a directed beam of light from an electric flashlight, sun rays, daylight, etc. To search for hardly visible traces, bright directional light sources are used. Hardly visible colored traces of papillary patterns can be detected when illuminated by a strong light source using light filters.

This method is simple, publicly available and is used when applying other methods for detecting handprints.

Physical methods for detecting fingerprints are based on adhesive (sticking) or adsorption (absorbing) properties of the trace-forming substance. In the first case, the coloring of the trace occurs due to the deposition of the smallest particles of the dye on its substance, in the second - due to their introduction into the substance of the trace.

One of the simplest and most convenient physical reagents are powders. The stickiness of the sweat-fatty substance usually exceeds the stickiness of the receptive surface, and because of this, the sweat-fatty substance retains the powder deposited on its surface, as a result of which the coloring of the trace in the color of the powder is achieved. The effectiveness of the use of powders depends on factors such as the age of the trace, the dustiness of the surface and other conditions. The method consists in staining the fingerprints with various powders. When detecting traces with powders, it is impossible to process an object whose surface is moistened, covered with grease, fresh paint and other similar substances. The effectiveness of staining traces with powders depends on the type and structure of the powders used, the size of the particles, their configuration, specific gravity and humidity.

Requirements for powders:

Fineness from 70 to 100 microns;

The powder should not form lumps and not have foreign inclusions;

When self-compiling fingerprint powder from various components, they must be thoroughly mixed.

When staining traces, the following rules are observed:

The applied powder must be dry, fine-grained and different from the color of the treated surface;

Before applying the powder to the trace to be detected, it is desirable to stain with this powder an experimental fingerprint left on the same or similar surface;

After copying the inked trace on the fingerprint film (sticky film material), it is re-treated with powder, this treatment sometimes gives better results than the first.

The powder is applied to the trace with a fingerprint or magnetic brush, air spray, rolling over the surface and spraying under special conditions. For applying non-magnetic powders, as a rule, a fingerprint brush is used. When processing surfaces with metallized powders, a magnetic brush is used. A magnetic brush has advantages over a fingerprint brush in detecting traces of papillary patterns on fabrics and other rough surfaces.

A magnetic brush reveals traces left on objects made of a wide variety of materials, with the exception of those with magnetic properties (iron, steel, etc.) and not covered with paint or enamel. To work with a magnetic brush, colored magnetic powders are used, which have the code names "Opal", "Topaz" (white), "Ruby", "Garnet" (red-brown), "Sapphire", "Agate" (black), "Malachite » (dark brown), magnetic fingerprint powders (pmd) black, PMD-B - white. They are a mixture of metal powder with various dyes. These powders give good results in detecting long-term traces (up to 30 days) and on various trace-receiving surfaces (glass, polystyrene, paper, brass, porcelain, plywood, polyethylene, etc.).

Air sprayers (such as powder blowers) are used when a fingerprint or magnetic brush can lead to the destruction of traces that can be detected. When using sprayers, it is necessary to ensure that the powder is evenly deposited on the surface to be treated.

On flat surfaces (standard paper) traces of papillary patterns can be detected by rolling powder particles over the surface. After staining traces, excess powder is removed by shaking.

The traces of fingers and palms of the hands painted with powders are copied onto a fingerprint film, sticky film material or using a trace copying composition in an aerosol package of the "Copy" type. The tape with copied traces is packed in an envelope or sewn to the edge of a cardboard sheet. The ends of the threads are displayed on cardboard and sealed. An explanatory inscription is made on the cardboard, and the signatures of the investigator, witnesses and a forensic specialist, if he took part in the seizure of traces, are put.

On surfaces such as metal, marble, plastic, etc., colorless traces can be painted by applying the soot obtained by burning highly smoky substances. The object intended for fumigation is placed in the upper third of the black part of the flame, where the intensive upward movement of soot begins to slow down. Traces are painted with fine-grained soot, which is formed during the combustion of polystyrene foam, camphor, naphthalene.

The traces of the fingers found are removed, if possible, together with the object on which they are located or part of it and stored in conditions that protect the traces from external influences. However, traces often remain on objects that cannot be removed entirely or from which a part with a trace cannot be separated (for example: furniture, piano, safe, etc.). There may also be cases where the properties of the perceiving object or trace are such that the trace can quickly disappear, even if it is removed and protected from damage (for example: a three-dimensional trace on butter or sweat marks on paper). In all these cases, traces must be fixed.

Fumigation with iodine vapor is based on the ability of iodine to sublimate when heated. When fumigating with iodine vapor a surface on which there is a fingerprint, iodine crystallizes first of all in the areas covered with sweat-fat substance, and thus the trace is visualized.

The identified traces are immediately photographed, since as the iodine evaporates, they become invisible. The advantage of this technique is that it can be used repeatedly. Developed traces are fixed by treatment with carbonyl iron powder.

Identification of traces of hands on the skin of a corpse: from a distance of 20-50 mm, the skin of a corpse at the place of the alleged location of the traces is treated with iodine vapor and applied at the place of darkening for 1-2 seconds. silver plate with a thickness of about 0.25 mm and an area of ​​51 square meters. mm. After that, the trace is displayed in the light. There are positive examples of this method, but it has not been fully investigated.

The method of thermal vacuum deposition is based on the deposition of heavy metals (tungsten, molybdenum) in a vacuum. This colorizes the background. In practice, there are cases of detecting traces in this way even on a sheet of slate.

There is also a method using liquid dyes, such as ink solutions. In this case, the object with a trace is dipped into a bath with a solution and then placed in running water.

Chemical methods are based on the chemical interaction of specially prepared solutions with elements of the sweat-fat substance. These methods are used to identify handprints on paper, cardboard, wood of various prescriptions (in some cases up to several years) when the methods described above did not give positive results. It is used most often in the laboratory.

Among the chemical methods for detecting fingerprints, the following are distinguished:

1) detection of handprints using a solution of silver nitrate in distilled water.

A 0.5-10% solution of silver nitrate in distilled water (“lapis”) is prepared and an object with traces is processed using a cotton swab or spray gun. After that, it is dried in the dark, otherwise the background is abundantly colored and manifested under the influence of sunlight, or with the help of UV illuminators. When developing, visual control is required.

If traces of great prescription are detected, then the concentration of the solution is doubled.

b) identification of traces of hands using a solution of ninhydrin or alloxan in acetone.

A 1% solution is used, applied in a similar way, dried under a hairdryer or a hot electric stove. At the same time, the traces treated with ninhydrin turn blue-violet, and the traces treated with alloxan - in an orange trace. Alloxan is cheaper, and the traces treated with it have a bright crimson glow in UV rays. Traces appear from 2 hours to 1-2 days. Therefore, for operational purposes, the express method is used:

The prepared solution is applied in a similar way and after the acetone has evaporated, the surface is abundantly wetted with a 1% solution of copper nitrate in acetone, and then immediately subjected to intensive heat treatment. To do this, the object under study is covered with a sheet of paper and a hot iron is passed over it with an iron (laid in a glossy, held over an electric stove). The traces appear immediately, are strong enough and the coloring of the background does not occur. The disadvantage is the dotted image of papillary lines in the patterns.

After ninhydrin treatment with silver nitrate is possible.

d) detection of blood traces of hands.

To do this, use a solution of benzidine in alcohol and hydrogen peroxide (5 parts of a 1% solution of benzidine in alcohol and 1 part of a three percent hydrogen peroxide). Blood traces treated with this solution turn blue-green. The color is stable and does not require additional fixing.

In order to detect fingerprints at a crime scene, you need to know where and how to look. When examining the scene of the incident, the investigator must imagine what exactly the criminal was doing at the scene of the crime, what objects he took in his hands, which he touched. All this is necessary in order to decide which subjects to study.

Together with the investigators, specialists who are employees of the forensic divisions are engaged in the search for traces of hands. Alekseev A.I. The practice of criminal investigation. Scientific and practical collection / A.I. Alekseev. - M.: Liga Mind, 2005. - S. 94.

Successful search for traces of fingers primarily depends on the solution of organizational issues of preparation for the inspection of the scene and its production. There are a number of recommendations for detecting handprints at the scene of an accident:

• 1. Employees of the forensic subdivisions of the Ministry of Internal Affairs are involved as specialists in the inspection of incident sites that require the use of forensic tools and methods to detect, fix and seize traces and other material evidence.
• 2. When inspecting the scene of an incident that occupies a large area, it is advisable to provide for the assistance of several forensic specialists in advance, entrusting each with a specific area of ​​work.
• 3. Measures should be taken to protect the scene of the incident before the arrival of the investigative team and during the inspection.
• 4. A forensic specialist is obliged to take with him and use during the inspection the necessary scientific and technical means designed to identify, fix and seize objects that may be of evidentiary value.
• 5. Arriving at the scene, the investigator and forensic specialist must clarify the previously received information about the crime. Without changing the original situation, the forensic specialist makes an orienting overview photography.
• 6. Further, the investigator and the forensic specialist get acquainted with the scene of the incident, agree on the content and sequence of their actions.
• 7. Based on the information obtained during the preparatory work, areas are determined where handprints were most likely to be left.

Places where traces of hands and objects with which the criminal came into contact can be left are established in the process of studying the situation and based on the results of finding other traces.

The objects on which to search for traces of hands are largely determined by the type of crime committed and the possible actions of the offender and the victim.

Often, handprints are found on objects that the offender, for various reasons, took away from the crime scene and left at some distance from him. Be sure to inspect objects that do not fit into the situation of the scene.

In the process of interrogations, confrontations and other investigative actions, when the details of the event are clarified, the behavior of persons at the scene of the crime, information may appear that contributes to the detection of handprints, in this case a second examination is carried out. Anyukov M.S. Fundamentals of legal regulation of operational-investigative activities / M.S. Anyukov. - M.: ABC Firm, 2005. - S. 102.

In order not to leave traces of hands, criminals take various precautions - they wear gloves, use handkerchiefs, wipe the surfaces of objects they come into contact with.

If the offender used gloves (leather, cloth), then the traces found can also be used to identify, first of all, gloves, but in some cases to establish some group signs of a person (examination of sweat with which gloves are impregnated, etc.).

In the traces of leather gloves, a skin pattern, wrinkles, folds, defects that have arisen during wearing are displayed. In the traces of cloth gloves, signs of fabric, type of weave, fabric defects, etc. are displayed. Particularly valuable in terms of identification are areas in the seam area, here an original convergence of the threads of two sewn pieces is formed.

When starting to work with superficial fingerprints, primarily with fat sweat marks, one should keep in mind the various circumstances that affect their safety. In fingerprinting, it is important to know the statute of limitations for leaving a trace in order to choose the right method for detecting traces of papillary lines.

A relatively short period of limitation is calculated from several hours to 30 days, the average period is from 30 to 180 days, and the long period of limitation is more than 180 days.

Sweat marks of fingers are well preserved on surfaces that do not absorb moisture: on glass, some plastics, porcelain, glazed surfaces, polished wood and others. On paper, cardboard and objects covered with oil paint, etc. sweat marks usually remain worse.

Modern forensics offers the following methods for detecting and identifying handprints.

Physical methods:

1. The visual method of detecting sweat marks depends on the optimal combination of lighting and observation. Traces on smooth glossy surfaces can be detected due to the fact that the beam of light from the substance of the trace is reflected, scattered, and directed from the background. The room in which the inspection is carried out, it is desirable to darken a little.

The light source is located on the opposite side from the observer. An angle of illumination is selected at which the trace is most noticeable.

2. Powder staining method. This method can reveal relatively fresh marks on both smooth and rough surfaces.

Depending on the color and adhesive properties of the trace-receiving surface, powders are used that differ in color, structure and specific gravity.

For pollination of fat traces, they are used as universal mixtures (cobalt oxide - 60%, rosin - 37%, rhodamine - 3%; to detect traces on dark surfaces - lead oxide - 60%, rosin - 37%, zinc oxide - 3%), and single-component powders.

So, zinc oxide - a white powder - gives good results in detecting marks on plastics, varnished surfaces, rubber, leatherette, marble, glass. Copper oxide - a black powder - is used to detect marks on paper and surfaces painted with oil paint. Aluminum powder shows marks well on glass and other high-gloss surfaces. Graphite is used to reveal traces on paper. Lead oxide - orange powder - is used to detect traces on rubber, cardboard, plywood. Reduced iron - gray-brown powder - allows you to detect traces on any surfaces that do not have magnetic properties. Ivanov A.O. Ways and fates of domestic criminalistics / A.O. Ivanov. - M.: INFRA-M, 2008. - S. 56.

The pollination technique depends on the properties of the powder and the trace-receiving surface.

The easiest way is to sprinkle powder on the surface to be treated, followed by shaking off the excess. This technique is used when processing sheets of paper with powders.

The fingerprint brush is used when processing hard smooth surfaces. Rubber bulbs, medical powder blowers and other sprayers are used to apply powder to hard, rough surfaces. The magnetic brush is used to treat surfaces with reduced iron powder.

Fingerprints identified by powders are removed by copying them onto a fingerprint film (in cases where the traces found cannot be removed with the object or part of it).

Physical and chemical methods:

1. It is possible to fumigate handprints with crystalline iodine vapor using an “iodine” tube, followed by photographing the colored trace or copying it onto a silicone film from a polymer paste.

Back in 1888, Eber, a Berlin veterinarian, proposed to the Prussian Ministry of the Interior a method he had developed for fixing invisible fingerprints with iodine. The iodograms made by him have survived to this day, although the technique for making them has remained unknown.

The process of processing fingerprints with iodine vapor directly at the scene can still be difficult.

Difficulties arise for those who do not know how to photograph developed prints well enough, and therefore are not able to save them, because they quickly disappear. In this case, the same iodine helps, but already used in the form of a powder. For this purpose, iodine crystals are turned into powder and mixed with dry potato flour in a ratio of 1:10. The application process is the same as with graphite. The staining of invisible prints occurs even somewhat faster than with the action of iodine vapor. After some time, the imprint identified in this way will disappear, so it should be fixed either photographically or by ink processing.

2. Dumping is used to reveal invisible old traces of hands, as well as traces left on the surfaces of objects made of tinplate, aluminum, marble, and certain types of plastics. Dumping as a way of working with handprints is not widely used, because. its use has a certain risk of loss of traces, requires skill and is acceptable mainly in laboratory conditions.

Pilling treatment is carried out by burning substances such as camphor, naphthalene, etc. The sweat-fat substance of the trace is slightly warmed up under the action of the flame, and the soot particles are well introduced into it. The resulting trace is painted with a kind of caked crust. It is necessary to ensure that there are no impurities in the combustible substance, as they can give coarse soot.

Chemical methods:

The most common solution of ninhydrin in acetone and the solution of alloxan in acetone.

1. A solution of ninhydrin in acetone is used to treat sweat marks of fingers, palms, and is characterized by high sensitivity. Amino acids and protein substances of the trace, reacting with ninhydrin, do not penetrate deep into the material on which traces are left. Therefore, favorable conditions are created for the detection of sweat-fat traces from several months to several years ago. There is information about the detection of traces of papillary lines with the help of ninhydrin up to 30-32 years old. With the help of a solution of ninhydrin, handprints are detected on many grades of paper, except for those that contain glue of organic origin (casein and animal). The main materials on which handprints are detected with ninhydrin are paper and cardboard. Positive results are also achieved when ninhydrin is used to treat fat and sweat marks left on plywood, planed wood. Commentary on the Criminal Code of the Russian Federation / Ed. A.V. Naumov. - M.: INFRA-M, 2005. - S. 61.

Ninhydrin dissolves in acetone. Experiments have shown that a 0.8% solution of ninhydrin can be used for the successful development of prints. This solution is almost colorless and evaporates quickly. One method of developing in this way is to place the paper to be examined on a filter paper base. A swab of cotton wool soaked in a solution of ninhydrin in acetone, twice, over and over again, cover the surface of the document under study.

The solution should penetrate to the back of the paper, which is easily achieved if the paper is not too thick. After a certain period of time, an invisible fingerprint appears on the white surface of the paper, which has a purple color. The development time depends mainly on the temperature. Under particularly favorable conditions, the imprint can appear in as little as 30 minutes. However, this usually takes much longer (a day or more).

2. A solution of alloxan in acetone is used to detect handprints on paper that are less than 9 days old. The solution is applied with a cotton swab to the surface on which handprints are searched. The detection process lasts from 2 to 28 hours.

After processing, the object with traces is kept in the light for 3-4 hours, then it is placed in a light-tight chamber.

Prints on wood are also quite common, but it is much more difficult to identify them than on paper or glass. The only exception is wood with a polished or lacquered surface.

Depending on the color of the surface, prints on wood can be detected using zinc oxide with rosin, white lead. On unpainted wood and on plywood, prints appear quite successfully when stained with nitric acid silver.

1. History of the development of forensic identification p.2

2. Structure and properties of papillary patterns of human hands p.4

3. General and particular signs of papillary patterns p.6

4. Types of handprints p.9

5. Rules and methods for detecting handprints p.10

List of used literature p.14

I. The history of the development of forensic identification.

The founder of forensic identification is

Alfonso Bertillon is a police file clerk, the son of a respected statistician and vice-president of the Anthropological Society of Paris. What was his identification based on? He used the scientific data of anthropology and statistics, according to which the dimensions of the body of one person never completely coincide with the dimensions of the body of another. He measured criminals (9 measurements: height, arm span, chest width, chest length, head width, left foot length, middle finger left hand, left ear) entered the body measurements into cards and thus got the opportunity to recognize those already registered. The process itself was very complex and time-consuming, but the most progressive at that time. The beginning of the procession of Bertillonage in Europe dates back to 1981. The methods of identification that existed before him consisted only in the use of primitive forms of verbal portraits and the recognition of criminals. For this, "parades" of criminals were used, during which police officers were present and remembered them. Photography came to the aid of the police and the basic rules for photographing criminals were developed just by Bertillon.

In parallel with Bertillonage, fingerprinting also made its way to life:

William Herschel, an employee of the colonial inspection in India, studied the possibilities of identification using fingerprints, proved that they do not change throughout life.

Francis Galton is one of the outstanding English experts in the field of anthropometry, one of the first in London who drew the attention of specialists to the advantages of fingerprinting over bertillonage.

Edward Henry, Inspector General of Police in Bengal, created an acceptable fingerprint registration system, which is practically the basis of the ten-finger system, according to which fingerprint records are kept in the country's ATC Information Center. In 1901, when he became president of the London Police, he replaced bertillonage with fingerprinting.

It should also be noted that Juan Vuchetich, an Argentine police officer, who created a workable fingerprint registration system a few years earlier and it was adopted by the police of South American countries.

1914 - the year of the death of Bertillon was the last year of the existence of Bertillonage and the final victory of fingerprinting.

In Russia, in 1923, the Galton-Henry system was somewhat changed, supplemented by the existing one in pre-revolutionary Russia and adopted in the USSR.

II. The structure and properties of papillary patterns of human hands.

The human skin consists of two main layers: the outer (epidermis) and the skin itself (dermis). Actually the skin or dermis has two layers: mesh and papillary. The last of them has the form of elevations, the height of which is different in different parts of the skin of the body. On some parts of the body, they do not protrude to the surface of the skin (smooth skin), while on others they form linear elevations in the form of scallops (papillary lines), the distance between which is from 0.4 to 1.2 mm. Such lines cover the palms and feet of a person, on which papillary patterns are formed.

Consider now the structure of the papillary pattern of the human hand. On a sheet of paper (on a blackboard with chalk), draw a hand and mark on it the zones of the papillary pattern:

1-5 - nail phalanges of the fingers;

6-9 - middle phalanges of the fingers;

10-14 - the main phalanges of the fingers;

Tenar No. 1 - a hill on the palmar surface of the hand at the thumb;

Tenar No. 2-No. 4 - subdigital areas of the palmar surface of the hand;

Hypotenar - the area on the side of the edge of the palm.

The plantar part of the foot is characterized by 4 zones:

Finger;

Metatarsal;

Intermediate (vault);

Heel.

On the nail phalanges of the fingers, traces of which are most often found in expert practice, the following zones of the papillary pattern are distinguished:

Central;

Upper (distal);

Lower (basic);

Right or left (right lateral or left lateral).

This classification of areas of papillary patterns will be used in the future when describing handprints in the WMD protocols, when describing handprints in expert opinions.

The main properties of papillary hand patterns in terms of identification are individuality, relative immutability,

recoverability.

Individuality - lies in the fact that not only in different faces, but also on different fingers (palmar surfaces) of the same person, papillary patterns are different.

Relative immutability (stability) - lies in the fact that throughout life, as a rule, the structure of the papillary pattern remains unchanged, only its size increases.

Restorability - in case of damage to skin areas with papillary patterns, they can restore their original appearance if the papillary layer is not damaged.

The above properties of papillary patterns made it possible to successfully use handprints in the investigation and detection of crimes.

III. General and particular signs of papillary patterns

Common features that characterize papillary patterns include:

1. Type and type of papillary pattern.

3. The number of papillary lines in individual areas

papillary pattern.

4. The relative position of the parts or elements of the pattern.

5. The size of the pattern.

Pattern types: arc, loop and swirl

Types of patterns:

a) arc: - simple

(5%) - pyramidal

Tent

spruce

With an indefinite structure of the center.

b) loop: (papillary lines starting at one edge and not reaching

(65%) of the other bend sharply, forming parallel loops)

Simple

curved hinges

- "racket loops"

Half loops

parallel loops

Counter loops.

If in an arc pattern two flows form a pattern, then in a loop

there are three of them. The point where the three streams of papillary lines converge is called the delta.

c) curled: (papillary lines form a pattern inside the pattern in the form

(30%) ovals, circles, spirals, etc.)

Simple (circles, ovals)

Spirals

Loops - spirals

Loops - balls

Incomplete curl patterns

It should be borne in mind that there are also transitional types of patterns, which include elements of various types of patterns.

There are also abnormal papillary patterns in which the pattern is not visible.

Types and types of patterns, as well as other of the above features, refer to common features that may belong to different individuals.

The identification significance of papillary patterns is formed by private signs, which are divided into the following groups:

Signs of papillary patterns;

Signs of papillary lines;

Details of the structure of the microrelief of lines;

Other signs of patterns.

a) signs of papillary patterns:

Beginnings and endings of lines;

Merging and bifurcation of lines;

Peephole, hook;

Fragment;

Point (less than 1.5 S papillary line);

Thin lines.

b) signs of papillary lines:

Line bend;

Line break;

Thickening or narrowing of the line;

Line break.

c) signs of microrelief are classified into two groups:

Poroscopic, which take into account the shape, size and

interposition of pores (sweat glands);

Edgeoscopic, which take into account signs of contours

papillary lines in the form of protrusions, depressions, etc..

d) other signs:

scars; the presence of a scar is a general sign, and its details are private

signs;

Flexor lines, folds, wrinkles - are displayed as wide and narrow white stripes of an arched or sinuous shape.

The identification significance of particular features is determined by the frequency of their occurrence. So the beginnings and ends of papillary lines are found 20-25 times more often than breaks, hooks, or eyes, 25 times more often than bridges, so the identification significance of the latter is higher. So we come to one of the controversial issues in expert practice: "How many signs do you need to see in the trace in order to remove it from the scene?" The answer to this question is influenced by many factors: the clarity of the display of lines in the trace, the size of the trace, the possibility of localizing the part of the hand with which it was left, the identification significance of signs and their number. The most common is the judgment that there should be at least 10 of them.

IV. Types of handprints

Handprints, depending on the mechanism of formation, can be voluminous and superficial, colored and colorless, hardly visible and invisible.

Volumetric traces are formed as a result of contact of hands with a plastic surface (butter, cheese, plasticine, a burning candle, icy surfaces, etc.).

Surface marks are formed on hard surfaces due to delamination or layering of a trace-forming substance. A delamination trace is formed as a result of adherence of trace-carrier particles to the surface of the hands, and a layering trace is formed as a result of the transfer of any particles from the surface of the hand (sweating substance, blood, dyes, etc.) to the trace-receiving surface. Surface traces can be colorless and colored, barely visible or invisible.

V. Rules and methods for detecting handprints

1. Before detecting handprints, measures must be taken to ensure that during the search not to destroy other traces present on the objects or to impede their further study (footprints on the floor, microfibers on the window frame, traces of biological origin, etc.).

2. Objects with traces should be taken in such a way that they do not leave their traces and do not destroy the traces of the criminal.

3. When detecting traces, it is first necessary to use visual detection methods, and then physical and chemical ones.

4. Avoid exposure to objects with traces of hands of a sharp temperature drop.

5. First of all, traces are detected on objects that may be exposed to precipitation, thermal effects, mechanical damage, etc.

Ways to detect handprints:

1. Optical (visual) - for voluminous, colored or barely visible traces. This method is based on enhancing contrast by creating favorable lighting and observation conditions.

These include:

Illumination of a surface at a certain angle or inspection of a given surface from various angles;

Viewing transparent objects against the light;

Inspection of the surface using a laser, sources of UV rays, using light filters.

This method is simple, publicly available and is used when applying other methods for detecting handprints.

2. Physical methods - based on adhesive (sticking) or adsorption (embedding) properties of a trace-forming substance, a trace-receiving surface or a material used to detect.

These include:

a) the method using fingerprint powders is the most common in expert practice.

Requirements for powders:

Fineness from 70 to 100 microns;

The powder should not form lumps and not have foreign inclusions;

When self-compiling fingerprint powder from various components, they must be thoroughly mixed.

Powders are applied with a brush, powder blowers, rolling over a trace-receiving surface.

b) using iodine vapor with fixing with reduced iron powder.

Identification of traces of hands on the skin of a corpse: from a distance of 20-50 mm, the skin of a corpse at the place of the alleged location of the traces is treated with iodine vapor and applied at the place of darkening for 1-2 seconds. a silver plate with a thickness of about 0.25 mm and an area of ​​51 sq. mm. After that, the trace is displayed in the light. There are positive examples of this method, but it has not been fully investigated.

c) the method of thermal vacuum deposition - based on the deposition of heavy metals (tungsten, molybdenum) in a vacuum. This colorizes the background.

In practice, there are cases of detecting traces in this way even on a sheet of slate.

d) a method based on the use of radioactive isotopes -

It consists in the treatment of surfaces of objects with radioactive materials.

e) dipping with flame soot - used to detect handprints on polished metal surfaces. Its essence is as follows: when burning individual objects (for example, casts made using K paste, polystyrene foam), soot is abundantly released, which is a fine powder, which is used to identify handprints.

e) using liquid dyes, such as ink solutions.

In this case, the object with a trace is dipped into a bath with a solution and then placed in running water.

3. Chemical methods - are based on the chemical interaction of specially prepared solutions with elements of the sweat-fat substance.

These methods are used to identify handprints on paper, cardboard, wood of various prescriptions (in some cases up to several years) and are most often used in laboratory conditions.

a) detection of handprints using a solution of silver nitrate in distilled water:

A 0.5-10% solution of silver nitrate in distilled water ("lapis") is prepared and an object with traces is processed using a cotton swab or spray gun. After that, it is dried in the dark, otherwise the background is abundantly colored and manifested under the influence of sunlight, or with the help of UV illuminators. When developing, visual control is required. The best results according to the Volgograd Higher School of the Ministry of Internal Affairs were obtained with the following solution:

Distilled water - 100 ml.

Silver nitrate - 1 gram.

Citric acid - 0.2 grams

Tartaric acid - 0.1 grams

Nitric acid - 3-5 drops.

If traces of great prescription are detected, then the concentration of the solution is doubled.

b) detection of handprints using ninhydrin solution

or alloxan in acetone:

A 1% solution is used, applied in a similar way, dried under a hairdryer or a hot electric stove. At the same time, the traces treated with ninhydrin turn blue-violet, and the traces treated with alloxan - in an orange trace. Alloxan is cheaper, and the traces treated with it have a bright crimson glow in UV rays. Traces appear from 2 hours to 1-2 days. Therefore, for operational purposes, the express method is used:

The prepared solution is applied in a similar way and after the acetone has evaporated, the surface is abundantly wetted with a 1% solution of copper nitrate in acetone, and then immediately subjected to intensive heat treatment. To do this, the object under study is covered with a sheet of paper and a hot iron is passed over it (placed in a glossy, held over an electric stove). The traces appear immediately, are strong enough and the coloring of the background does not occur. The disadvantage is the dotted image of papillary lines in the patterns.

After ninhydrin treatment with silver nitrate is possible.

d) detection of blood traces of hands - for this, a solution of benzidine in alcohol and hydrogen peroxide are used (5 parts of a 1% solution of benzidine in alcohol and 1 part of three percent hydrogen peroxide. Blood traces treated with this solution turn blue-green. The color is stable and additional does not require fastening.

2006 Contents 1. Traces hands 2. Views traces hands 3. Detection, fixation and withdrawal traces hands 4. Literature 1. Traces hands Most successfully ... substances can detect bulk traces hands. Methods identifying traces hands depends on the mechanism...

Traces in forensics, their classification and use in the detection and investigation of crimes

Abstract >> State and Law

To ways identifying traces hands include: visual, physical and chemical. Visual ways identifying traces hands is a discovery traces at ... component. Chemical reagents used for identifying traces hands, is a 1.5 - 2% solution ...

Study traces human feet at the scene

Abstract >> State and Law

ways identifying traces shoes. 2.3. The physical and chemical methods are the same as for identifying traces hands. Methods ... fixation and withdrawal traces shoes. Requirements for the packaging of items with traces. Description traces ...

Kinds traces human

Abstract >> State and Law

... traces, identified iodine vapor, by copying onto starch iodine or iododextrin films. If a traces hands... component. Chemical reagents used for identifying traces hands, this is a 1.5-2% solution of ninhydrin or ...

Detection of traces of hands is carried out in several ways. Volumetric traces are detected using oblique illumination due to the shadow contrast of the depressions formed by papillary lines. Surface colored traces are easy to detect in diffused light. If the color of the dye matches the color of the background, it is necessary to select an appropriate light filter or use a source of ultraviolet rays, or use an electron-optical converter in the infrared zone of the spectrum.

The greatest difficulty is the detection of fat traces. The choice of one or another method of their detection depends on the nature of the trace-perceiving surface and the prescription of leaving a trace. Traces on smooth glare surfaces are detected visually. The effectiveness of this method depends on the optimal combination of illumination and observation. Relatively fresh marks, both on smooth and rough surfaces, can be detected by powder staining.

Depending on the color and adhesive properties of the trace-receiving surface, powders are used that differ in color, structure and specific gravity. Some sets of scientific and technical tools include universal powders "Sapphire" and "Ruby", which give satisfactory results when processing traces on surfaces of various degrees of roughness. "Sapphire" is a light universal mixture and is recommended for revealing marks on dark surfaces. To detect traces on light surfaces, a dark universal mixture "Ruby" is used. One-component powders are also used for pollination of sweat marks. So, zinc oxide, a white powder, gives good results in detecting marks on plastics, varnished surfaces, rubber, leatherette, glass. Copper oxide, a black powder, is used to detect marks on paper and surfaces painted with oil paint. Aluminum powder shows marks well on glass and other high-gloss surfaces. Graphite is used to reveal traces on paper. Lead oxide, orange powder, is used to detect traces on rubber, cardboard, plywood. Reduced iron, a gray-brown powder, reveals traces on any non-magnetic surfaces.

The pollination technique depends on the properties of the powder and the trace-receiving surface. The easiest way is to sprinkle powder on the surface to be treated, followed by shaking off the excess amount. This is how sheets of paper are processed. The fingerprint brush is used when processing hard smooth surfaces. Rubber bulbs, medical powder blowers and other sprayers are used to apply powder to hard, rough surfaces. The so-called magnetic brush (a magnetized metal rod enclosed in a plastic case) is used to treat surfaces with reduced iron powder. Fingerprints identified by powders are removed by copying them onto a fingerprint film. Surface treatment with powders, followed by copying of traces on a dactyl film, is carried out only in cases where the trace cannot be visually detected or it is impossible to remove the visually detected trace with the object or its part.

Staining traces with iodine vapor is a physical method. With the help of iodine vapor, traces appear on paper, wood, plywood, surfaces whitewashed with lime or painted with oil paint.

There are several ways to fix traces stained with iodine:

• 1) The traces revealed by iodine vapor are photographed according to the rules of detailed shooting;
• 2) Traces stained with iodine vapor are additionally dusted with reduced iron powder. (In this case, iron iodide is formed, the trace acquires a persistent dark brown color and is firmly held on the trace-receptive surface);
• 3) A piece of photographic material moistened with distilled water is pressed tightly against the trace fumigated with iodine. Then the photographic film or photographic paper is exposed to light, fixed, washed and dried. In this case, the image is obtained due to the fact that iodine acts as an attenuator at the points of contact with the photo-emulsion layer.

Chemical methods for detecting invisible sweat-fat traces are based on the ability of some components of the sweat-fat substance to enter into a color reaction with such chemical reagents as silver nitrate, ninhydrin and alloxan. Silver nitrate is used as a 1% solution in distilled water. After applying the solution with a cotton swab, the object is exposed to bright sunlight or placed under a mercury-quartz lamp without a filter. Under the action of ultraviolet rays, the silver chloride formed as a result of the reaction between silver nitrate and the chloride salts of the sweat-fatty substance turns into a metallic one, which paints the trace black. Ninhydrin and alloxan enter into a color reaction with protein breakdown products that are part of the sweat fat substance. They are used in the form of a one percent solution in acetone. Under the influence of heat, ninhydrin stains the trace in purple, alloxan in orange. The traces revealed by chemical methods are fixed by photographing. The seized traces and comparative samples - prints of papillary patterns of the persons being checked are sent for fingerprint examination for the purpose of identification. Depending on which parts of the skin surface left the traces sent for examination, prints of the palms or prints of all ten fingers are made on clean sheets of paper with printing ink. Under each print, a record is made with which hand and which finger it was made. The sheets indicate who left the comparative prints, and the signature of the person being checked is put. If the person being checked was previously registered with fingerprints, then his fingerprint card can be presented for comparison. Sweat, painted or voluminous finger prints, the belonging of which is known to a certain person, can be used as comparative samples.

The need to use such samples arises when it is impossible to obtain special comparative samples or when there is no fingerprint of the person being checked. The safety of traces sent for examination is ensured by their proper packaging. Traces of hands taken directly from the trace-receiving object are packed in such a way that the traces do not come into contact with the walls of the package. It is strictly forbidden to wrap unprotected items in soft packaging material. Eisman A.A., Expert opinion. Structure and scientific justification. M., 1967

The given information about handprints, their identification and study show that work with them begins at the very initial stages of detecting and investigating crimes. At the same time, great importance is attached to the knowledge and skills that both the investigator and the interrogating officer, who are the first to “contact” with the traces of a person, should possess. The effectiveness of the investigation and proof of guilt depends on their ability to identify, preserve and correctly remove traces.

2.4.3 Chemical methods for detecting handprints

Developed on the basis of the chemical method, the methods for detecting handprints on various surfaces are based on the ability of some chemical compounds in certain ratios and conditions to enter into irreversible chemical reactions with amino acids and nitrogenous bases that are part of the sweat-fatty substance that forms the trace. A feature of this process is the formation of colored reaction products due to the introduction of chromoform groups into the composition of the molecules of the compounds of the sweat-fatty substance, which provide selective absorption of light. As a result of rather complex processes that occur during the course of such reactions, the resulting products lead to the appearance of traces formed by the sweat-fat component.

The most widespread in expert practice are the following methods for detecting handprints: based on ninhydrin (0.5-1% solution in acetone); alloxan (0.5-1%) solution in acetone); 0.5-2%) solutions of silver nitrate in distilled water.

An aqueous solution of silver nitrate (lapis) reacts with the chlorides that are part of the trace fatty substance. The resulting silver stains the papillary lines.

The process is photochemical in nature. Silver nitrate, usually 5%, is used to treat marks left on paper, cardboard, plywood, and wood. The solution is usually applied to the surface with the alleged traces with a cotton swab, then the treated object is dried and then exposed to sunlight or ultraviolet radiation, which greatly accelerates the process of manifestation of papillary lines.

The use of silver nitrate excludes the subsequent biomedical study of the sweat-fatty substance of the trace. After such processing, a technical and forensic examination of documents is also practically impossible, since the surface of the paper is covered with dark spots.

It should be noted that a solution of silver nitrate reveals traces of fingers that are no more than 6 months old.

A solution of ninhydrin in acetone is used to treat sweat marks of fingers, palms, and is distinguished by its high sensitivity. Amino acids and protein substances of the trace, reacting with ninhydrin, do not penetrate deep into the material on which traces are left. Therefore, favorable conditions are created for the detection of sweat-fat traces from several months to several years ago. With the help of a ninhydrin solution, handprints are detected on many grades of paper, except for those that contain glue of organic origin. The main materials on which handprints are detected with ninhydrin are paper and cardboard. Positive results are also achieved when ninhydrin is used to treat fat and sweat marks left on plywood, planed wood.

When treated with ninhydrin, old traces appear more clearly than fresh ones.

Ninhydrin solution, usually 0.2-; 0.8-; one-; 2-; 5%, applied with a cotton swab, brush or spray gun to the surface where hand marks are suspected. The detection process depends on many factors, primarily temperature. It usually starts after 3-4 hours and ends after 5-6 hours. In some cases, this procedure is delayed up to 3 days or more. To speed up the process of identifying traces, an object with traces is heated by ironing, or placed near heating appliances. When heated, papillary lines appear after a few minutes and even seconds. This solution stains the sweat-fat substance in a pink-violet color.

A solution of alloxan in acetone is used to detect handprints on paper that are less than 9 days old. The solution is applied with a cotton swab to the surface on which fingerprints are searched. The detection process takes 2-28 hours.

After processing, the object with traces is kept in the light for 3-4 hours, then it is placed in a light-tight chamber. This solution stains the sweat-fat substance in color from orange to red. The revealed traces in UFL give a bright crimson luminescence.

In addition to the chemical methods listed above for identifying the sweat-fatty substance of the trace, others are also used:

Benzidine with hydrogen peroxide - a two-solution composition (0.1% solution of benzidine in alcohol and 3% hydrogen peroxide solution) in a ratio of 5:1. used to color faintly visible and invisible traces formed by blood blue.

Leucomalachite greens and glacial acetic acid (greens -1 g, ether - 50 ml, acid - 10 drops, hydrogen peroxide - 2-3 drops). Used for the same purposes as benzidine, but turns traces green.

Ortholidin - actively reacts with amino acids and nitrogen compounds of the sweat-fat substance through an intermediate reaction with iodine, which was introduced into it during the processing of the object and fixes the trace. Traces are painted blue or purple.

8 - hydroxyquinoline - (solution in acetone or chromoform) reacts to amino acids, exciting yellow-green fluorescence in UV light. Gives good results in detecting handprints on foam, aluminum, painted or varnished surfaces, paper, synthetic film, artificial leather.

Salt solutions in distilled water. Used to detect traces on metal surfaces:

1 - 2% solution of copper sulphate - on iron alloy products (light traces on a dark background);

1 - 2% solution of acetic lead - on zinc products (light traces on a dark background);

0.5 - 1% solution of silver nitrate - on copper products (dark marks on a light background);

0.5% solution of gold chloride - on nickel-plated surfaces (dark marks on a light background).

Pairs of cyanoacrylates - the action is based on the reaction with amino acids and water of the sweat-fat substance, which determines the process of polymerization, staining the trace white and fixing it on the surface.

A solution of potassium permanganate with sulfuric acid is used to detect handprints on polyethylene. Its advantage lies in the fact that other methods for detecting sweat-and-fat traces of hands on polyethylene materials do not give positive results due to the presence of a static charge of electricity. The solution is prepared as follows: 4 g of potassium permanganate is dissolved in 200 ml of distilled water, after which 10 ml of sulfuric acid is added. Depending on the size of the polyethylene surface, it is processed with a cotton swab or placed in a cuvette for photographs or another container for 20–30 s. The process of revealing papillary lines is quite intensive, and the trace becomes dark brown.

Thus, it is not recommended to use chemical agents during the inspection of the scene, as they change the initial appearance of the object.

Thus, on the basis of the analysis of special and reference literature, this chapter discusses the concept of traces in forensic science, provides a classification of traces of the palmar surface, and also considers the mechanism for the formation of this group of traces, analyzes various methods used to detect and identify traces of the palmar surface, in particular , visual-optical, physical, physico-chemical, chemical, as well as recommendations for the detection, fixation and removal of these traces.

CHAPTER 3. USE OF DIGITAL PHOTOGRAPHY IN PROCESSING DETECTED TRACES OF THE PALM SURFACE 3.1 Using black amide to reveal the pattern of papillary lines in a bloody palm mark found on tissue

Properties of black amide.

Black amide is a biological dye that stains proteins present in blood and some other body fluids. This results in blue-black spots. Black amide has been successfully used in detecting latent traces of hands stained with blood, but is ineffective in detecting traces of hands formed by ordinary sweat fat.

NA is used only after all other bodily fluids (semen, saliva, urine, blood stains for research, etc.) have been collected and after other methods of searching for fingerprints have been applied.

Black amide can be used in the examination of handwriting, ink, paper, and substances such as fibers, hair, paint, and similar evidence. Photofixation is carried out before the application of the substance.

Black amide can be used on almost any surface, porous or non-porous. However, some porous surfaces form a very strong background. Also used on the skin of the remains, but not used on the skin of a living person's body. The methanol based formula is highly flammable and toxic, damaging some surfaces. Therefore, in practical applications, the use of a formula based on water is allowed. Black amide is available in powder and premixed concentrate.

Precautionary measures.

1. When preparing and using the substance, wear protective gloves and clothing, including a protective mask.

2. HA is toxic and must be mixed in a fume hood or using a respirator.

3. It is necessary to ventilate the room well. If ventilation is insufficient, a mask with a filter cartridge made of organic material should be used.

4. The presence of smoldering materials and open flames during use is not allowed.

Black Amide is used in the form of solutions, and several types are made depending on the purpose of the application.

SOLUTIONS.

Working solution (4000 ml)

1. Pour 15 g of cha powder into a suitable cup.

2. Carefully add 400 ml of glacial acetic acid.

3. Stir until the powder is completely dissolved. It is recommended to use a magnetic stick.

4. Pour 3600 ml of methanol into a suitable sized cup. Add the pre-mixed tea and acetic acid from step 3 above. Stir for at least 30 minutes.

5. Place the solution in a clean container and close tightly.

6. Label the container with the name "A working solution" and the date it was prepared.

Pre-wash solution (4000 ml)

1. Gently pour 400 ml of glacial acetic acid into a cup.

2. Add 3600 ml of methanol. Stir with a plastic stick. A colorless solution will be obtained.

4. Label the container with the name (acetic acid solution of methanol) and the date of preparation.

Final wash solution (1000 ml)

1. Gently add 50 ml of glacial acetic acid to 950 ml of distilled water. Stir until blended.

2. Place the solution in a clean glass bottle.

Aqueous solutions - use during the inspection of the scene or in the laboratory.

Aqueous fixative solution - Solution No. 1. (1000ml)

1. Weigh out 2 g of 5-Sulfosalicylic acid. Place in a clean, dry 2 liter flask.

2. Measure out 1 liter of distilled water. Add to 5-Sulfosalicylic acid with constant stirring with a magnetic stick. You will get a clear fixing solution based on water.

3. Place the aqueous solution in a clean, dry 1-litre plastic-coated glass bottle with a tight, ground-in cap.

Aqueous working solution - Solution No. 2 (1000 ml).

1. Weigh out 2 g of HA. Place in a clean, dry 2 liter glass flask.

2. Weigh out 20 g of citric acid. Add to cha.

3. Measure out 1 liter of distilled water. Add to flask. Stir with a magnetic stick for at least 30 minutes. You will get a black-blue working solution.

4. Place the aqueous solution in a clean, dry 1-litre plastic-coated glass bottle fitted with a tight-fitting lid.

Laboratory Primary Wash Solution.

1. Carefully pour 100 ml of glacial acetic acid into a 2 liter glass flask.

2. Add 900 ml of methanol. Stir with a plastic stick. A colorless solution will be obtained.

3. Place the solution in a clean container and close tightly.

It is very important to place tags with the name of the solution, composition and time of its manufacture on containers with ready-made solutions in order to avoid errors in application!

METHODS OF USE.

methanol solutions.

General information.

It is important to remember that CA does not reveal hidden traces that are not stained with blood. Use HA only when blood is visible and standard trace detection methods do not discolor the blood. Careful use of powders and ninhydrin does not preclude further use of HA. However, the use of cyanoacrylates largely minimizes the potential for NA. Physical methods and powders can be used after the application of HA. IMPORTANT: All bodily fluids such as semen, saliva, urine and blood for testing must be collected prior to using HA. Anyway, all visible objects are photographed before using the NA.

IMMERSION METHOD.

1. Blood protein fixation - If during the inspection of the scene it is possible to save or fix blood on the subject of research, then the method of immersion in a methanol solution is used. Place each object in a closed container for approximately one hour. Remove the methanol when they are colored. IMPORTANT: Some items may be subject to some changes. Used methanol must be destroyed. If the fixation with methanol is insufficient, then exposure of the object to the carrier of the heat source accelerates the reaction and enhances the intensity of staining. In this case, a lamp or similar heat source is used to heat the desired area of ​​the test object for up to 1 hour immediately prior to application of the NA.

2. Detection of blood proteins. – Prepare three containers of sufficient volume to contain the test object. Place a sufficient volume of working solution into the first container. In the second - the corresponding volume of the first rinse solution, and in the third - an acetic acid solution of distilled water for the final rinse. Place each item in the working solution until the marks turn dark. This will take two to three minutes. Add solution if needed. Strongly colored working solution for storage and subsequent use is not subject.

3. Cleaning the background. – Immerse items in the primary flush solution. Shake the solution gently to remove excess dye from the background. Change the wash solution, if necessary, depending on the intensity of the stain. Collect used solution after each flush.

4. Final flush. – Place objects in an acetic acid solution of distilled water for rinsing. Shake the solution bottle gently to remove any residue. Change the solution, if necessary, depending on the intensity of the stain. Collect solution after each wash and discard.

Forensic - used in the field of technical and forensic scientific research: photographic, traceological, odorological, ballistic, etc. - structural and forensic - methods for building certain structural systems in forensics (for example, a criminal investigation plan, tactics, methodological recommendations) By source origin...

Programs or devices, i.e. is directed to other information or devices for its operation, then it should be attributed to material evidence. In the process of practical work on collecting evidence in the investigation of crimes in the field of high information technology, electronic information should not be distinguished into physical evidence and documents for any one of ...