Original Communication Are full or empty beer bottles sturdier and does their fracture-threshold suffice to break the human skull? Stephan A. Bolliger MD (Senior Forensic Pathologist) * , Steffen Ross MD (Radiologist), Lars Oesterhelweg MD (Forensic Pathologist), Michael J. Thali MD (Professor, Director, Forensic Pathologist), Beat P. Kneubuehl PhD (Physicist) Centre for Forensic Imaging and Virtopsy, Institute of Forensic Medicine, University of Bern, IRM, Buehlstrasse 20, CH-3012 Bern, Switzerland article info Article history: Received 20 June 2008 Accepted 8 July 2008 Available online 7 November 2008 Keywords: Breaking energy threshold Beer bottles Blunt head trauma abstract Beer bottles are often used in physical disputes. If the bottles break, they may give rise to sharp trauma. However, if the bottles remain intact, they may cause blunt injuries. In order to investigate whether full or empty standard half-litre beer bottles are sturdier and if the necessary breaking energy surpasses the minimum fracture-threshold of the human skull, we tested the fracture properties of such beer bottles in a drop-tower. Full bottles broke at 30 J impact energy, empty bottles at 40 J. These breaking energies surpass the min- imum fracture-threshold of the human neurocranium. Beer bottles may therefore fracture the human skull and therefore serve as dangerous instruments in a physical dispute. Ó 2008 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved. 1. Introduction The examination of living or deceased victims of bar fights is not uncommon in routine forensic practice. These fights are commonly carried out with fists, feet, furniture, and drinking vessels. Depending on the state of the drinking vessels, namely intact or broken, different trauma forms are to be expected. According to a British group, 1 readily available one pint beer glasses such as straight-sided glasses, referred to as nonik, and tankards display a mean impact resistance of up to 1.7 Joule (J). The glass shards of shattered beer glasses may give rise to stab and cut wounds, which may sever blood vessels or other vital structures of the body. Indeed, glasses with lower impact resistance cause more injuries, 2 for which reason toughened glassware has been advocated. On the other hand, if the drinking vessels remain intact, they may serve as clubs. In Switzerland and various other countries, refillable (and therefore sturdy) beer bottles are commonly encountered in pubs and at festivals. In Switzerland, the half-litre, refillable beer bottle is, according to the authors’ own experience, a commonly utilized instrument in physical disputes. The authors have been asked at court whether hitting a human on the head with such intact bottles suffices to break a skull and whether full or empty bottles are more likely to cause such inju- ries. Obviously, this depends on the breaking properties of the bot- tle. If the bottle (full or empty) breaks at a minimal energy, no skull fracture is to be expected. On the other hand, should the stability of the bottle surpass that of the head, severe, even life-threatening injuries may be inflicted. We therefore tested the breaking energy of such beer bottles in a drop-tower as described below in order to estimate at which energies the bottles break and if this amount of energy exceeds the energy necessary to inflict serious injuries to a victim. 2. Methods and materials Ten (six empty and four full) standard 0.5 l beer bottles (Feldschlösschen Brewery, Rheinfelden, Switzerland, Fig. 1) were examined. The full bottles weighed 898 g, the empty ones 391 g. With multislice computed tomography (Somatom Emotion 6, Siemens Medical Solutions, D-91301 Forchheim, Germany) the wall thickness was measured. The minimal thickness was 0.2 cm and maximal thickness 0.36 cm (Fig. 2). To one side of the beer bottles, a 7.5  1.2  5 cm pinewood board was fixed using a thin layer of modelling clay (Fig. 3a). The wood board served to distribute the very small impact point of the steel ball to a more realistic situation concerning the impact area of a beer bottle against a cranium. The modelling clay not only served as a fixing material, but also as a substitute for the soft tis- sues of the scalp. The bottles were then fixed horizontally to the bottom of a baby-bath tub with a thin layer of modelling clay (Fig. 3b). A 1 kg heavy steel ball was dropped from different heights (minimum 2 m, maximum 4 m) onto the beer bottles in a drop- tower specifically designed for the testing of materials (Figs. 4 and 5). 1752-928X/$ - see front matter Ó 2008 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved. doi:10.1016/j.jflm.2008.07.013 * Corresponding author. Tel.: +41 31 631 84 11; fax: +41 31 631 38 33. E-mail address: stephan.bolliger@irm.unibe.ch (S.A. Bolliger). Journal of Forensic and Legal Medicine 16 (2009) 138–142 Contents lists available at ScienceDirect Journal of Forensic and Legal Medicine journal homepage: www.elsevier.com/jflm