Guidelines for investigators on the detection, seizure, packaging and preparation of physical evidence for examination in the departments of the bureau of forensic medical examination. Questions to be answered by an expert. Procedure for examining material evidence.
Important in solving crimes is the ability to identify material evidence with traces of biological origin, read them and give them a correct assessment during the investigative examination of the scene of the incident or the place where the corpse was found, to orient to which department of the laboratory of the forensic medical examination bureau it should be sent earlier for confirmation or obtaining new information about the deed, which will allow solving the crime in hot pursuit. However, complete information can only be obtained when the investigator:
– skillfully and correctly fix the detected traces on the objects-carriers;
– withdraw them;
– carefully and correctly prepare for laboratory tests;
– make a list of issues to be resolved by an expert;
– will be determined in the order of the study of the carrier object (and not the carrier item, since the distinction between the means of causing damage to objects, tools and weapons is within the competence of a forensic expert, therefore forensic experts call objects, tools and weapons instruments of injury) ;
– evaluate the results of the expert study, comparing them with the information available by the time the expert’s opinion was received.
Detection of objects with traces of biological origin
The detection of objects with traces of biological origin at the scene of the incident allows during the inspection to put forward certain investigative versions, and in an hour to reveal what happened in hot pursuit.
When examining the scene of the incident, the investigator and specialist must proceed from the rule: “Each action of the person causing damage leaves a trace.” Finding an object to be researched is sometimes difficult. This is due to the lack of knowledge of the investigator, based on the damage on the victim or suspect, where on the carrier object and using what methods and devices to look for a trace.
The search for poorly distinguishable traces on the instrument of injury is carried out in oblique incident light, in ultraviolet and infrared rays, using appropriate instruments. When searching for traces, a specialist should be guided by the following rule: “Do not leave your traces, do not change, do not damage, do not destroy the trace on the carrier object.” The search for traces is carried out in medical gloves. If there are none, then a solid object is taken by narrow edges, edges and ends.
When removing a host object with unprotected hands, you should not:
– take edges for flat wide surfaces, as the authors of forensic textbooks write, because face is a plane;
– cover the narrow parts of the instrument of injury, pinching them with the fingers of the hand;
– introduce any objects into the bore of the firearm to manipulate it;
– take a projectile and cigarette butts for medical and forensic research with tweezers without protective tips;
– take objects-carriers for cytological and immunological studies with tweezers without protective tips and hands not protected by rubber gloves.
Such actions contribute to the appearance of additional traces not related to what happened.
To search for traces of sperm and blood, ultraviolet rays are used using a mercury-quartz lamp. The search is carried out in a darkened room. In the rays of a mercury-quartz lamp, the trail of sperm has a grayish-bluish glow, and blood is dark brown and velvety in appearance. If changes have occurred with the trace (environmental influences, stain removal, etc.), then such stains may acquire an orange-red color. In the rays of a mercury-quartz lamp, a number of substances, except for blood, can give a dark brown color and a velvety appearance, such as rust.
At the scene of the incident, specialists help the investigator to correctly detect, examine and describe the trace, remove and pack it, draw up a list of issues to be resolved on the trace, and determine the procedure for examining the carrier object in expert institutions.
The first of the specialists to examine the instrument of injury at the scene of the incident should be a forensic expert to identify fingerprints, then a forensic expert to detect traces of biological origin. Having found a trace on the carrier object, the specialist informs the investigator by commenting on the features of the trace, and then the investigator himself examines the trace correctly, taking the carrier object.
In cases of need, the trace is pre-processed for the purpose of fixation and preservation.
Instrument of injury
A glass, a bottle and other containers are examined by pinching the fingers between the ribs of the bottom and neck.
The knife is inspected, holding the blade and the butt of the blade between the fingers of the hand, or between the tip of the blade and the end part of the handle, if it is narrow and no traces are displayed on it.
The ax is taken by the end parts of the ax handle, and the hammer is taken by the handle.
Tools and weapons with corrugated surfaces are taken for corrugation. Firearms must first be taken, unloaded and fired by a forensic expert. Remove fingerprints on the weapon for fingerprinting. After that, the weapon is examined by a forensic expert to identify traces of blood and epidermis.
Traces on the instruments of injury
In the process of a fight with inflicting damage with blunt hard (cylindrical sticks, pipes, tools with a rib, with several ribs, flat with a limited and widespread surface), crumbling (red brick, clods of dried soil), crushing (bottle or jar glass) tools, injuries remain traces of biological origin on them, objects of the environment, the victim and the suspect.
Hits on the head with the above-mentioned instruments of injury, as a rule, inflict wounds in shape, and sometimes in size, which are judged by the characteristics of the instrument that caused the damage.
A blow with an injury tool with a straight rib causes a slit-like wound, with two ribs converging at one point an angle-shaped wound, with three ribs converging at one point – a three-beam wound, with an arcuate rib – an arcuate wound. A blow with the plane of the injury tool with a limited square, rectangular, round and other surface, depending on the angle and speed of impact, the wound fully or partially reflects the shape and size of the injury tool. A blow with an injury tool with a spherical surface leaves a multi-beam wound with a crush area and tissue loss at the point of convergence of the rays. A blow with an instrument of injury with a cylindrical surface up to 2 cm in diameter inflicts one slit-like wound, and more than 2 cm – two parallel slit-like wounds. Impact with an instrument of injury with a widespread surface – branching, tree-like, X- or Y-shaped wounds. A blow with an instrument of injury with a widespread surface in the area of anatomical formations in the configuration approaching a cylinder or sphere causes a star-shaped or x-shaped wound without loss of tissue at the point of convergence of the rays. A blow with an instrument of injury with a surface that collapses as a result of the impact inflicts several wounds of superficial wounds surrounding one deeper one.
Single blows with wooden, rusty metal, brick and glass instruments of injury, forming wounds on the head at the point of contact, leave overlays of wood fibers, rust, brick particles, glass fragments, respectively, detected when examining the corpse and his clothes at the scene. Blows on the areas of the body with the listed blunt solid instruments of injury do not inflict wounds in the non-projection of the bone, but the corresponding overlays remain on the clothes in the projection of the damage.
Multiple blows with wooden, rusty metal, brick and glass instruments of trauma, forming wounds on the head, at the point of contact leave overlays not only of wood fibers, rust, brick particles, glass fragments, but also form multiple blood splashes from waving and hitting the bloody surface.
These traces are revealed when examining the corpse, its clothes and the attacker, the instrument of injury at the scene of the incident, as well as when examining material evidence outside the scene and the absence of the corpse on it.
The injuries destroyed as a result of the impact of the weapon are collected and packed for further research.
From blows to the head, traces of blood are located on the front front surface and rarely on the wrong side of the attacker’s clothing, at the lower end of the sleeves or cuffs.
Damage caused by sharp (cutting, piercing, stabbing, chopping, sawing) instruments of injury, scissors, metal and glass instruments of injury with sharp ends, blades and ribs leaves wounds and damage to bones.
According to their features and sizes, they are judged on the design features of the trauma weapon, the method of application and the traces left by them.
According to the shape of the wounds, they tentatively express an opinion about the used instrument of injury:
– the rounded shape of the wound gives reason to believe about a stabbing injury tool that has a cone-shaped rod (awl, etc.), a four-beam one – a Russian bayonet, a rectangular one with breaks in the corners – a screwdriver;
– slit-like with acute-angled, one acute-angled another or, or U-shaped, or M-shaped ends allows you to judge the blade with one-sided sharp sharpening of the blade;
– slit-shaped, with acute-angled ends, indicates a blade with a double-edged sharpening, three-beam – a scraper (a file – sharpened on three sides), arcuate – a blade curved along the plane to the side, 8-shaped – a blade with a propeller-shaped bend, slit-shaped with settling in a circle – on a blade with a broken fighting end;
– the shape of an isosceles triangle, a spindle, a rectangle with breaks in the corners indicates a chopping instrument of injury.
On the bones, piercing-cutting, chopping and sawing tools leave traces that allow, in the presence of an injury tool, to identify it.
Human tissues almost always remain on the saws. In places of cuts, bone filings are found.
On all sharp tools, depending on the individual characteristics of the hairline of the human body, there may be hair fixed with dried blood.
Damage from a shot from a firearm into a leaky or edge stop leaves an imprint of the muzzle, which is used to judge the make and model of a firearm, and traces of blood on it and in it about the distance of the shot.
The action of the loop leaves a trace – a strangulation furrow, according to the features of which they judge the instrument of injury. When strangulated by professionals using a Jiggly saw or a string, the strangulation groove may be absent at the site of their action, but in its place there will be a wound similar to a cut.
Traces of blood on the instruments of injury are not always visible during examination, but are always found in cracks, depressions, attachment points of parts from which it is difficult to remove them. It is FORBIDDEN to disassemble the instruments of injury to search for these traces .
During the inspection of the scene of the incident, traces of blood are most often found on carrier objects, less often – fingers, saliva on cigarette butts, hair, and vomit.
When examining the victim, traces of blood are detected on headgear, clothing, shoes and body.
On clothes , traces of blood are located both on the front and back surfaces.
On headdresses , hidden traces of blood are localized on the inner band, the lining of the cap
On shoulder clothes – in bags of pockets, on the inner surface of the sleeves, on the cuffs of shirts under a jacket, on belt clothes – in bags of pockets, fly fasteners, and in cases of sexual crimes on underwear, on the wrong side of the bottom of the legs.
On shoes – on soles (soles), heels, in depressions, cracks, junctions of shoe parts
On the suspect, traces of blood can be found in open areas of the body, on the face, neck, forearms, hands, in the interdigital folds, nail beds, under the nails, on the scalp, and in cases of sexual crimes – on the genitals and pubic hair.
Detection of traces of blood in the room starts from the entrance and continues the inspection, clockwise inspecting the door, walls, furniture standing against the wall, household items, clothes on furniture, and shoes standing under it, and then describe the ceiling, floor , objects and furniture, spaced at some distance from the walls.
During the inspection of furniture , attention is paid to the joints of furniture parts, cracks in it, the handle, the bottom surface of furniture drawers, and legs. It is convenient to inspect the lower surface of furniture, as well as doors, using a mirror. If there is none, then the door is removed from the hinges, and the furniture is turned upside down. Examining the mirrors, pay attention to their back surfaces, where sometimes they find bloody fingerprints with well-defined papillary patterns.
Inspection of bathrooms reveal traces of blood on taps, low tides, soap dishes, towels, rags, washstands, drains.
On vehicles, traces of blood are found on the outer surfaces of vehicle parts – bumpers, headlights, sidelights, radiator, front cladding, hood, windshield, on the sides, lower surface of transport parts – wings, front beam, bottom of the body, passenger vehicles – suspensions, in the cabin and cab – on the windshield, steering wheel and column, interior lining, doors, rugs, seats. On wheels, traces of blood can be located both on the outer and inner surfaces of the wheels, as well as on the treadmill, at the junctions of various parts under the lower surface of the transport, indentations and destruction caused by the impact of the victim’s body.
To reveal hidden traces of blood on upholstered furniture and clothes , they undermine and carefully inspect the seams, layers of gaskets and lining, layers of cotton wool, turn pockets and clothes inside out, separate the sole (soles), heel, remove the top layer of shoe polish with a cotton swab.
Blood in the room is usually removed with rags, buckets and other containers with water are used, in which blood may remain. Therefore, conducting a targeted search; pay close attention to the listed items, on – and in the contents of which there may be traces of blood.
If blood is suspected, carefully examine the cracks of the floor, parquet, their junctions with baseboards, fillets, platbands, and ventilation grilles. In cases where there are no traces of blood on the listed details, the floor and parquet are torn off, and then the space between them and the floor base is examined.
If, after committing a crime, the offender washed his bloodied hands, then traces of blood remain on the tap or other container, and in the contents of the garbage can, the siphon is water stained with blood. To identify them, it is necessary to disassemble the siphon or drain, pour the contents of a garbage can or other container with bloody contents into a clean container with gauze at the bottom to soak it with blood.
Sometimes criminals deliberately destroy traces of blood , but along with this, blood always remains in those places where it is difficult to remove it – in the seams of clothes, pockets, recesses and crevices in the floor, siphons of sinks, toilet bowls, the lower surface of furniture, at the junction of parts of objects , tools, weapons, vehicles, which dictates the need for a thorough and systematic inspection of the scene using some research methods: inspection in ultraviolet (UVL) and infrared (IR) rays, photographing on photographic materials sensitive to infrared rays and using some techniques – examination in obliquely falling artificial lighting, careful scrapings of suspicious spots.
Under the influence of environmental factors, the blood changes its color. Green traces of blood and traces located on a dark, variegated or heavily soiled object are detected using an examination in UFL and ICL. Under the influence of ultraviolet rays or blue color, the blood, absorbing UV light, will turn brown. In cases of examination in the ICL, traces of blood have a darker color than the rest of the surface of the carrier object.
Preliminary samples recommended in textbooks and manuals for the presence of traces of blood at the scene with a diameter of not more than 0.5 cm destroy them. Therefore, it is forbidden to use them in the presence of extremely small amounts of blood. A positive preliminary sample at the scene, in the laboratory, using a reliable test method, will give a negative result, which will lead the investigation into the wrong path at the initial stage.
It is important for obtaining reliable results that the investigator correctly seizes and packs the identified material evidence.
Before removing a trace on a carrier object, it must be photographed and described. Traces of liquid substances and prints must be photographed in detail with a scale located at the lower edge (end) of the trace.
When proceeding with the seizure of material evidence, it is necessary to prepare containers and packaging material (boxes, boxes, bags, envelopes, sheets of clean white paper, etc.).
The removal of research objects of biological origin is carried out only with medical gloves, in order to avoid getting sweat-fat secretions of the fingers of the person who selects the research objects, since the admixture of foreign secretions can lead to incorrect conclusions. If there are none, then the solid object is manipulated as above.
The main rule that guides the seizure of objects is the seizure of all objects with traces of criminal acts in volumes suitable for research.
When seizing material evidence, one must adhere to the rule: Do not leave traces of your hands, do not damage or destroy the trace. Therefore, it is not worth rushing to remove the trace, especially for a young specialist and an investigator. Before removing the trace, it is necessary to mentally imagine the sequence of actions in order not to violate the above rule. The way physical evidence is removed and its packaging depends on the characteristics of the trace and the carrier object. Therefore, the techniques used vary depending on these conditions.
During the inspection of the scene of the incident, traces of liquid blood are most often found on carrier objects, less often – fingers, sperm, saliva on cigarette butts, hair, vomit and feces, which must be seized and sent to the appropriate department of the forensic medical examination bureau.
The removal of the trace is carried out with the carrier object, flushing, or scraping from it, removing part of the carrier object, impregnation with a liquid medium.
Removing a trace with a carrier object
It is preferable to remove a trace on non-bulky carrier objects with a carrier object. In this case, the morphological features of the trace are preserved and the trace does not change, which greatly facilitates the work of the expert. By the time the scene is examined, the traces of blood, as a rule, dry up and fix the hair and tissues to the instrument of injury. They, as well as overlays on small instruments of injury, clothes, underwear, cigarette butts, condoms are confiscated together with the carrier object – instruments of injury, clothing, and not bulky furnishings.
Instruments of trauma
The injuries destroyed as a result of the impact of the weapon are collected and packed for further research. Brick, asphalt pavement, cobblestone, paving slabs and their parts, glass fragments and broken dishes with the largest amount of blood and traces similar to it located in one place are seized and placed in one box or box of the appropriate size. If they are at different distances, then they seize each object with traces of biological origin and pack it in a separate box (box), indicating the location. Small particles of brick and glass fragments, soil, dried leaves, etc. are placed in paper envelopes.
Wood fibers are removed on adhesive tape or dactyl film.
Bone fragments are collected and packed in clean jars, and sawdust – in test tubes.
Wearables , small items and instruments of injury are packed in cardboard boxes in which they are fixed in cutouts of cardboard jumpers.
The shot is collected and packed in one bag.
Bullet and wads , if they are not saturated with blood, are packed in a bag. Wads soaked in blood must be packed in a matchbox or in a pack of cigarettes. Wads from a sheet of paper soaked in wet blood are straightened and placed in boxes with at least three jumpers that prevent deformation.
The noose on the corpse at the scene, as a rule, is not removed. In extremely necessary cases, it should be cut in a place opposite to the localization of the node. If there is a strangulation groove and there is no loop (s) from its location, as well as from the hands of the victim, it is necessary to remove the overlays with adhesive tape. The same manipulations should be carried out immediately after the arrest and with the hands of the suspect.
Large items and bulky items with dried blood are packed in wrapping paper.
From bulky objects of no value , the trace is cut out, sawn out, planed, peeled off, beaten off and sent with a part of the same carrier object, where the trace is absent, for a control study.
Vomit and feces, washing water are removed into clean, dry glassware.
By the time the scene was examined, blood, semen, etc. they dry up and are removed along with the instruments of injury, clothing, and not bulky furnishings.
Traces of blood on the soil are dug in and cut from below with a shovel, so that a piece of soil remains intact, which is carefully wrapped in clean paper and placed in an appropriately sized box or box. For research, no more than 200 g of soil with the most blood-soaked areas is selected. Prior to the study, the investigator, in the presence of worms and insects, removes them from the soil. The taken soil is poured in a thin layer on a plate and dried at a temperature of +37°C. The same is true for control samples.
Traces similar to blood in the liquid are removed into a clean penicillin vial with a capacity of at least 10 ml and stored in a refrigerator (not in a freezer) until it is presented to the experts. If it is difficult to do this, the liquid is soaked with several pieces of gauze bandage measuring 10×10 cm. For control, a piece of gauze bandage measuring 10×10 cm is left.
By the time the scene of the incident is examined, the traces of blood dry up and fix the hair and tissues to the instrument of injury , clothing, and not bulky furnishings. In such cases, carrier objects with traces of blood, hair and overlays are removed along with them.
It is IMPOSSIBLE to pack items with both dried and liquid blood in plastic bags , because. the air remaining in the bag cools and heats up, forming moisture droplets that contribute to rotting.
Separate hair or fibers similar to hair , on the instruments of injury, the clothes of the suspects and the victim, in the hands of the victim, toilet items (combs, massage brushes, curlers, etc.) are removed with tweezers, packed in a sheet of clean thick paper, sealed, accompanied by an explanatory inscription on the label. You can not fix the hair with adhesive tape, as this can lead to mechanical damage.
For a comparative study, the hair of the victim and the suspect is removed. If there are several suspects (more often in cases of sexual crimes), then hair samples of all persons must be provided. Hair is cut with scissors at the root of the hair (strands of 20-30 hairs) from five areas of the head: frontal, parietal, occipital, temporal, and in addition, from the beard and mustache, if any, of the pubis. The seized hair is packed in signed paper bags like “pharmaceutical powder”, put in a separate pre-signed envelope (you can use a standard postal or home-made one), sealed.
Nails with subungual contents are seized by the investigator from the suspected of committing a crime, experts from the department of victims, defendants and other persons, experts from the thanatological department. Seizure is carried out immediately after detention. Before removal, both the investigator and the experts should photograph the nails of the right and left hands on a scale for subsequent identification studies conducted by the experts of the abrasion medical forensics department. Under the cut nails, separately from the right and left hands, a clean sheet of paper is placed. It is necessary to cut the nails so as not to damage the skin of the fingers and the cut nails do not “fly away”. To do this, the index finger of the hand manipulating the scissors is placed in the projection of the nail cut with the cutter of the scissors. Cut off nails, from each hand, are packed in pre-signed paper bags folded like “pharmacy powder”, put in a separate pre-signed envelope (can be in a standard postal or home-made), sealed.
Cigarette butts , rarely used chewing gum, condoms are removed with gloves or with rubber-tipped tweezers.
If there are many cigarette butts at the scene of the incident, the investigator seizes no more than 10 cigarette butts of the same type. Sorting them by manufacturer (if there is an inscription on the cigarette sleeve), filter color (yellow, white, brown or other color), according to the method of extinguishing “characteristically crumpled”, the presence of any distinguishing features (for example, the presence of overlays or spots, in appearance resembling lipstick, blood, etc.). Dry cigarette butts with obvious traces of smoking are subject to selection.
After sorting the cigarette butts, 1-2 cigarette butts are selected from each group, packed in matchboxes or cigarette packs, sealed and, with the appropriate inscription, sent for examination to an expert of the forensic criminology department or the forensic cytology department.
In the presence of suspects and victims, it is necessary to provide samples of their blood and saliva for forensic cytological examination. Blood is provided in a disposable syringe of at least 2 ml, saliva on a sterile piece of gauze bandage folded into four layers of 5×5 cm. In the conditions of regional centers, sampling is carried out in the Central District Hospital. Samples must be submitted to the laboratory on the day of collection. If it is not possible to provide samples on the same day, they must be stored in a refrigerator (not in a freezer), delivered the next day to avoid putrefactive processes. When selecting saliva on gauze, it is necessary to avoid “sucking” traces of blood on it. The best option for taking blood and saliva samples is to take them in a laboratory. If samples are delivered by the investigator, they must be packaged, sealed and signed in clear and legible text.
Overlays of cells of biological origin on the instruments of injury, transport, firearms, at the scene and clothing of the suspect, especially dried ones, can remain for a considerable time and, under favorable conditions, do not change. Such overlays, depending on the dimensional characteristics of the instrument of injury, are removed either together with them, or by scraping into a clean test tube (if the overlay is already dry). Wet traces are best placed on thick, clean paper. If possible, a sample of the carrier item should also be provided. Under no circumstances should overlays be transferred to adhesive tape.
Condoms , both with traces of liquid semen and dried ones, are withdrawn into a cardboard box above the length of the condom. A U-shaped spacer is inserted into the box with a hole at the top slightly smaller than the diameter of the condom. A condom is lowered into this hole, which is straightened in the hole. In this position, the sperm in the condom dries up, reducing the possibility of development of putrefactive processes.
Chewing gum is packed in a matchbox with strips of clean white paper laid crosswise on the bottom, which covers the carrier object.
When a corpse is found with advanced putrefactive changes or partially skeletonized, especially in the warm season, it is necessary to remove eggs, larvae (maggots), mature individuals and puparia (pupa) of flies for forensic entomological examination according to the method proposed by A.A. Prokopenko head. laboratory of forensic, chemical and biological research, KhNIISE them. honored prof. N.S. Bokarius, Ph.D. biological sciences.
For forensic entomological studies, it is necessary – When a corpse is found in an open area:
– collect adult insects with a net (flying forms) or tweezers (crawling forms).
The collected insects are fixed in glass containers (70 degrees, alcohol or 4% formalin solution are used as fixing liquids). The maximum possible number of species is collected, based on their external features (color, size, shape)
– collect larval forms and oviposition. The maximum possible number of species is collected, based on the signs of their external structure. Fly larvae must be collected (40-60 specimens) from different parts of the body, since different species, as a rule, form clusters delimited from each other. Part of the collected material is fixed in glass containers using 70 deg. alcohol; part of the material is left in its natural form in glass containers, on the bottom of which is placed a layer of moistened sand (3-5 cm) and part of the food substrate on which these larvae are found.
– insect pupae and only hatched insects (especially Flies) are collected separately,
which differ from adult insects in low mobility and light integuments of the body. These objects are placed in glass containers without fixing liquids.
– since most necrobiont forms complete their development in the soil, it is necessary to take 5-6 soil samples (to a depth of up to 20 cm) from the corpse bed and within a radius of 1-2 m from the corpse. These soil samples are placed in plastic bags.
When a corpse is found indoors, collect a variety of entomofauna, as well as in open areas, especially from cracks in the floor, near lying objects, clothes, because. indoors, the larvae are unable to pupate in the soil.
All collected material (each container) is provided with a label indicating the date, time, place of detection of insects (for soil samples, the place of sampling is indicated).
All collected material is delivered as quickly as possible (preferably within 24 hours) to the laboratory for research
When a corpse is found in a reservoir, water is taken to compare the elements of plankton found in the tissues of the corpse with the elements of plankton characteristic of this reservoir.
Before taking a water sample, it is necessary to rinse the liter jar twice with water from the given reservoir in which the corpse was found. The fence is carried out from the surface layer at a depth of 10-15 cm at the site of the discovery of the corpse. The dishes are closed and sealed by the investigator. The label indicates the date, time and place of taking, the name of the investigator who took the water.
Algae and fungi that have settled on the corpse must be removed and sent for forensic botanical research to determine the period of stay; corpse in the water of this reservoir
In the presence of human parasites, they are removed and sent for biological research in order to establish the limitation of the corpse’s stay in the water.
If the carrier object cannot be removed, then an object with traces of biological origin, subject to expert examination, is removed from it by washing or scraping.
Blood splatters on items of complex household appliances, works of art, bulky furniture are removed depending on the amount either with a damp cotton thread or gauze, leaving samples that are sent to the laboratory along with carrier objects.
Traces of blood or blood-like spots on the human body are removed with a piece of gauze bandage soaked in distilled water or physiological saline solution. The size of a piece of gauze should be approximately equal to the size of the stain, but not less than 2×2 cm. For very small traces of blood, a thread 1.5–2 cm long is taken from the gauze. The trace is carefully rubbed with different sides of the piece of gauze, trying to remove all blood from it.
The traces removed by the flush are dried, properly prepared for laboratory research and sent to the laboratory.
Scraping removes a trace from large low-value and difficult-to-remove parts or parts of wooden, glass and metal objects with a non-absorbent surface. For example, the concrete surface of the wall. First, dry ones are removed with a sharp scalpel or a thin knife; particles and crusts, which are placed in a paper bag, then the scalpel is placed at an acute angle and the rest of the mark is scraped off so that the clean plaster does not mix with it. For control, next to the trace of blood, a part of the plaster is scraped onto the paper. In order not to lose the object removed from the vertical surface, a clean sheet of paper is placed under it and the object is scraped off with a sharp scalpel or safety razor blade in the direction from the bottom up, which is packed in a paper bag like “pharmacy powder” or from the sheet, the scraping is poured into test tube. For control, a part of the object is taken outside the trace location zone. If there are several objects-carriers, a scraping is made from each of them on a separate sheet of clean paper and each scraping is packaged separately (as indicated above), indicating on the package from which particular spot mentioned in the inspection report this scraping was obtained. This requirement is due to the fact that similar-looking spots, located even on the same surface, can have a different origin.