3D MODELING OF EXPERIMENTAL WOUND CANAL CAUSED BY STABCUTTING TOOL WITH ONE-SIDED SHARPENING OF THE BLADE

Abstract

The aim – to carry out 3D modelling of the wound canal formed by a stab-cuttingtool with one-sided sharpening of the blade, using photogrammetry method for furtherinvestigation of its morphological peculiarities and obtaining linear dimensions withhigh accuracy in the space of the graphic editor "3ds Max".Material and methods. Fifteen experimental wound canals were reconstructedby means of an alginate imprinting mass with a rubber-like effect "Hydrogum 5"(Zhermack, Italy), which hardens quickly, remains elastic after polymerization, allowsto obtain imprints with an extremely smooth surface andmost accurately preserves andreproduces the properties of the immersed in it blade of the knife under study. Astabcutting tool - a knife with one-sided sharpening of the blade, blade length - 9.6 cm,width in the place of the greatest blade thickening - 2.6 cm, butt thickness - 0.24 cmwas used to mark experimental damage. Given dimensions of the stab- cutting toolwere obtained by means of sliding caliper with an error of ± 0.03-0.15 cm. The formedwound canal was divided into fragments with a step of about 3.5 cm. Each fragmentof the wound canal was contrasted with dye (1% alcohol solution of diamond green).These fragments of the wound canal were opened parallel to its length and placed on arotating table, which was located in a light cube to provide sufficient illumination andphotography was performed. A SONY RX 10 II digital camera was used for taking aphotograph. The index number and a fragment of a scale ruler 1.0 cm long were placedon the object for further calibration of the scale and control of the dimensions of theobject under study in computer programs. The photos obtained in JPEG format wereloaded to the computer program "Agisoft Photoscan", where 3D textured models of thewound canal fragment were created. The obtained model and texture were exportedin OBJ format. Then the obtained 3D models were moved to the graphic space of theprogram "3ds max" to calibrate the scale of the model and in the graphic editor thereconstruction of the wound canal was carried by means of 3D models of its fragments.Results. Measurements of the linear dimentions of damages were carried out at firstby a classical method (by means of a ruler). In addition to, that the depth of the woundcanal, which consists of three fragments, was obtained according to the method ofmeasuring the depth of the wound canal in the body of the corpse by putting togetherits seperate parts in accordance with immersion and permeability of the blade in thevictim's body (skin, subcutaneous muscle tissue, cavity wall and in it itself, the internalorgan and other anatomical formations). Similarly, the width of the wound canal andthe distance between the corners from the side of the butt, which illustrate the thicknessof the blade of the cutting edge and the length of its separate fragments, which in itsturn reproduce the parameters of the blade of an acute traumatic object, were fixed at different levels of immersion.The next stage of our work was to study and obtain the linear dimensions of 3Dmodels’damage by means of a graphic editor "3ds max". In this case, the mentionedcomputer program allowed to obtain the dimensions, described by us,already by anorder with higher accuracy (up to 0.001 cm).The results, obtained by us in the experiment, allow to assert about the high accuracyof measurements, carried out using a computer program for 3D modeling "3ds Max".When combining the obtained linear dimensions of the damage with increased accuracyand the possibility to conduct retrospective diagnosis of the most specific part of thewound canal, formed by the blade belly, the level of accuracy and visualization of thecarried out forensic medical examination is significantly increased.Conclusions. The results, obtained by photogrammetry and 3D modeling of the woundcanal, make it possible to assert the increased accuracy of investigations of individualmorphological characteristics of the lesions and allow to conduct retrospectiveidentification of fragments of the wound canal with the instrument of injury. In additionto that, forensic medical experts receive a modern objective tool for the selection andidentification of the used stab- cutting tool among those provided for examination byjudicial investigation organs. The introduction of the modern methods of 3D modelinginto forensic medical and medical-criminal practice allows to improve the accuracyand visualization of the carrying out examinations and brings them to a new higherlevel.