Fall from a balcony--accidental or homicidal? Reconstruction by numerical simulation

Applicability of the Madymo Pedestrian Model for forensic fall analysis

Forensic reconstruction and scenario evaluation are crucial in investigations of suspicious deaths related to falls from a height. In such cases, distinguishing between accidental falls, being pushed or jumping is an important but difficult task, since objective methods to do so are currently lacking. This paper explores the possibility of repurposing a passive rigid body model of a human from commercially available crash simulation software for forensic reconstruction and scenario evaluation of humans dropping from heights. To use this approach, a prerequisite is that the human body model can produce realistic movements compared to those of a real human, given similar environmental conditions. Therefore, this study assessed the validity of the commercially available Simcenter Madymo Pedestrian Model (MPM) for simulating human fall movements. Experimental kinematic and kinetic data was collected from nine participants, who dropped from a height in three different ways: passively tilting over, getting pushed, and jumping. Next, the performance of the MPM in reproducing the kinematics of the experimental falls was assessed by comparing the orientation of the body 0.3 s after platform release. The results show that the MPM currently does not consistently reproduce the experimentally recorded falling movements across multiple falling conditions and outcome measures. The MPM must therefore be adapted if to be used for forensic reconstruction and scenario evaluation, for example by implementing active movement.

Body-kun/body-chan style model figures for artists in forensic visualization applications

Posture and body position are often in the focus of forensic medicine. Visualization for the purposes of documentation, teaching, scientific presentation or expert opinion in court is often desired. Plenty of possible tools to support visualization are available. However, there is a significant gap between quick drawings and more complex techniques. Body-chan (female) and body-kun (male) artist's model figurines (genericized trademark) may provide a useful means to fill this gap. These models, about 12-15 cm in height, are multi-articulated humanoids of realistic proportions, intended to serve as models for manga (japanese comic) drawing. Plenty of different models are available in different quality which usually are equipped with interchangeable hand and feet attachments, a frame for 'levitating' positions as well as assorted objects to scale. These inexpensive models may be positioned quickly and intuitively. Photodocumentation from various angles can be performed using a mobile phone camera. Images may be further improved applying digital image manipulation software. Taken together, the process is quick and intuitive and the level of achievable complexity is sufficient for many forensic applications.

Characteristic analysis and reconstruction method of falls from windows

Fall accidents from windows usually start indoors, so it is impossible to secure witnesses or video clips of the initial fall situation, and there are difficulties such as a complicated fall process, but related studies are rare. In this study, the types of window fall accidents are classified, and behavior characteristics are analyzed through multibody simulation analysis based on the initial fall postures and speed values from the experimental results. And, in case studies of carefully selected real events, a method for specifying the type of window fall accident is presented along with the reconstruction simulation results using a fuzzy tool for type estimation. It is believed that the results of the characteristic analysis for each type of window fall accidents and the reconstruction method proposed in this paper will be useful for related forensic investigations.

Slip and tilt: modeling falls over railings

Falls over railings are frequent case scenarios forensic experts are confronted with. An important issue is the differentiation of accidental and non-accidental falling scenarios. From a biomechanical point of view, this is a challenging task and should be addressed in a multifactorial approach. This work presents a simplified mechanical model in terms of a cranked rod that can be used in cases without relevant dynamic components in terms of pushing or jumping. If the anti-slip and the anti-tilt condition are violated, the possibility for a person to get over a railing should be assumed and investigated in more detail. Because our approach also involves uncertainties, the formulae should be understood to be part of a multifactorial approach. Numerical simulation, experimental reconstruction, injury pattern, and trace analysis can yield additional substantial connecting facts.

Characteristic analysis and fuzzy simulation of falls-from-height mechanics, and case studies

In this paper, methods for scientifically inferring the causes of the falls-from-height accidents, that is, the initial fall postures, and reconstructing the fall accident are presented. For this purpose, the general types of fall were subdivided into eight, and the characteristics of each fall type were analyzed. An initial posture estimation tool based on Fuzzy method was developed utilizing the massive amount of quantitative database that was constructed by repeating the simulation program for all types of falls. In addition, the initial conditions for each type were standardized with the experimental results and simulation data to reconstruct the fall behavior using the estimated fall accident type. The results of four carefully selected case studies were presented to verify the reliability and practicality of the developed fall analysis program and the reconstruction method.

Multibody Models for the Analysis of a Fall From Height: Accident, Suicide, or Murder?

The final subject position is often the only evidence in the case of the fall of a human being from a given height. Foreseeing the body trajectory and the respective driving force may not be trivial due to the possibility of rotations and to an unknown initial position and momentum of the subject. This article illustrates how multibody models can be used for this aim, with specific reference to an actual case, where a worker fell into a stair well, prior to stair mounting, and he was found in an unexpected posture. The aim of the analysis was establishing if this worker was dead in that same place, if he had been pushed, and which was his initial position. A multibody model of the subject has been built ("numerical android"), given his stature and his known mass. Multiple simulations have been performed, following a design of experiments where various initial positions and velocity as well as pushing forces have been considered, while the objective function to be minimized was the deviation of the numerical android position from the actual worker position. At the end of the analysis, it was possible to point how a very limited set of conditions, all including the application of an external pushing force (or initial speed), could produce the given final posture with an error on the distance function equal to 0.39 m. The full analysis gives a demonstration of the potentiality of multibody models as a tool for the analysis of falls in forensic inquiries.

Effect of Wind on Horizontal Displacement of Fatal Fall from a Height

The horizontal displacement of the human body resulting from fatal fall from a height is an important variable commonly used to inversely determine the cause or identify other forensic aspects of the fall. When examining the horizontal displacement, the wind effect is generally ignored. This technical note reports analytical modeling of the falling process, utilizing previous measurements of wind force acting on the human body, for determining the functional relationship between the wind speed and the horizontal displacement in the falling process. The result reveals that it does not take extremely rare wind conditions to cause a considerable shift of the human body, highlighting the importance to consider wind as a factor in investigations of fatal falls.

Forensic Application of Analytical Mechanics in Fatal Fall From a Height

Fatal fall from a height initiated with a swinging motion on the sagittal plane of the victim's body is examined. Method of analytical mechanics is adopted to establish the functional relations between the swinging angle of the body and the force needed to sustain the body until release, and the amount of the horizontal displacement that would occur after release. The analysis is applied to support an expert opinion presented in a criminal court in which two accused were convicted of murder for dropping a female victim from a bridge. The results indicate that it is unlikely for the body to locate as recorded by the police investigation report in the case. This study demonstrates that a straightforward mechanical analysis can be utilized to examine uncommon falling scenarios.