Photogrammetrische Auswertung von Haut- und Weichteilwunden sowie Knochenverletzungen zur Bestimmung des Tatwerkzeuges — grundlegende Aspekte

The forensic holodeck - Recommendations after 8 years of experience for additional equipment to document VR applications

The forensic holodeck was first introduced in 2013, using the first upcoming commercially available virtual reality gaming headsets to visualize forensic 3D reconstructions. Following the publication of this development virtual reality was introduced in case work in a variety of different ways. After 8 years of using virtual reality in a professional forensic capacity this professional practice report will show, which equipment is necessary in addition to a virtual reality setup. This mostly includes audio-visual and broadcasting technology for complete documentation of the application of virtual reality, but also some other IT equipment, which should be available for as low as 20'000 US$. Guidelines, hints and tips regarding equipment acquisition, setup and use will be provided and discussed.

[The diagnostic potential of computed tomography for the purpose of forensic medical examination of a craniocerebral injury]

The authors make use of the data borrowed from the special literature and the results of their original investigations to carry out the comparative analysis of the materials of the intravital X-ray studies and post-mortem examinations. Special attention is given to the possibilities available at the present time for making virtopsies in the cases of the craniocerebral injury.

Validation and evaluation of measuring methods for the 3D documentation of external injuries in the field of forensic medicine

Three-dimensional (3D) measurement techniques are gaining importance in many areas. The latest developments brought more cost-effective, user-friendly, and faster technologies onto the market. Which 3D techniques are suitable in the field of forensic medicine and what are their advantages and disadvantages? This wide-ranging study evaluated and validated various 3D measurement techniques for the forensic requirements. High-tech methods as well as low-budget systems have been tested and compared in terms of accuracy, ease of use, expenditure of time, mobility, cost, necessary knowhow, and their limitations. Within this study, various commercial measuring systems of the different techniques were tested. Based on the first results, one measuring system was selected for each technique, which appeared to be the most suitable for the forensic application or is already established in forensic medicine. A body of a deceased, a face and an injury of a living person, and a shoe sole were recorded by 11 people with different professions and previous knowledge using the selected systems. The results were assessed and the personal experiences were evaluated using a questionnaire. In addition, precision investigations were carried out using test objects. The study shows that the hand-held scanner and photogrammetry are very suitable for the 3D documentation of forensic medical findings. Their moderate acquisition costs and easy operation could lead to more frequent application in forensic medicine in the future. For special applications, the stripe-light scanner still has its justification due to its high precision, the flexible application area, and the high reliability. The results show that, thanks to the technological advances, the 3D measurement technology will have more and more impact on the routine of the forensic medical examination.

Skin injury model classification based on shape vector analysis

Background: Skin injuries can be crucial in judicial decision making. Forensic experts base their classification on subjective opinions. This study investigates whether known classes of simulated skin injuries are correctly classified statistically based on 3D surface models and derived numerical shape descriptors.

Methods: Skin injury surface characteristics are simulated with plasticine. Six injury classes – abrasions, incised wounds, gunshot entry wounds, smooth and textured strangulation marks as well as patterned injuries - with 18 instances each are used for a k-fold cross validation with six partitions. Deformed plasticine models are captured with a 3D surface scanner. Mean curvature is estimated for each polygon surface vertex. Subsequently, distance distributions and derived aspect ratios, convex hulls, concentric spheres, hyperbolic points and Fourier transforms are used to generate 1284-dimensional shape vectors. Subsequent descriptor reduction maximizing SNR (signal-to-noise ratio) result in an average of 41 descriptors (varying across k-folds). With non-normal multivariate distribution of heteroskedastic data, requirements for LDA (linear discriminant analysis) are not met. Thus, shrinkage parameters of RDA (regularized discriminant analysis) are optimized yielding a best performance with λ = 0.99 and γ = 0.001.

Results: Receiver Operating Characteristic of a descriptive RDA yields an ideal Area Under the Curve of 1.0for all six categories. Predictive RDA results in an average CRR (correct recognition rate) of 97,22% under a 6 partition k-fold. Adding uniform noise within the range of one standard deviation degrades the average CRR to 71,3%.

Conclusions: Digitized 3D surface shape data can be used to automatically classify idealized shape models of simulated skin injuries. Deriving some well established descriptors such as histograms, saddle shape of hyperbolic points or convex hulls with subsequent reduction of dimensionality while maximizing SNR seem to work well for the data at hand, as predictive RDA results in CRR of 97,22%. Objective basis for discrimination of non-overlapping hypotheses or categories are a major issue in medicolegal skin injury analysis and that is where this method appears to be strong. Technical surface quality is important in that adding noise clearly degrades CRR.

Trial registration: This study does not cover the results of a controlled health care intervention as only plasticine was used. Thus, there was no trial registration.

Traumatologie und gewaltsamer Tod

Vorgeschichte: Eine 39 Jahre alt gewordene, alkoholabhängige Frau habe von ihrem Hausarzt eine Packung Distraneurinkapseln (25 Stück) verschrieben bekommen; sie solle morgens und mittags je 1, abends 2 Kapseln einnehmen. Aus der Apotheke zurück gekehrt, begann sie zu Hause, mit ihrem Ehemann Alkohol zu trinken. Es sei zu einem Streit gekommen, in dessen Verlauf die Frau die Polizei angerufen habe. Der Ehemann sei daraufhin gegen 17.00 Uhr in Gewahrsam genommen und zur Wache verbracht worden. Ein Atemalkoholtest habe einen Atemalkoholwert von 1,29 mg/l ergeben. Gegen 04.00 Uhr morgens sei der Ehemann wieder entlassen worden (!). Er selbst habe angegeben, seine Ehefrau schlafend auf dem Sofa angetroffen zu haben; er habe sie geweckt, sie habe u.a. zu ihm gesagt, dass sie die Distraneurintabletten eingenommen habe. Ihr Zustand habe sich deutlich von dem bei sonstiger Alkoholisierung unterschieden. Gegen 05.30 Uhr habe er den Notarzt verständigt, der nur noch den Tod feststellen konnte.

VIRTOPSY: minimally invasive, imaging-guided virtual autopsy

Invasive "body-opening" autopsy represents the traditional means of postmortem investigation in humans. However, modern cross-sectional imaging techniques can supplement and may even partially replace traditional autopsy. Computed tomography (CT) is the imaging modality of choice for two- and three-dimensional documentation and analysis of autopsy findings including fracture systems, pathologic gas collections (eg, air embolism, subcutaneous emphysema after trauma, hyperbaric trauma, decomposition effects), and gross tissue injury. Various postprocessing techniques can provide strong forensic evidence for use in legal proceedings. Magnetic resonance (MR) imaging has had a greater impact in demonstrating soft-tissue injury, organ trauma, and nontraumatic conditions. However, the differences in morphologic features and signal intensity characteristics seen at antemortem versus postmortem MR imaging have not yet been studied systematically. The documentation and analysis of postmortem findings with CT and MR imaging and postprocessing techniques ("virtopsy") is investigator independent, objective, and noninvasive and will lead to qualitative improvements in forensic pathologic investigation. Future applications of this approach include the assessment of morbidity and mortality in the general population and, perhaps, routine screening of bodies prior to burial.

Clinical forensic medicine and its main fields of activity from the foundation of the German Society of Legal Medicine until today

The fields mainly covered by clinical forensic medicine are subject to time-related changes which are described on the basis of the German literature of the 20th century. Some fields of forensic sexual medicine (diagnosis of virginity, proof of criminal abortion, potentia coeundi, potentia generandi, potentia concipiendi) have become less important in the daily work of medicolegal institutes, whereas victims of rape and sexual abuse continue to form a major part of the forensic examination material in the German-speaking countries. The evaluation of suspected physical child abuse has grown in importance since the 60s, and it is essentially the merit of Elisabeth Trube-Becker that this problem is now dealt with also in scientific medicine. More recently, medicolegal experts are increasingly confronted with further groups of persons: victims of domestic violence, abused/neglected seniors, refugees from countries where torture is used. A new special field, which established itself only in the 90s, is the estimation of age with regard to the criminal responsibility of suspects who have no identity papers or pretend to have none. A phenomenon frequently observed in the last two decades is the non-accidental self-infliction of injuries. Whereas in the first half of the 20th century the motive for self-mutilation was typically to evade military service, this category of injury was later mainly seen in the context of insurance fraud; more recently most forensically relevant self-inflicted injuries refer to simulated offenses (fictitious sexual offenses and robbery, attacks allegedly having a political background). One of the traditional fields of clinical forensic medicine continues to be the evaluation of victims and suspects following bodily harm and attempted homicides. In the field of civil law medicolegal experts are particularly often concerned with controversial consequences of traffic accidents (e.g. alleged whiplash injuries after rear-end collisions at low velocities).

Analysis of patterned injuries and injury-causing instruments with forensic 3D/CAD supported photogrammetry (FPHG): an instruction manual for the documentation process

Forensic 3D/CAD supported photogrammetry (FPHG) is a method of recording and documenting the surface of small objects, thus enabling a three-dimensional image of these objects in virtual space. With this representation on the computer screen the course of forensically relevant events can be reconstructed. The procedure allows for examining patterned injuries of skin, soft tissue or bones for matching potentially incriminated instruments in shape, size and angle.3D recording of objects to be examined requires taking series of photographs. A computer system then calculates the position in space of certain points on the surface of the objects and subsequently produces 3D data models of the objects. Using a 3D/CAD program these data models are used to generate graphic true-to-object volume models. The objects in question can then be moved against each other arbitrarily on the screen-depending on the questions to be answered-in order to compare them and possibly establish their congruence. This article covers the state of the art in FPHG procedures in the form of a step-by-step instruction. It also illustrates the wide range of FPHG applications.

Matching tire tracks on the head using forensic photogrammetry

In the field of the documentation of forensics-relevant injuries, from the reconstructive point of view, the forensic, CAD-supported photogrammetry plays an important role; particularly so when a detailed 3-D reconstruction is vital. This is demonstrated with a soft-tissue injury to the face caused by being run over by a car tire. Since the objects (injury and surface of the tire) to be investigated will be evaluated in virtual space, they must be series photographed. These photo sequences are then evaluated with the RolleiMetric multi-image evaluation system. This system measures and calculates the spatial location of points shown in the photo sequences, and creates 3-D data models of the objects. In a 3-D CAD program, the model of the injury is then compared against the model of the possible injury-causing instrument. The validation of the forensic, CAD-supported photogrammetry, as shown by the perfect 3-D match between the tire tread and the facial injury, demonstrates how greatly this 3-D method surpasses the classic 2-D overlay method (one-to-one photography).

Streifenlichttopometrie (SLT): a new method for the three-dimensional photorealistic forensic documentation in colour

By means of the new method of Streifenlichttopometrie (SLT) it is possible to record the complete body surface of casualties in a practically photorealistic fashion, i.e. three-dimensionally and in colour. In comparison with the classic method of Photogrammetry Streifenlichttopometrie (SLT) is remarkably faster (10,000 points/s instead of 1 point/s) and in addition the colour of every point measured upon the corpse's surface is instantly recorded. Taking into consideration the resolution required and the qualities of the camera system the body surface is recorded in 'patches', i.e., areas of a defined extension (in the present case 500 mmx500 mmx200 mm) which are marked with a body fixed reference frame to grant the exact matching of the data after the recording process. Length, perimeter, square and volume of the body segments and injuries can be determined. Furthermore the natural colour of the wounds can be used for an immediate classification according to the intensity of the impact forces. In addition the 3-D coordinates of the body surface including the wounds can be transferred into an animated computer simulation for the reconstruction of the traumatic events.