Using the iPhone's LiDAR technology to capture 3D forensic data at crime and crash scenes

Background: Three-dimensional (3D) documentation of crime and crash scenes is common practice during forensic and medicolegal investigations. Such documentation at a scene is usually carried out by specially trained personnel using various 3D imaging devices and methods, such as terrestrial laser scanners. Unfortunately, this causes the implementation of 3D documentation at the scenes to be expensive and not readily accessible. In 2020, Apple introduced a light detection and ranging (LiDAR) sensor into their high-end mobile devices. In 2022, Recon-3D, an iOS application (app), was launched. This app turns an iPhone or iPad into a 3D scanner and is specifically targeted at crime and crash scene applications. Objectives: The aim of this study was to test the Recon-3D app based on exemplary scenarios to see whether this technology is generally applicable to document crime or crash scenes. Materials and Methods: An iPhone 13 Pro in combination with the Recon-3D app was used to document two indoor scenarios, a mock-up crime scene and a garage, as well as an outdoor scenario of a parked car. Each scenario was documented multiple times. Results: On average, data acquisition for one scene took less than 2 min. Known distances within the scenes were measured with a mean absolute error of 0.22 cm and a standard deviation of 0.18 cm. Conclusion: The imaging workflow was simple and quick, enabling any person to perform 3D documentation at a crime or crash scene. Overall, Recon-3D appeared to be a useful application for forensic investigators

Sperm hunting on optical microscope slides for forensic analysis with deep convolutional networks – a feasibility study

Microscopic sperm detection is an important task in sexual assault cases. In some instances, the samples contain no or only low amounts of semen. Therefore, the biological material is transferred onto a glass slide and needs to be manually scanned using an optical microscope. This work can be very time consuming, especially when no spermatozoa is present. In such a case, the result needs to be validated. In this article we show how convolutional neural networks can perform this task and how they can reduce the scanning time by locating the sperm cells on images taken under the microscope. For this purpose, we trained a VGG19 network and a VGG19 variation with 1942 images, some containing sperm cells and some not

Beyond the visible spectrum – applying 3D multispectral full-body imaging to the VirtoScan system

Multispectral photography offers a wide range of applications for forensic investigations. It is commonly used to detect latent evidence and to enhance the visibility of findings. Additionally, three-dimensional (3D) full-body documentation has become much easier and more affordable in recent years. However, the benefits of performing 3D imaging beyond the visible (VIS) spectrum are not well known, and the technique has not been widely used in forensic medical investigations. A multicamera setup was used to employ multispectral photogrammetry between 365 and 960 nm in postmortem investigations. The multicamera setup included four modified digital cameras, ultraviolet (UV) and near-infrared (NIR) light sources and supplemental lens filters. Full-body documentation was performed in conjunction with the use of a medical X-ray computed tomography (CT) scanner to automate the imaging procedure. Textured 3D models based on multispectral datasets from four example cases were reconstructed successfully. The level of detail and overall quality of the 3D reconstructions varied depending on the spectral range of the image data. Generally, the NIR datasets showed enhanced visibility of vein patterns and specific injuries, whereas the UV-induced datasets highlighted foreign substances on the skin. Three-dimensional multispectral full-body imaging enables the detection of latent evidence that is invisible to the naked eye and allows visualization, documentation and analysis of evidence beyond the VIS spectrum

VirtoScan-on-Rails – an automated 3D imaging system for fast post-mortem whole-body surface documentation at autopsy tables

Two-dimensional photographic documentation is a substantial part of post-mortem examinations for legal investigations. Additional three-dimensional surface documentation has been shown to assist in the visualization of findings and contribute to the reconstruction of the sequence of events. However, 2D photo documentation and, especially, 3D surface documentation, are time-consuming procedures that require specially trained personnel. In this study a 3D imaging system, called VirtoScan-on-Rails, was developed to automate and facilitate 3D surface documentation for photo documentation in autopsy suites. The imaging system was built to quickly acquire photogrammetric image sets of whole bodies during different stages of external and internal examinations. VirtoScan-on-Rails was set up in the autopsy suite of the Zurich Institute of Forensic Medicine at the University of Zurich (Zurich, Switzerland). The imaging system is based on a movable frame that carries a multi-camera array. Data quality and the applicability of the system were analyzed and evaluated within two test series. Up to 200 overlapping photographic images were acquired at consecutive image-capturing positions over a distance of approximately 2000 mm. The image-capturing process took 1 min and 23 s to acquire a set of 200 images for one side of the body. During test series one and two, 53 photogrammetric image sets taken from 31 forensic cases were successfully reconstructed. VirtoScan-on-Rails is an automated, fast and easy-to-use 3D imaging setup for autopsy suits. It facilitates documenting bodies during different stages of forensic examinations and allows standardizing the procedure of photo documentation

Multispectral 3D whole-body imaging of dressed and undressed bodies in combination with post-mortem x-ray computed tomography

Introduction: In the last few years, postmortem 3D body documentation, especially through the use of photogrammetry, has gained importance in the field of forensic medicine. For this purpose, conventional digital cameras are used to capture information within the visible part of the electromagnetic spectrum (i.e., visible light). Moreover, the use of multispectral photography allows the detection and documentation of traces and injuries, for instance, in the ultraviolet (UV) or near-infrared (NIR) range, which are otherwise invisible to the human eye. Although multispectral photography offers a wide range of applications for legal investigations, multispectral photogrammetry is not yet well known or widely used within the field of forensic medicine. Therefore, within this study and the framework of the VirtoScan project, a method for multispectral whole-body photogrammetry was developed and evaluated. Materials and Methods: A multicamera setup based on four modified digital single-lens reflex cameras, different light sources, and additional lens filters was mounted on a mobile wooden frame. The setup was used in combination with a medical X-ray computed tomography (CT) scanner. Automatic table movement from the CT scanner was used to capture consecutive image sets of the body from head to toe. In addition to standard photogrammetry within the visible range, multispectral photogrammetry was performed under UV and NIR light sources at 365 nm, 400 nm, 860 nm and 960 nm on undressed human bodies and under blue light and NIR light sources at 450 nm and 860 nm on dressed mannequins. After the multispectral photogrammetry procedure was finished, a whole-body CT scan was conducted to capture the internal information of the human body. Results: Multiview 3D reconstructions based on multispectral image data from four forensic cases and four different sets of dressed mannequins were carried out successfully. The overall quality and level of detail of the polygon models from the undressed bodies varied with regard to the spectral range of the image data. Dressed bodies captured under blue and visible light exhibited reduced quality and reduced level of detail on the polygon models within areas of dark-colored clothing. Whole-body photogrammetry for undressed bodies took approximately 5 min under UV illumination and approximately 3 min under visible light or NIR illumination. Whole-body photogrammetry for dressed bodies took approximately 12 min under blue-light illumination and approximately 4 min under visible light or NIR illumination. Discussion and Conclusion: The multispectral camera setup allows the capture of whole body datasets in an extended spectral range within a few minutes. With the help of photogrammetry software, textured 3D models for different spectral ranges can be reconstructed. Multispectral 3D whole-body imaging in line with postmortem CT examinations allows the combination of multispectral information from external body documentation with radiological findings from internal body documentation. Multispectral 3D documentation extends the postmortem forensic documentation of the deceased, as it detects (and documents) latent evidence on the body and textiles and can assist in detecting subcutaneous injuries and bruises on the body

Annular distribution patterns of .357 Magnum fragments in soft tissue simulants after striking hard material that prevented the bullet from exiting

The distribution of bullet fragments inside the body can provide information for the reconstruction of events in shooting incidents. The formation of an annular distribution pattern of bullet fragments was recently presented in a case report. The fragments were scattered radially around an exit-re-entrance wound resulting from collision of the bullet with a floor tile immediately after perforating the body. Such an annular distribution pattern of bullet fragments around an exit-re-entrance wound would indicate that a body was in close contact with hard material, for instance, lying on hard ground or leaning against a concrete wall, when the shot was fired. The aim of this experimental study was to investigate the formation and reproducibility of the annular distribution pattern of bullet fragments. It was assumed that the distribution pattern would be formed when hard material blocks a bullet from exiting a soft tissue simulant. Furthermore, the dependency of this distribution pattern on the impact angle was assessed. For this purpose, .357 Magnum bullets were fired at ballistic soap blocks with a steel plate at the rear end of the soap block. Six shots were performed at an impact angle of 90° (experiment 1), and six shots were performed at an impact angle of 45° (experiment 2). The distribution pattern of the fragments inside the individual soap blocks was examined via computed tomography (CT). In experiment 1, the bullets burst, and large fragments formed annular distribution patterns with a radial extent of approximately 4.9 cm and a maximum depth of approximately 2.3 cm. In experiment 2, the bullets ricocheted from the steel plate, and tiny fragments formed small annular distribution patterns at the points of ricochet with a radial extent of approximately 1.5 cm and a maximum depth of approximately 1.2 cm. The end position of the large main fragments was approximately 9.7 cm distant from the point of ricochet at a mean depth of 2.7 cm. The mean kinetic energy of the bullets at the time of impact was 580 J in experiment 1 and 394 J in experiment 2. Distribution patterns of bullet fragments in the body may provide information not only on the impact angle of a bullet but also on whether the body was in contact with a hard material that blocked the bullet from exiting the body. CT proved to be an appropriate imaging method for such investigations