Measurement of kinetic energy dissipation with gelatine fissure formation with special reference to gelatine validation.

Various methods for calculating the amount of kinetic energy dissipated by a bullet into ballistic gelatine have been suggested in literature. These methods were compared using the results of thirteen 9 mmx19 mm pistol and five 7.62 mmx 39 mm rifle bullets shot into 10% ballistic gelatine. The Wound Profile Method gave the highest correlation, 0.89, with the measured amounts of dissipated kinetic energy. The Fissure surface area and total crack length method gained 0.51 and 0.52, respectively. The experimental results were also compared with those from pig tests with the same bullet types. Using the z-test at 95% level of confidence no difference between impact velocity normalized bullet decelerations could be determined for the 9 mm bullet used. The same test showed significant difference for 7.62 mm bullets. That, however, can be considered to be the result of the bullet's tendency to tumble in non-homogenous living tissue causing significant dispersion of observed deceleration values. The results add further evidence supporting the validity of 10% gelatine at +4 degrees C as wound ballistic tissue simulant. The study also introduces the use of an elastic "shroud" to hold the gelatine in place, to some extent reduce the effects of asymmetric expansion of the gelatine and to simulate the expansion suppression effect of surrounding tissues.

Ballistic skin simulant.

Hydrogels prepared from water solutions containing 10-20 mass% gelatine are generally accepted muscle tissue simulants in terminal ballistic research. They, however, do not have a surface layer which simulates the effect of human skin. The purpose of this research was to find a suitable skin simulant for enhancing the testing fidelity and the credibility of the results with gelatine-based materials when assessing the injury potential of not only high energy bullets, but also especially that of non-penetrating "less lethal" kinetic impact ammunition and relatively low energy ricochet fragments. A skin simulant also permits the simulation and assessment of exit wounds. The mechanical and ballistic properties of human skin and target simulant were established on the basis of results found in the literature. Some errors in these were found. The corrected values are included in this paper for comparison. The target values of the mechanical properties of the skin simulant were the following: threshold velocity v(th)=94+/-4 m/s, tensile strength 18+/-2 N/mm2 and elongation at break 65+/-5%. A selection of synthetic and natural materials was evaluated as skin simulants by analysing their mechanical and ballistic properties. The results were compared to literature values obtained with human cadavers. The tests showed that the best skin simulant of the ones evaluated was semi-finished chrome tanned upholstery "crust" cowhide of 0.9-1.1 mm nominal thickness. Its threshold velocity was 90.7 m/s, tensile strength 20.89+/-4.11 MPa and elongation at break 61+/-9%. These values are the same as the average values of human skin. Of the synthetic materials evaluated, 1mm thick natural rubber can be used on impact side as a threshold velocity filter with some reservations although its theoretical threshold velocity is only 82.9 m/s.

Ballistic variables and tissue devitalisation in penetrating injury--establishing relationship through meta-analysis of a number of pig tests.

BACKGROUND: Assessment of the injury potential is central to ascertaining that a law enforcement bullet does not cause unjustified and excessive injuries. There seems to prevail an understanding that tissue devitalisation correlates with kinetic energy dissipated into the tissue. Other views exist too. The purpose of the study was to find out whether such a correlation can be found and at what level of confidence. METHODS: A number of reported tests done with live pigs with sufficient primary data have first been brought to the same temporally comparable level and then analysed. The tests comprise of 140 shots. To maintain consistency tests with other animals were excluded. RESULTS: The best correlation was obtained between excised muscle tissue and dissipated kinetic energy per millimetre of wound channel. An equation describing the relationship between dissipated energy E(d) and devitalised tissue m(deb) is presented as a regression function m(deb)=44.575xE(d)+10.319 with R2=0.293. An experimental method for estimating the energy used for bullet deformation of controlled deformation bullets is also presented. CONCLUSIONS: A method for using the regression function for obtaining tissue destruction figures for any point of wound channel formed in tissue simulant is presented. The figures are intended for meaningful comparison of the injury potential of various bullets and not for forecasting actual tissue injuries. The documentation of the ballistic properties in animal tests also seems somewhat lacking. Some changes in documenting firearms injuries are proposed in order to validate the methods and further enhance the fidelity of simulant testing.

Preparing ballistic gelatine--review and proposal for a standard method.

Meaningful assessment and comparisons on the injury potentials of various types of ammunition and credible forensic reconstruction require an agreement on standard tissue simulant. Gelatine blocks are relatively inexpensive and easy to produce and they meet most of the criteria for a good terminal ballistic simulant. This research looks into the variables of preparing ballistic gelatine and their effects on penetration resistance. It was found out that consistent quality gelatine blocks are easy to make and that the variables like water temperature have a far smaller effect than previously thought. Also water acidity variances allowed by European Council directive on drinking water do not have any measurable effect. A proposed standard method for gelatine preparation is presented together with penetration function for verification of gelatine quality.

International law and law enforcement firearms.

Several international agreements set constraints on the legitimate use of firearms as representing lethal force. Their meaning in terms of weapons technology must take into account their operational frame of reference, and legitimate warfare can be regarded as a law enforcement operation with similar principles on the use of force. Changes in weapons technology, such as new types of ammunition, transforming firearms into weapons with less-lethal and even humanitarian options, require new interpretations of the legislation. A division into lethal and non-lethal weapons is an oversimplification and the separation of international humanitarian law into military and law enforcement provisions can be questioned from the technical aspect. The type of technology acceptable for law enforcement use of firearms should be defined. An assessment for weapon injury should not be based on lethality, but rather on the potential for tissue damage and its reversibility.