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München, Germany

Boss D.,Bayerisches Landeskriminalamt
Proceedings of the AES International Conference

Today, most of the recordings handed in for analysis are digital but there are still cases where analogue tape material has to be investigated. Evidence audio seized from or handed in by private persons has often been recorded in an analogue format, especially on audio cassette recorders or analogue Dictaphones. In cases where an authentication of analogue audio material is required, visualisation of magnetic features is most effective. Visualisation is able to reveal features such as track width and position or shape of head marks. Visualisation adds a dimension to the analysis of audio-tapes that is not present in the oscillogram nor the spectrogram. These show only the phenomena that are within reach of the replay head. Source

Boss D.,Bayerisches Landeskriminalamt
Proceedings of the AES International Conference

Different audio signals can be recorded from the electric circuit. The most important one for analysis purposes in the forensic field is ENF, the electric network frequency: 50 or 60 Hz. On higher frequencies (approximately 110 to 1600 Hz for Germany) one can also find the so-called "ripple signals" - sequences of tones which are used by electric power companies to tele-control electric devices like street lighting or electricity meters (for the change between day and night tariff), etc. Test series that we conducted in different towns in Bavaria showed that ripple signals tend to be stable for a certain location whereas their inter-local variability is very high. This may provide for a possibility of using them for authentication purposes. Copyright © 2012 Audio Engineering Society, Inc. Source

Wasserburger L.,Bayerisches Landeskriminalamt | Eichner S.,Bayerisches Landeskriminalamt | Kunz S.,Ludwig Maximilians University of Munich | Peschel O.,Ludwig Maximilians University of Munich

A comparative study of gas pistols and gas revolvers firing black powder cartridges revealed maximum velocities of 250-300 m/s (v 0.5), corresponding to E max∈=∈0.045 J/ or E max∈= ∈45 mJ and surface area energy concentrations of C∈=∈9-100 mJ/mm 2 for the heaviest gunshot residue (GSR) particles (up to 1 mg). For nitrocellulose cartridges, a velocity of approximately 200-300 m/s (v 0.15), corresponding to 5 mJ for the heaviest GSR particles (0.1 mg) leading to energy concentrations of 25 to >250 mJ/mm 2 could be estimated. Due to these results injuries and in particular eye injuries can be expected. Furthermore a method using paper covered frames was developed so that the wounding potential of different gas weapons and ammunitions can be estimated. In experts opinions the firing distance is of special interest with respect to an accurate estimate of the subjective preconceived injury potential. Reconstruction of real incidents can be useful in casework to estimate firing distances in relation to the severity of injuries. © 2011 Springer-Verlag. Source

Kunz S.N.,University of Salzburg | Kirchhoff S.,Ludwig Maximilians University of Munich | Eggersmann R.,Ludwig Maximilians University of Munich | Stiefel D.,Bayerisches Landeskriminalamt | And 5 more authors.
Journal of Testing and Evaluation

Hunting firearm injuries and fatalities from ricocheted bullets play a minor, but still important, role in forensic medicine and shooting reconstruction. Especially in the area of critical ricochet angles a ballistic analysis is essential to be able to reconstruct hunting accidents. The aim of this study is to analyze ricocheted rifle projectiles (.30-06 Bionic Black and .30-06 Oryx) and shotgun slugs (cal. 12 Brenneke original) from frozen and non-frozen concrete, as well as their ballistic injury potential at a simulated shooting distance of 100m (rifle projectiles) and 20m (slugs). Each projectile had a v100 velocity between 370 m/s (shotgun ammunition) and 740 m/s (rifle ammunition) and was shot at an incident angle between 2-20° (rifle ammunition) and 5-35° (shotgun ammunition). To record the angle of ricochet and target energy of each ricocheted projectile, a polycarbonate wall with a reference scale, as well as ballistic soap were used as a final target. At a shooting distance of 100 m, non-ricochet shots are only possible from high seats, but not from deer stands. The critical shooting angle showed a rather high variation for both rifle and shotgun ammunition and was noted between 1.25 times (shotgun ammunition) and 2.5 times (rifle ammunition) higher for frozen concrete compared to non-frozen concrete. All tested ammunition showed remarkable high variations in the ricochet's angular deviation. Upon the impact of a ricochet, energy levels of over 1000 J were realized with significant injury potential to underlying organs. © VC 2014 by ASTM International. Source

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