Go Special types and methods of forensic medical examinations for mechanical damage | Forensic Medicine
Go

Special types and methods of forensic medical examinations for mechanical damage

  • Body damage
  • Multiple damage
  • Physical and technical research methods
  • When analyzing damages and various traces of external influence, it is extremely important to establish the nature of their origin, which is associated with the identification of the damaging tool.

    Objects on which the prints of other objects remain, in forensic science, are designated as traceable, and those objects that are displayed on them are traced.

    The branch of forensic science, which studies the traces of how the external structure of objects is displayed for the purpose of their identification or the establishment of their group affiliation, is called trasology .

    The features of the external structure of damaging objects during mechanical impact are displayed in the form of various kinds of traces: impression marks (for example, a depressed skull fracture when struck with a hammer, an imprint of a car wheel, a striker striker face on a capsule of a sleeve, etc.) bone cutting with an ax, dragging, etc.).

    Damage to clothing from the effects of traumatic objects can be quite diverse, depending on the nature of the object and the mechanisms of external influence. Identifications are subject to parts of damaging objects, traces of the impact of which in varying degrees, found a display on clothing or body.

    Go

    Dull solid objects with a fairly wide surface with a direct impact on clothing and body form a trace - the area defined by the contact boundary. At the same time, overlay (for example, soil contamination during a fall) may remain on clothing and body. The impact of a blunt object, which has a clearly defined edge or border, leaves on the clothes a compaction of the fibers according to its contour, and with a sufficiently sharp edge even the severed fabrics of the clothes.

    A striking object that has impurities on its surface (soil, technical lubricant) leaves a clearer contour on clothes. Corresponding to this contour on the body, the formation of bruises or wounds is possible (strikes with a wrench, etc.). When exposed to a very significant force, it is possible to spread clothing fabric (for example, moving by rail wheel). In the process of impact interaction, particles of fibers of damaged clothing fabric (application) remain on the injuring weapon. When the body is traumatized in places not covered by clothes, the epidermis scales, hair, and blood can be found as overlays on the damaging instrument.

    Traces of blunt solid objects in some cases can be detected quite easily (for example, an imprint of a car wheel tread), in other cases it is difficult to establish them and requires special laboratory tests (for example, detection of metallization at the impact point).


    Fig. 74. Traces of slip on the sole.

    The tangential effect of blunt objects often causes, in addition to contamination of clothing (for example, when dragging), its damage in the form of tears. When struck by a part of a pedestrian car, the latter often receives a rotational movement around the longitudinal axis of the body before falling. In such cases, on the sole of the shoe there are characteristic traces of slip (Fig. 74).

    Go

    When moving through the body of a person, the wheels of a vehicle may experience overlapping treads and signs of damage. It should be noted that both those and others quite often do not fully reflect the contour of the damaging object (wheel) and, at best, allow us to judge the model of the tire (but not the car).

    Damage of clothes in the form of smoothing out of a kind of folds, gaps parallel to the seams, tearing of buttons during tension of clothes due to rolling of a car wheel (fig. 75) are quite characteristic.


    Fig. 75. “Smoothing” of clothes folds with a car wheel when moving (the arrow indicates the direction of wheel movement).


    Fig. 76. Imprint of the tread on clothing and its rupture due to collision

    The breaks of clothes from tension are usually oriented transversely with respect to the direction of external influence (Fig. 76).

    Breaks are always linear or rectangular, coincide with the direction of the warp or weft. The mechanism of their formation consists in stretching the threads of fabrics with the subsequent rupture, in connection with which the broken threads have spindle-shaped, fibrous ends.

    Under the action of the cutting object, the threads along the edges of the defect are even, and the incision itself, as a rule, does not coincide with the longitudinal or transverse direction of the threads, but to some extent intersects them at a certain angle. Sliced ​​damage to clothing may not be linear, but zigzag-shaped in those cases when the blade of the damaging tool cuts several layers of clothing gathered into folds. A non-sharp cutting tool, in addition to an incision, can also cause tears.

    When exposed to a chopping object, damage to clothing is often continued as an indentation from a blade that comes into contact with clothing. With a strong blow with an ax and a deep immersion of the blade, the ends of damage on clothes take a U-shape, especially in cases of preferential immersion of the “heel” or “toe” of the ax blade.

    Damage to clothing caused by piercing objects depends on the shape of the blade and its cross-section. An object having a blade and a pickaxe forms a damage that resembles an exclamation mark, while a double-blade weapon (double-edged) causes damage that resembles a cut. Stab-cut damage on clothing in length can significantly exceed the wound in those cases when, when removing a damaging object from the wound, the angle changes and an additional incision occurs due to the action of the tip of the blade or the butt edge.

    Stabbed damage to clothing occurs as a result of the fabric being pulled apart and the tearing of individual threads or their overstretching. Such a mechanism of damage contributes to the fact that a wiping belt is formed along the edge of damage due to friction, laboratory tests of which allow to establish the character of the metal of the damaging tool and, in some cases, to differentiate piercing and firearms. In addition, studies of overlays (lubrication, contamination) from the wiping belt area can provide important information.

    It has been established that, when immersed at a speed of up to 3 m / s, the pointed conical round section forms a folded radial relief around the hole with the deposition of the metal of the damaging tool on the top of the folds of clothing. Immersion with greater speed usually does not give such an effect (Fig. 77).


    Fig. 77. Stab damage clothing. The nature of the metal deposits around the damage to clothing. a - at a sink rate of 3 m / s; b - 0.5 m / s; in - at an acute angle.

    With gunshot injuries on clothes, most of the components accompanying the shot are deposited, while on the body they may be completely absent. It should be borne in mind that on the tissues of different color and quality, these components are detected unequally and, in addition to an external examination of the area of ​​damage, it is necessary to use laboratory methods and research.

    Damage to clothing should be carefully examined and the thickness of the clothing layers should be measured, which, together with the determination of the depth of the wound channel, allows judging the length of the wounding blade.

    In the process of producing an external examination of a corpse when using it in the morgue, a very important part is the use of direct microscopy. With the help of an operating microscope (a stereoscopic microscope MBS-1, a luminescent photodiagnoscope, etc.), the properties of damage on clothing, contamination and impositions are detected. Particular importance should be given to the use of this method in the study of lesions on the body.