Determination of average vehicle speed utilizing reverse projection

Reverse projection photogrammetry has long been used to estimate the height of an individual in forensic video examinations. A natural extrapolation would be to apply the same technique on a video to estimate the speed of an object by determining the distance traveled between two points over a set amount of time. To test this theory, five digital video recorders (DVRs) were connected to a single fixed camera to record a vehicle traveling down a track. The vehicle's speed was measured through Doppler radar by a trained operator and the speedometer of the vehicle was also recorded with a video camera. The recorded video was examined and the frames that best depict the beginning and end of the vehicles course were selected. Two reverse projection photogrammetric examinations were performed on the selected frames to establish the position of the vehicle. The distance between the two points was measured, and the time elapsed between the two points was examined. The outcome provided an accurate speed result with a standard degree of uncertainty. This study proves the feasibility of using video data and reverse projection photogrammetry to determine the speed of a vehicle with a limited set of variables. Further research is needed to determine how additional variables would impact the standard degree of uncertainty.     

Photogrammetry vs CT Scan: Evaluation of Accuracy of a Low-Cost Three-Dimensional Acquisition Method for Forensic Facial Approximation

Photogrammetry is a three-dimensional acquisition method potentially applicable to the forensic field. This possibility requires the verification of its accuracy. In this study, 3D volumes of skulls are generated to compare the photogrammetry versus the CT scan. In order to provide eligible material to the photogrammetric software, photographs were captured at a distance of 30 cm from the skull placed on a support 1 m in height and illuminated with diffused laboratory ceiling artificial light. A Nikon Coolpix P7100 camera was used. Photographs capture common elements with the previous and the next photograph so as to allow the photogrammetric software to recognize these common points between photographs and create a 3D puzzle. The Zephyr Lite (3DFlow©) software was employed to register the 3D volume. CT-based skulls are taken as a metric reference. The photogrammetry-based skulls are then enlarged according to the measurements of some landmarks or Zygion and Zygion, the distance between end of nasal and base of nasal pyramid for frontal projection, and minimum breadth of the mandibular ramus for the right lateral projection. The accuracy of the photogrammetry is compared to that of the CT scan by measuring the 3D volumes of the skulls studied. Specific landmarks are used as reference points for the measures in both frontal and lateral views. Bland–Altman graph shows homogeneity. The mean difference (1.28 mm) indicates that the measurements taken on the photogrammetry-based skull tend to slightly overestimate compared with the measurements taken on the CT-based skull.     

监控视频中车辆平均速度测算方法比较

根据车辆速度计算公式,提出了两种基于监控视频测速的思路。一是视频图像与实地测量相结合,车辆运动距离通过与监控画面匹配后实地测量,运动时间通过视频帧率运算分别获得。二是利用车辆技术参数测量,在视频图像中,车身前后明显部位经过同一点,车辆运动距离和时间分别通过被测车型技术参数、视频帧率运算获得。并通过实验结果对两种方法进行评价。     

视频方法鉴定车速的准确性研究

目的通过实验研究用视频方法鉴定车速结果的准确性及其影响因素。方法在选定的实验场地上,让实验车辆以一定速度匀速通过一段距离,使用高空、垂直、斜角和车载四个位置的摄像机同时录制,将车速计算结果进行比较。结果理论和实验数据分析表明,误差的大小主要取决于:车速和帧速率,车体上参考点和路上参考点的对齐效果,还有行车距离的大小和播放器屏幕的大小等。结论用视频方法进行车速鉴定,相对于传统的用力学公式进行计算,其准确性和可信度较好;一般条件下,误差可在5%~10%之间估算;夜晚条件下,可在车灯的轮廓线上选择车体上参考点,炫目情况除外。     

Simulation-based reconstruction of traffic incidents from moving vehicle mono-camera

Video recordings from digital cameras implemented in road vehicles present a valuable source of data concerning various dangerous traffic situations, i.e., road accidents or near-miss incidents. This data is readily available and numerous methods for forensic reconstruction of traffic situations from vehicle video were presented in the past. New alternative method for reconstruction of traffic situations from vehicle video is presented in this article. The method is based on the fusion of kinetic vehicle trajectory simulation within 3D laser scanner point cloud, projective geometry, and processing of video footage from moving vehicle camera. The method offers accurate reconstruction of general vehicle motion within relevant time domain whereby in-depth technical information about traffic incident can be quantitatively extracted from video footage. The result is physics-based 3D projection of simulated vehicle motion on the motion of real vehicle recorded by moving monocular camera. The method was validated within performed experimental test runs with respect to vehicle speed, distance travelled, acceleration/deceleration and directional quantities (yaw rate, yaw angle). The method was further applied in the reconstruction of real-world traffic events.     

Determination of vehicle speed from recorded video using the open-source software Kinovea

Video devices of different kind often record traffic accidents, including vehicle-pedestrian collisions and hit-and-run accidents. In these cases, the vehicle speed is valuable information because it can assist the investigators in an accident reconstruction. This paper examines the use of Kinovea, an open-source video annotation tool designed for sport analysis, to estimate vehicle speed in forensic videos. Kinovea does not require a complex methodology, and it can be used to make the calculation easily. A series of vehicle driving experiments using an appropriately calibrated speed radar system (so called Scout Speed) were carried out, and measurements were compared with the estimated speed. In controlled conditions, the comparison of Scout reference speed and calculated average vehicle speed by means of Kinovea found an average difference of 0.43 km/h, with a margin of error of ±0.64 km/h. In addition, further preliminary tests were carried out to check the reliability of the measurements under lower resolution conditions. Also, in these cases the calculations were in line with the ground truth. Therefore, in the tested conditions, Kinovea demonstrated to be an easy and reliable tool available for forensic video examiners. Further tests need to be conducted in order to address the applicability of the measurement technique with true CCTV/surveillance video recordings.     

基于视频的车速鉴定方法

视频监控设备的广泛应用为各类案件的侦破及取证提供了重要线索。利用高质量视频图像进行近景摄影测量、运动物体识别及跟踪的方法和技术已经较为成熟,但利用广角、低像素的视频监控录像定量描述车辆行驶速度的技术研究尚未开展。针对交通事故技术鉴定的实际需求,根据速度的一般计算方法和计算机视觉的基本原理,提出可以应用目前广泛使用的公共视频监控设备所拍摄的录像进行车辆速度计算的方法。     

Authentication of Surveillance Videos: Detecting Frame Duplication Based on Residual Frame

Nowadays, surveillance systems are used to control crimes. Therefore, the authenticity of digital video increases the accuracy of deciding to admit the digital video as legal evidence or not. Inter‐frame duplication forgery is the most common type of video forgery methods. However, many existing methods have been proposed for detecting this type of forgery and these methods require high computational time and impractical. In this study, we propose an efficient inter‐frame duplication detection algorithm based on standard deviation of residual frames. Standard deviation of residual frame is applied to select some frames and ignore others, which represent a static scene. Then, the entropy of discrete cosine transform coefficients is calculated for each selected residual frame to represent its discriminating feature. Duplicated frames are then detected exactly using subsequence feature analysis. The experimental results demonstrated that the proposed method is effective to identify inter‐frame duplication forgery with localization and acceptable running time.     

Photogrammetric Documentation of Regions of Interest at Autopsy—A Pilot Study

In this pilot study, the authors tested whether photogrammetry can replace or supplement physical measurements made during autopsies and, based on such measurements, whether virtual computer models may be applicable in forensic reconstructions. Photogrammetric and physical measurements of markers denoting wounds on five volunteers were compared. Virtual models of the volunteers were made, and the precision of the markers' locations on the models was tested. Twelve of 13 mean differences between photogrammetric and physical measurements were below 1 cm, which indicates that the photogrammetric method has a high accuracy. The precision of the markers' location on the models was somewhat less, although the method is still promising and potentially superior to the current procedures used for reconstructions. The possibility to measure any distance on a body, even after the autopsy is concluded and the corpse is no longer available, is one of the biggest benefits of photogrammetry.     

Forensic integrity verification of video recordings based on MTS files

Digital video is used in criminal trials as evidence with legal responsibility because video content vividly depicts events occurring at a crime scene. However, using sophisticated video editing software, assailants can easily manipulate visible clues for their own benefit. Therefore, the integrity of digital video files acquired or submitted as evidence must be ensured. Forensic analysis of digital video is key to ensuring the integrity of links with individual cameras. In this study, we analyzed whether it is possible to ensure the integrity of MTS video files. Herein, we propose a method to verify the integrity of MTS files encoded by advanced video coding high definition (AVCHD), which is frequently used for video recording. To verify MTS file integrity, we propose five features. Codec information, picture timing, and camera manufacture/model are modified AVI and MP4-like format video verification features. Group of pictures and Universally Unique Identifier patterns were specifically developed for MTS streams. We analyzed the features of 44 standard files recorded using all recording options of seven cameras. We checked whether integrity can be validated on unmanipulated videos recorded in various environments. In addition, we considered whether manipulated MTS files edited in video editing software could be validated. Experimental results show that all unmanipulated and manipulated MTS files with known recording devices were discriminated only when all five features were checked. These results show that the proposed method verifies the integrity of MTS files, strengthening the validity of MTS file-based evidence in trials.     

Suspect Height Estimation Using the Faro Focus3D Laser Scanner

At present, very little research has been devoted to investigating the ability of laser scanning technology to accurately measure height from surveillance video. The goal of this study was to test the accuracy of one particular laser scanner to estimate suspect height from video footage. The known heights of 10 individuals were measured using an anthropometer. The individuals were then recorded on video walking along a predetermined path in a simulated crime scene environment both with and without headwear. The difference between the known heights and the estimated heights obtained from the laser scanner software were compared using a one-way t-test. The height estimates obtained from the software were not significantly different from the known heights whether individuals were wearing headwear (p = 0.186) or not (p = 0.707). Thus, laser scanning is one technique that could potentially be used by investigators to determine suspect height from video footage.     

Validation of the New Interpretation of Gerasimov's Nasal Projection Method for Forensic Facial Approximation Using CT Data,

The most common method to predict nasal projection for forensic facial approximation is Gerasimov's two‐tangent method. Ullrich H, Stephan CN (J Forensic Sci, 2011; 56: 470) argued that the method has not being properly implemented and a revised interpretation was proposed. The aim of this study was to compare the accuracy of both versions using a sample of 66 postmortem cranial CT data. The true nasal tip was defined using pronasale and nasal spine line, as it was not originally specified by Gerasimov. The original guidelines were found to be highly inaccurate with the position of the nasal tip being overestimated by c. 2 cm. Despite the revised interpretation consistently resulting in smaller distance from true nasal tip, the method was not statistically accurate (p > 0.05) in positioning the tip of the nose (absolute distance >5 mm). These results support that Gerasimov's method was not properly performed, and Ullrich H, Stephan CN (J Forensic Sci, 2011; 56: 470) interpretation should be used instead.     

Empirical Evaluation of the Reliability of Photogrammetry Software in the Recovery of Three-Dimensional Footwear Impressions

This paper examines the reliability of Structure from Motion (SfM) photogrammetry as a tool in the capture of forensic footwear marks. This is applicable to photogrammetry freeware DigTrace but is equally relevant to other SfM solutions. SfM simply requires a digital camera, a scale bar, and a selection of oblique photographs of the trace in question taken at the scene. The output is a digital three-dimensional point cloud of the surface and any plastic trace thereon. The first section of this paper examines the reliability of photogrammetry to capture the same data when repeatedly used on one impression, while the second part assesses the impact of varying cameras. Using cloud to cloud comparisons that measure the distance between two-point clouds, we assess the variability between models. The results highlight how little variability is evident and therefore speak to the accuracy and consistency of such techniques in the capture of three-dimensional traces. Using this method, 3D footwear impressions can, in many substrates, be collected with a repeatability of 97% with any variation between models less than ~0.5 mm.     

A Review of Alcohol‐Impaired Driving: The Role of Blood Alcohol Concentration and Complexity of the Driving Task

The operation of a motor vehicle requires the integrity of sensory, motor, and intellectual faculties. Impairment of these faculties following the consumption of alcohol has been studied extensively through laboratory, closed‐course and on‐road driving, and epidemiological studies. The scientific literature was reviewed critically, with a focus on low‐to‐moderate blood alcohol concentrations (BAC ≤ 0.100%), to identify the most reliable determinants of alcohol‐impaired driving. Variables such as age, gender, driving skill, and tolerance were shown to have limited impact on impairment. It was concluded the most relevant variables are BAC and complexity of the driving task. The scientific literature provides a high degree of confidence to support the conclusion that a BAC of 0.050% impairs faculties required in the operation of a motor vehicle. Whether impairment is apparent depends upon the complexity of the driving task, which applies to both study design and actual driving.     

The Forensic Implications of Amphetamine Intoxication in Cases of Inflicted Blunt Craniocerebral Trauma

The effects of D‐amphetamine on outcome after blunt craniocerebral trauma are characterized and the potential legal implications discussed. Traumatic brain injury (TBI) was induced under general anesthesia in adult, male Sprague Dawley rats using the impact acceleration model. At 10 min prior to injury, D‐amphetamine (5 mg/kg) or saline vehicle was administered subcutaneously; animals were subsequently assessed over a 7‐day period post‐trauma for motor outcome using a rotarod device. D‐amphetamine treated animals performed significantly better (p < 0.001; ANOVA) than vehicle treated controls on their motor assessment, suggesting that D‐amphetamine exposure prior to injury either is neuroprotective or enhances motor performance. It is possible, therefore, that an individual who has taken amphetamines may function at a better motor level after head trauma than one who has not been exposed to the drug. Future interpretations of the potential effects of amphetamines on TBI should include this possibility.     

A Novel Pixel‐Based Method to Estimate the Instantaneous Velocity of a Vehicle from CCTV Images

In traffic forensic identifications, it was usually unfavorable that estimated velocities of questioned vehicles derived from frame‐based methods eventually turned out to be close to but a bit less than speed limits. In this paper, a novel pixel‐based method was presented to estimate vehicles’ relatively instantaneous velocities. First, two adjacent pixels’ actual distance was acquired from the closed‐circuit television (CCTV) images. Then, the instantaneous average velocity within this one frame interval time (FIT) was calculated out. The frame‐based method and its evaluating result were also introduced in this paper. The results showed that the velocity estimated by this new pixel‐based method was higher than which derived from the frame‐based method. Employing this presented novel method in these cases, it could be more accurately identified whether or not the vehicles had exceeded the speed limits, and then the responsibilities could be consequently assigned impartially.     

Viability of Human Articular Chondrocytes Harvested Postmortem: Changes with Time and Temperature of In Vitro Culture Conditions

Different studies of long‐term chondrocytes viability have shown a gradual reduction as a function of time and ambient temperature. The aim of our in vitro study was to establish chondrocyte postmortem viability curves for 4°C, 11°C, 23°C, 35°C during 63 days after the donors' death. Osteochondral cylinders were procured from the knees of 16 male donors (20–47 years), stored in preservation media that was not changed, and analyzed in 3‐day intervals using a confocal laser scanning microscope. A significant influence of time on viability was found from Day 9 (p = 0.0029) and onwards (p < 0.0001). The lowest overall chondrocyte viability was at 35°C, followed by 4°C (p < 0.0001). The conditions used in this in vitro analysis suggest that similar viabilities may occur while in situ in the decedent. Further studies of chondrocyte viability from individuals with known postmortem intervals may show premise to help evaluate time since death in the late postmortem interval.