“Evidence recognized any items which served as instruments of crime or have retained on themselves the traces of the crime, which was directed the criminal acts, property, money and other valuables obtained through criminal actions or acquired by criminal means, other objects and documents that can serve as a means for the detection of crime and establishing circumstances of criminal case”. (article 81 of the CPC.
To find out the attitude of the seized item to the crime and the evidentiary value of this object in many cases is possible only by examinations.
Depending on the nature of the evidence and the issues to be addressed, expertise can be different.
Objects of forensic medical examination of material evidences are very diverse: blood, bodily excretions, hair, bones, soft body tissue, etc.
To the production of these examinations is allowed only doctors – forensic experts who have undergone special training in forensic examination of physical evidence.
In the research process, physical evidence, the expert is required to economize subject to the object so that part of it was left for a possible re-examination. If the total consumption of the object it was impossible to resolve the issues before the examination, it is stipulated in the relevant document (policy – accompanying document to the expert report.
All the data on performed studies and the results of their expert daily contributes to the work journal, source document, based on which the relevant resolution is issued. When the forensic this conclusion is given the form of the act, including: the introductory part highlighting the summaries of the circumstances of the case, the sections “Description of physical evidence and samples submitted for comparison, a Study” with appropriate subsections and a Conclusion. The original copy of the deed is sent to the destination, the duplicate remains in Bureau is judicial-medical examination. However, the act returns the physical evidence and samples for comparison, subjected to the examination.
Traces of blood on physical evidence are of great importance for the investigation of crimes, such as murder, rape, theft.
They can be formed on different objects in the scene, the clothing and body of the criminal and the victim, murder weapon, etc.
Detection of traces, suspicious on a bleeding.
The discovery of traces of blood sometimes difficult due to the color change of blood under the influence of time (the time that has passed since the occurrence of traces) and various environmental influences, on the one hand, and intentional acts aimed at the destruction of traces or accidental violation.
Red or dark red of fresh blood becomes red-brown, brown, brown, sometimes black, and even gray-green. Sunken and washed away the traces may be pinkish-yellow or yellowish color.
Background, on which there are traces, often making them difficult to identify: on a dark, colorful and contaminated items blood difficult to see; the same applies to objects, the colour of which in one way or another similar to the color of blood.
Attempts by the perpetrator to destroy the blood traces dictate the need to search for them in places where blood is difficult to remove: in the seams, the pockets, the strips of material between the uppers and lining of clothing, in crevices of walls, fences, depressions in the floor, etc.
For the detection of traces, suspicious on the blood, above all we recommend that you thoroughly inspect the items to the naked eye. While great importance is the lighting. Very clearly the traces of blood are when viewed in sunlight or bright artificial lighting. In cases where traces of color merged with the color of the background on which they were formed, good for weak artificial side lighting. The rays of light directed at the subject under more or less acute angle, allow you to see areas that differ from the rest of the surface (smoother or more rough spots.
Inspection with the naked eye complemented by the use of available technical means. The identification of traces of small size facilitates viewing objects with a magnifying glass. Slight traces of blood, in particular washed away, become visible when viewed in ultraviolet rays; however, they become brown. However, the effectiveness of this technique largely decreases the adverse observation of the original or changed as a result of the luminescence color of the object, i.e. the object on which blood traces. In addition, when examined in ultraviolet rays brown marks not only blood, but other substances, such as rust.
Good results are obtained by photographing physical evidence in the infrared; black and white photographs traces of blood at sufficient density of the layer stand out against the background darker or, conversely, a light color.
The use of certain chemicals for the detection of blood is permissible only when the identification of traces associated with particular challenges. In ordinary cases, the application of these reactions cannot be considered appropriate, as this may cause damage to the blood. Experiments established, for example, reaction with hydrogen peroxide and luminol complicate the further definition of the blood group – weaken isoserological agglutinins of ABO system in that part of the track, which has undergone the action of appropriate reagents. In addition, you need to keep in mind that the proposed chemical reactions are only indicative, i.e., a positive result does not prove the presence of blood, and a negative does not exclude its presence.
The most common reactions are: with hydrogen peroxide, benzidine, luminol.
One or two drops of three percent hydrogen peroxide solution applied with a glass rod or Pasteur pipette on one of the edges of the suspicious track. A positive result is expressed in the formation of foam due to oxygen release during the decomposition of hydrogen peroxide with enzyme of blood. However, such enzymes are not only in blood but also in many other substances, which makes the reaction specific for blood. In addition, the response and non-permanent: can be negative with the blood. It depends on the loss of enzyme activity.
For benzidine reaction using the reagent, produced by V. I. Voskoboynikov recipe: 2 parts the primary benzidine, 10 parts of citric acid, 5 parts of peroxide of barium. The ingredients are ground in a mortar to a powder. Before applying a small amount of powder was dissolved in water (2-5% solution) obtained by the liquid moisten a swab of cotton wool and touch it to the edge of a suspicious blood trail. The appearance of blue staining of the tampon is evidence of the oxidation of benzidine from the decomposition of barium peroxide by the enzymes contained, particularly in the blood.
Reaction with luminol (3-aminophthalhydrazide) based on chemiluminescence – illumination arising from the oxidation of luminol and peroxide decay of its compounds. Many substances, particularly blood and red blood salt (potassium genesisintermedia) are the activators, i.e., increase the luminescence. The reaction proceeds in an alkaline environment. 0.1 g of luminol and 5.0 g sodium bicarbonate (baking soda) dissolved in 1000 ml of distilled water. The resulting solution may be stored in a flask made of dark glass 6 – 8 months. Before use, add perhydrol is based of 10.0 g per 1000 ml of solution. In a darkened room a drop of reagent is applied to the edge of the suspicious trace or, for example, when inspecting dark basements, cellars and spray them (spray dispersion) in the study subjects. A positive result is the outbreak of a luminescence of blue color, lasting 60 – 65 sec.
Benzidine reaction and the reaction with luminol, too, are indicative and do not prove the presence of blood. A positive result indicates binding of further laboratory studies to proof the blood of their origin. A negative outcome indicative of chemical reactions does not preclude the need later study.
Description of physical evidence.
With the finding of traces, suspicious on a bleeding, in the inspection Protocol thoroughly describe the evidence and its traces and photographing them, rationally combining both techniques (it is desirable to use a color photo.
The characteristics of the evidence include: 1) the exact name of the item; 2) material name (wood, marble, plaster, cotton, silk, etc); 3) form; 4) style (clothes, shoes); 5) color; 6) size or weight (e.g. loose body); 7) the degree of deterioration; 8) pollution; 9) features.
Localization of tracks similar to blood, usually clearly recorded in photographs. If for some reason you have to do without photographing, describing note the location of the marks on a particular side (front side, reverse side, or outer and inner sides), the surface (front, back, top, bottom, left and right) and region (gender, collar, ax, blade, etc.) evidence.
The origin of the trace determines its character.
When draining large amounts of blood from injured parts of the body there are puddles of different shapes and sizes.