What does identification of clothing mean?

Even though garments are usually mass-produced, e.g. characteristics individualized by sewing processes or dyeings. If items of clothing are worn, they take on additional features due to the individual body shape of the wearer at certain body-related points, which can be seen, for example, in special wrinkle structures. A clothing examination should determine whether - an item of clothing matches or does not match an item of clothing on a photo or film - trace relationships between several clothing images can be recognized The examination is carried out by comparing any special features that may exist between an image of a person with their clothing and a similarly created image with the secured clothing. If no individualizing features are recognized due to the poor image quality or resolution, statements can be made regarding the clothing type, model or color, but the result value is lower. The result of the clothing examination results from the evaluation of the special features of the clothing and the photo or film recordings and any other features that may be present as well as their correspondences or deviations. First of all, the film or photographic material submitted for examination is viewed and checked for its suitability or evaluation options. The possibility of technical image enhancement must also be checked if recordings do not meet the necessary requirements. The most important image enhancement options include • Exposure compensation (global or local brightening so that more details become visible or darkening of bright areas to bring out details) • Color cast correction (e.g. reduction of yellow cast when taking pictures with artificial light or color change when taking infrared pictures) • Sharpening contours and surfaces There are often some special features to take into account when recording images and films. If the exterior lighting at the scene of the crime is greatly reduced, most color-transmitting surveillance cameras switch to black and white operation. With low-light cameras, this naturally occurs earlier than with high-speed devices. If there is a certain amount of basic lighting even in the dark (e.g. outdoor lighting, street lights, emergency light), high-performance cameras can remain in color operation both during the day and at night. Switching from color to b/w mode primarily means that not only is the color information lost, but depending on the camera there is also image noise and motion blur, which has a negative effect on the image or film quality. Depending on the technology level of the surveillance camera, the homogeneity of the illumination also plays a role. Older cameras have a well-lit image in the middle, but the edge areas are much darker and less clear, making comparisons difficult. A further influence on the recordings by older or low-priced cameras is overexposure, i.e. Areas of people or their clothing are shown very brightly, so that special features are not recognizable. In better surveillance cameras with IR LEDs, so-called adaptive exposure controls ensure light compensation, so that e.g. a person moving towards a surveillance camera with IR LEDs is not recorded overexposed. Even with items of clothing with reflective textiles, overexposure or changes in color can be seen in these areas. Reflective fabrics or textiles with reflective screen printing ink, reflective foils, reflector spray or similar treated look like normal fabrics in daylight, but glow as soon as an artificial light source hits. Additional fluorescent yarns (which do not reflect light, but produce more brilliant colors) increase the glare effect, so that in these and neighboring areas it may not be possible to use clothing individualities for identification or exclusion.

Examination procedure

The submitted clothing material is examined for special features. A distinction is made between group and individual characteristics. • group characteristics e.g. Basic shape, model, cut (pocket, collar, hem shape etc.), accessories, closure types and means • i ndividual characteristics Manufacturing and use-related peculiarities of the clothing e.g. Seams, damage during manufacture (used look) or through wear, dyeings, adhesions, accessories attached to the carrier The color of the clothing is only of limited use as a comparison criterion. Only a rough comparison can be made here, because color shades are difficult to determine due to the differently influenced photo recordings. The study is based on the principle that every item of clothing has the potential to differentiate itself from model-like items of clothing. The decisive factor is whether individualities found on the items of clothing are also visible on the items of clothing shown in the film and photo recordings, or whether the image quality limits or prevents them. In order to be able to make a comparison between the present item of clothing and a photograph, the item of clothing is, if possible, photographed from the same angle as at the crime scene. However, since it is usually impossible to exactly reproduce the lighting conditions at the crime scene, deviating light reflections on the photo of a surveillance camera can only be simulated to a limited extent during the examination. In most cases, even adjusting motion blur will not be the same. It is often sufficient to slip the clothing onto a mannequin. In some cases, however, it may be necessary to have the clothing worn by a similarly proportioned person in the comparison shots. The photo shoot from the crime scene (or the photo shoot generated from a film material) is compared with the comparison shot with the item of clothing from the photo laboratory. Matches or deviations are documented and recorded in a report.

Feature determination

Although clothing is largely mass-produced, it can often be differentiated based on special characteristics. In these cases, a distinction is made between characteristics of production and characteristics of use. Production characteristics are shown, for example, in the form of special: • seam patterns • seam defects • sample runs • grains in natural products • ripples • folds • manufacturer damage (used look) These are group-specific or individual. The usage features include in particular • wrinkles • wearing marks • damages • contaminations • repairs • other changes Their appearance in location, shape and size arises as a random product from an arbitrary interplay of different factors. It is not reproducible and therefore individual. It can therefore be assumed that clothing is already individual in detail due to production and at the latest shows obvious individualities through use. Artificial aging / used look Due to the fashion, some textiles should look old and used. This applies in particular to jeans items that are offered on the clothing market under the names: used, second life, authentic, destroyed, vintage, custom or dirty. There are physical-mechanical and chemical processes to bring about the effect of artificial aging. In the mechanical processes, washing processes with pumice stones or the like take several hours, which are put into the drum with the textiles. Higher areas of fabric and protruding seam edges are more worn or sanded and light-dark effects are created. There are also other manual interleaving cards e.g. through the so-called "sand blasting" (mixture of chlorine bleach and sand is sprayed onto the textile), the "ripping" (cutting with a blade) or the grinding (processing certain trouser areas with sandpaper). Chemical washes with, for example, chlorine bleach or hydrogen peroxide can partially or wholly bleach denim fabrics. The so-called "laser engraving" or "laser decoration" is a newer method of causing artificial aging. Here, previously defined pattern structures are transferred to the textile using laser burning.

identification of clothings /

image comparison

informative on the

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The resolution and quality of surveillance cameras is getting better and better. Recordings that previously could not be evaluated now allow identifications. The time when cameras with 640 x 480 (0.4 MegaPixel) small SD resolution were used is almost over. With this technique, clothing and faces were poorly or not recognizable at all. Surveillance cameras without HD are no longer suitable for distances further than three meters or for large areas. The so-called '1K cameras' (under 2 megapixels) are used as AHD, SDI or IP cameras and fortunately are hardly used anymore. Since 2016, 2K cameras (4 megapixels) including a good night vision function and 4K cameras (8 megapixels) have prevailed since 2018. These surveillance cameras are generally well suited for clothing identification (Tosi-Net network cameras or as wireless Tosi-Electricity-Powerline cameras). Additional lighting, which is usually in the infrared light range that is not visible to the human eye, is required so that pictures can still be taken in the dark. With infrared images, however, not only the color information is lost, there is also a color change or even color reversal. Light colors can suddenly appear dark and dark textile colors are shown brightly. Comparative information such as textile samples is often no longer recognizable. Even with items of clothing with reflective textiles, overexposure or changes in color can be seen in these areas. Reflective fabrics or textiles with reflective screen printing ink, reflective foils, reflector spray or similarly treated look like normal fabrics in daylight, but glow as soon as an artificial light source hits. Additional fluorescent yarns (which do not reflect light, but produce more brilliant colors) increase the glare effect, so that in these and neighboring areas it may not be possible to use clothing individualities for identification or exclusion. The so-called "laser engraving" or "laser decoration" is a newer method of causing artificial aging. Here, previously defined pattern structures are transferred to the textile using laser burning . In January 2020, the article 'Assessing the reliability of a clothing-based forensic identification' by Sophie J. Nightingale and Hany Farid was published. It is about FBI experts who analyzed the surveillance images of crime scenes and assigned them to the clothing of the perpetrators. It was about similarities in the wear marks along the seams. The two authors carried out a black box test with regard to these seam structures and proved with their means that no specific assignment was possible from some positions. This test has also been read with great care by the experts in Germany. There are a variety of ways to give jeans a used look. These hand-made changes are an individual feature in detail.