Technical traces of form
As Technical form tracks changes in shape are referred to an object caused by a track setter. In criminology, conclusions can be drawn from the shape of the trace . The teaching of technical traces of form is also known as trassology .
Technical traces of form in criminalistic trace areas
Imprint traces result from loss of material (negative imprint) or from material application (positive imprint). The track carrier is usually smooth and hard. Loss of material means, for example, the removal of a layer of dust , oil or paint from the floor; the application of a foreign layer ( blood , sweat , tire rubber , etc.) to the track carrier under material application . A footprint trail is in criminology or accident research a track in which an object or person to track carrier has changed by direct contact. Often the change consists in the residue left behind, for example sweat and sebum on a fingerprint or rubber on a tire track.
Sliding marks form when a harder object slides over a softer object (material displacement or material loss). Important slip marks are: scratch marks, groove marks, notch marks - i.e. mostly marks from or on the tool.
Draw marks arise during the manufacturing of objects (mostly metal or glass ). In the melting state, individual characteristics, e.g. B. wear and tear of the nozzles transferred to the product; after hardening, they remain relatively even over a longer distance. In particular, they show which separate parts of a continuous production run belong together (e.g. wire, glass pane, metal rods).
Cutting marks are created by the transfer of individual features of the cutting tool to the trimmed or cut off trace carrier. The features can already have arisen during manufacture or through processing and wear and tear. Whether or not they are transmitted depends largely on the material of the trace carrier. Cut marks: knife , scissors , hatchet , ax , bolt cutter ; Pinch marks: pliers
Drilling marks are created when using a drill , also known as a drill bit . The usually harder tool or tool part creates circular holes in a generally softer material by machining. The resulting hole is called a hole. Both in the borehole and on the drilling chips, individual features of the drilling tool emerge as indentation marks.
Saw marks are created when cutting or notching wood , natural stone , metal , plastic and other solid materials through the use of a saw as a tool . The saw is a cutting tool, which due to the continuous movements of the saw teeth (for example, the circular saw ) or discontinuous movements of a hand saw (such as foxtail ) separating the softer material and disassembled. Individual features of the sawing tool can be seen on the groove or parting line of the material as well as on the sawdust.
Traces of breakage or cracks
Traces of breakage or cracks are caused by breaking or tearing off parts of material such as paper , adhesive tape , but also metal parts. The resulting pass marks allow conclusions to be drawn about the type and sequence of the impacting forces.
Pass marks show which individual parts of an object belonged together, e.g. B. broken glass, adhesive tape, broken knife blade. As a result of the application of force and force, parts break or tear randomly and cannot be reproduced. These parts can be placed against one another or fitted according to the material.
Manuscripts allow conclusions to be drawn about the author. The multi-level method determines the impression characters of a font according to the movement image (impulsive, powerful, erratic, dynamic, disturbed), form image (bizarre, original, inflated, round, stylized), spatial image (wide-meshed, torn, confused, clear) and line image (colored, warm, dry, strong, plastic). Furthermore, the relationship between movement and shape, degree of stiffness (tension of a font), rhythm, degree of individual character, uniformity are used to determine the overall characteristics of a font. Twenty individual features are recorded, some of which are measurable, estimable or describable (slow or hasty, unconnected or connected, small or large, lean or full).
Through the use of firearms occur at the weapons and ammunition parts ( projectile , shell a plurality of individual tracks). First and foremost, it must be checked whether seized ammunition parts from a certain firearm have been fired (so-called proof of fire). Other areas of investigation include the legal evaluation of weapons with regard to weapon law , evaluation of prohibited items, determination of the cause of weapon defects with information on hazards and injuries, determination of trigger weights, energy measurements and directions of fire.
Autogenous mold traces
Autogenous traces of shape are mainly caused by gravity deformation of the tracing material, e.g. B. rivulets, drip marks.
Other traces of shape
Technical traces of form in criminalistic types of traces
In police practice, these technical traces of form generally appear in the following types of traces:
- Tool marks
- Shoe marks
- Glove marks
- Vehicle tracks (including tire tracks)
- Pass marks
- Traces in locks
- Traces from the use of firearms
- Traces of accidents, accident reconstructions after serious traffic accidents
- removed embossing, such as B. Chassis numbers of motor vehicles that are made visible again by mechanical-chemical processes.
Investigation methods of technical traces of form
The investigation of the tracks is carried out with the aid of a plurality of optical aids, such as magnifying glass , borescope , measuring microscope , stereoscopic microscope , stereo comparison microscope and the use of extensive theoretical and practical knowledge in the fields of forensic tracing and quality assurance, the material and manufacturing customer, measuring and testing as well as general mechanics and optics .
When comparing tool traces, trace material relevant to the crime is compared under a comparison microscope. The stereo image is digitized by the adapted video camera and made available on the computer for further processing (archiving, expert opinions, etc.). This working method is also used when examining profile locking cylinders and fitting marks.
For a comparative examination, the "laying" or making of "comparative traces" is essential. After the trace analysis, taking into account the possible inspection method and the use of the experience of the experts in a wide variety of media
- Comparison prints (with shoes , gloves , tires ) and
- Comparison charts and impressions (with tools) made.
The "trace of the incident" and the "comparison trace" are then compared. The causal starting point for the possibility of a comparison are u. a. Production-related peculiarities in the manufacture of the trace cause (shoes, tires, gloves, tools) and the fact that these objects receive individual peculiarities in the course of their use due to mechanical and thermal effects as well as wear, which can be transferred to the trace carrier. If the peculiarities of the trace of the incident and the comparison trace match, in most cases the person who caused the trace can be specifically assigned to the corresponding trace (e.g. tools, shoes, etc.). The visual representation of test results in the case of shoe, glove and tire marks in the expert report is carried out using original photographs and comparative prints.
Traces of technical form in criminal collections
Shoe track databases
Computer-aided shoe trace databases are kept at the German state criminal police offices, which allow the comparison of incoming traces and perpetrators' shoes with open shoe traces contained here. For this purpose, the traces are read into the existing programs in the database using various input devices ( flatbed scanner , hand scanner , scan camera , video camera ) and linked to a data record. The precisely defined shaping of shoe profiles enables a research mode that summarizes and depicts similar trace patterns. After a rough analysis, measurements can be carried out in the program. In the event of a possible track match, further examinations are then carried out on the original tracks in question.
Passport track collections
Passage comparisons are often carried out after broken tool parts have been found at crime scenes , as well as vehicle parts at accident sites. The starting point for the expert's statement is the fact that parts break or tear arbitrarily and not reproducibly under the influence of force and force. The prerequisite for this is the determination of comparison tools and other vehicle parts.
In the investigation process, these parts are "fitted together" or "fitted" to one another, taking into account the morphology of the material. If this was successful, it has been proven that the relevant parts originally formed a unified whole. As with the other types of traces, the results of the examination are displayed graphically either through photos or video prints.
Tool track collections
Investigations of tools and tool marks are carried out for the purpose of proof of identity. It is determined whether a certain trace has been caused by a certain tool. Tool traces from so far unsolved crimes are located in tool trace collections at the federal German state criminal investigation offices. By comparing these traces of evidence, connections can be recognized. Suspect tools are compared with the traces of the tool trace collection.
Another area of responsibility is the examination of security devices, locks and keys for traces of manipulation or subsequent locking as well as traces of copying processes. This also includes the assessment of electronic locking systems and immobilizers. The area of lock and key technology extends from simple padlocks to high-quality safe locks.
Central firearms detection service at the Federal Criminal Police Office
Ammunition parts from seized firearms are compared in the Federal Criminal Police Office with the ammunition parts from unsolved crimes stored there in the central crime ammunition collection. The ammunition collection that currently about 5,000 bushes and about 5,000 bullets contains, is the recognition of Tatzusammenhängen and the identification of murder weapons. In the case of seized missed ammunition, the question arises as to whether the murder weapon has already been used in previous crimes, which is why one looks for individual traces of the weapon in the investigation of the ammunition. So-called comparison ammunition is obtained from seized weapons and compared with the collection.
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