A fatal fall from a balcony? A biomechanical approach to resolving conflicting witness accounts

An adult male was found below a third floor balcony having sustained fatal head injuries. An account provided by a witness described how the deceased had been in high spirits and had engaged in swinging from the third floor balcony rail in an attempt to swing onto a lower second floor balcony and whilst doing so had lost his grip and fallen (10.67 metres) to the ground below. A conflicting account was provided, some weeks later, by a second witness, who claimed to have observed an argument between two men on a third floor balcony, during which one had vigorously pushed the other over the balcony rail. The push, it was alleged, caused the man to move very quickly over the balcony rail and fall in an 'upturned crucifix' position to the ground. This paper describes a series of biomechanical experiments, conducted on a reconstruction of the third floor balcony and the second floor balcony rail, during which a volunteer was subjected to the two fall scenarios, in an attempt to resolve the conflicting witness accounts. Analysis of human movement was performed using a 3-D motion analysis system, markers were placed at the volunteer's key joint centres and were tracked to determine physical parameters. The parameter values were used to calculate what dynamic movements may have occurred had the volunteer been allowed to fall, not just a distance equivalent to the lower balcony rail but a greater distance, equivalent to that between the balcony and the ground. Calculations indicate that during the hanging-fall scenario a range of body rotation was produced between 159 degrees and 249 degrees, that is, an upturned head-first body orientation, consistent with that required to produce the described injuries and consistent with the description provided by the first witness. The push-fall scenario, however, produced a greater estimated body rotation of between 329 degrees and 530 degrees, equal to the body rotating, from the point of free-fall to the moment of impact, between almost 1 and 1.5 times. This was consistent with the described injuries but inconsistent with the description provided by the second witness. It was therefore concluded that although both the accidental and inflicted-push scenarios could produce a body orientation consistent with the reported injuries, only the accidental scenario produced a fall which could be described as an 'upturned crucifix', since the push scenario produced a significantly greater body rotation. The witness who alleged that the deceased had been pushed later retracted his statement.

Development of a simulation system for performing in situ surface tests to assess the potential severity of head impacts from alleged childhood short falls

There is considerable debate in the medical literature surrounding the issue of fatal child head injuries being caused by short falls. When reviewing a case history a medical expert will form an opinion of the likely cause of an injury based on his/her knowledge of the literature, training and experience of similar cases. The severity of an injury is determined by the age of the victim, fall height, body impact site and the impact surface. A medical expert, when forming an opinion, is invariably assisted by a description of the scene or scene photographs and assumes the mechanical response of the floor conforms in the same way to "similar" surfaces. The impact response characteristics of the entire surface mixture is critically important when considering the potential for head injury to a child due to a short fall. However, at present during an investigation, the response of a surface to a head impact remains an unknown, since a simple description of, or cursory glance at, a floor surface is insufficient in determining its potential to cause injury. This paper documents the development of a simulation system for assessing the impact response, and potential to cause injury, of domestic floor surfaces during short falls. The method utilises a headform and drop tower adapted from techniques and current standards used to assess the potential for childhood head injuries of playground surfaces and pedestrian-bonnet impacts. The results suggest that the potential of a surface to cause head injury is dependent on the entire surface mixture, including the top surface layer (e.g. carpet and underlay), the underlying surface (wood, chipboard or concrete) and the support material (joists, supports. etc.). The results illustrate a wide range of injury potential between surface mixtures. The simulation system shows the potential to discriminate between differences in surface mixture. In conclusion, the authors suggest that in future investigations, the response of the entire surface mixture be taken into account when forming an opinion on the injury potential of short falls.

Can shaking alone cause fatal brain injury? A biomechanical assessment of the Duhaime shaken baby syndrome model

A biomechanical model of a one-month old baby was designed and tested by Duhaime and co-workers in 1987 in an attempt to assess the biomechanics of the shaken baby syndrome (SBS). The study implied that pure shaking alone cannot cause fatal head injuries, a factor which has been applied in criminal courts. In an attempt to test the validity of the model a preliminary study was undertaken in which a replica was constructed and tested. The broad description of the design and construction of the Duhaime model allowed for variations and therefore uncertainties in its reproduction. It was postulated therefore that differences in certain parameters may increase angular head accelerations. To further investigate this observation, an adjustable replica model was developed and tested. The results indicated that certain parameter changes in the model did in fact lead to an increase in angular head acceleration. When these parameter changes were combined and an injurious shake pattern was employed, using maximum physical effort, the angular head acceleration results exceeded the original Duhaime et al. (1987) results and spanned two scaled tolerance limits for concussion. Additionally, literature suggests that the tolerance limits used to assess the shaking simulation results in the original study may not be reliable. Results from our study were closer to the internal head injury, subdural haematoma, tolerance limits. A series of end point impacts were identified in the shake cycles, therefore, an impact-based head injury measure (Head Injury Criterion - HIC) was utilized to assess their severity. Seven out of ten tests conducted resulted in HIC values exceeding the tolerance limits (critical load value, Stürtz, 1980) suggested for children. At this present stage the authors conclude that it cannot be categorically stated, from a biomechanical perspective, that pure shaking cannot cause fatal head injuries in an infant. Parameters identified in this study require further investigation to assess the accuracy of simulation and increase the biofidelity of the models before further conclusions can be drawn. There must now be sufficient doubt in the reliability of the Duhaime et al. (1987) biomechanical study to warrant the exclusion of such testimony in cases of suspected shaken baby syndrome.

Subdural haemorrhage sustained in a baby-rocker? A biomechanical approach to causation

An unconscious 8 weeks old infant was admitted to hospital and found to have bilateral, subdural and retinal haemorrhages. He died the following day. The explanation for the subdural haemorrhage put forward by his carers was that the infant had been in a baby-rocker and that the carers had seen the rocker being rocked vigorously by their 14 months old daughter on two separate occasions. This paper describes the biomechanics of an infant model in the particular baby-rocker used and determines the maximum forces generated, comparing them with the 'forces' thought to be compatible with the causation of subdural haemorrhage.

The potential and limitations of utilising head impact injury models to assess the likelihood of significant head injury in infants after a fall

The use of engineering principles in assessing head injury scenarios is of increasing significance in investigations into suspected child abuse. A fall scenario is often given as the history for a head injury to an infant. This paper addresses the basic engineering principles and factors to be considered when calculating the severity of a head impact after free-fall. The application of head injury models (HIMs) to ascertain the forces involved in childhood head injuries from impact is also discussed. Previous studies including Duhaime et al. [J. Neurosurg. 66 (1987) 409] and Nokes et al. [Forensic Sci. Int. 79 (1995) 85] have utilised HIMs for this purpose: this paper reviews those models most widely documented.The HIM currently considered the 'state-of-the-art' is the head injury criterion (HIC) and it is suggested that this model should be utilised for assessing head impact injury in child abuse cases where appropriate.