An evaluation of two conducted electrical weapons and two probe designs using a swine comparative cardiac safety model.

Despite human laboratory and field studies that have demonstrated a reasonable safety profile for TASER brand conducted electrical weapons (CEW), the results of some swine studies and arrest related deaths temporal to the use of the CEWs continue to raise questions regarding cardiac safety. TASER International, Inc., has released a new CEW, the TASER X2, touted to have a better safety profile than its long-standing predecessor, the TASER X26. We have developed a model to assess the relative cardiac safety of CEWs and used it to compare the TASER X2 and the TASER X26. This safety model was also used to assess the relative safety of an experimental probe design as compared to the standard steel probe. Our results suggest that the TASER X2 has an improved safety margin over the TASER X26. The new probe design also has promise for enhanced cardiac safety, although may have some disadvantages when compared to the existing design which would make field use impractical.

Use and safety of conducted electronic devices: what is known?

Conductive electronic devices (CED), such as Taser and stun guns, are sold worldwide for use by security services, although they have also been used for self-defence and even for torture. CED are promoted as non-lethal weapons which can potentially save lives. However, there are multiple reports of deaths temporally associated with CED use. These weapons have definite physiological effects in normal volunteers, especially when accompanied by exertion. Medical examiners often report that deaths followed physical encounters which included the use of CED were due to natural causes, excited delirium and/or drug intoxication. These cases present complex situations in which multiple factors potentially contribute to the death, including electric shocks which cause neuromuscular incapacitation, severe pain and anxiety. Public health officials, physicians and hospital personnel need to be aware that individuals controlled with CED are at increased risk of death. We need better recording of incidents worldwide to understand the extent and outcomes of CED use.

Interference of implanted cardiac pacemakers with TASER X26 dart mode application.

The prevalence of pacemaker patients among the general population and of conducted energy devices for law enforcement and self-defence is increasing. Consequently, the question on whether cardiac pacemaker patients are at particular risk becomes increasingly important, in particular, as the widespread use of such devices is planned in Europe. The risk of pacemaker patients has been investigated by numerical simulation at detailed anatomical models of patients with cardiac pacemakers implanted in left pectoral, right pectoral, and abdominal positions, with the monopolar electrode placed at the ventricular apex. The induced cardiac pacemaker interference voltages have been assessed for distant application of TASER X26 devices with dart electrodes propelled towards a subject. It could be shown that interference voltages are highest in abdominal pacemaker implantation, while they are about 20% lower in left or right pectoral sites. They remain below the immunity threshold level as defined by safety standards of implanted cardiac pacemakers and of implanted cardioverter defibrillators to prevent persisting malfunction or damage. However, induced voltages are high enough to be sensed by the pacemaker and to capture pacemaker function in case of hits at thorax and abdomen, frontal as well as dorsal.

Ventricular fibrillation risk estimation for conducted electrical weapons: critical convolutions.

The TASER® Conducted Electrical Weapon (CEW) is used by law enforcement agencies about 900 times per day worldwide and has been shown to reduce suspect and officer injuries by about 65%. However, since a CEW delivers rapid electrical pulses through injected probes, the risk of inducing ventricular fibrillation (VF) has been considered. Animal studies have shown that the tip of the probe must come within a few millimeters of the surface of the heart for the CEW to induce VF in a typical animal application. Early calculations of the CEW VF risk in humans used sophisticated 3-D chest models to determine the size of the probe landing areas that had cardiac tissue within a given distance of the inner surface of the ribs. This produced a distribution of area (cm(2)) vs. mm of depth. Echocardiography was then used to determine the shortest distance from the skin surface to the cardiac surface. This produced a population distribution of skin-to-heart (STH) distances. These 2 distributions were then convolved to arrive at a probability of inducing VF for a typical human CEW application. With 900, 000 probe-mode field uses to date, epidemiological results have shown that these initial VF risk estimates were significant overestimates. We present model refinements that take into account the gender and body-mass-index (BMI) of the target demographics and produce VF risk estimates concordant with the epidemiological results. The risk of VF is estimated at 0.4 per million uses with males.