Effects of stun guns and tasers.

contractions and sensory responses, such as various degrees of pain and the feeling of exhaustion. The electrodes are fixed in stun guns but are shot out as darts from tasers. These devices produce electrical stimuli in the form of short-duration (small fraction of a millisecond), repetitive pulses (5–30 pulses/s), each of 50 000 volts. Since currents can be conducted by electrical arcs, effective contact with the body of the person targeted at can be made even if the darts (electrodes) that carry the electrical charge land on thick clothing or if one lands on the ground and the other on the person. The effects of tasers vary greatly, depending on electrical characteristics of the particular device, placement of darts, distance between the darts (a function of the distance from which the gun is fired), and the condition of the person being fired at. In stun guns the electrodes are usually about 5 cm apart, but darts from tasers diverge when fired, and the wider the distance between them when they land on the target, the greater the effect. For example, electrodes 5 cm apart applied directly over the vastus lateralis muscle does not inhibit voluntary function of the muscle during stimulation or afterwards. After about 5 s of application of the stun gun, individuals who have been trying to resist will stop doing so, presumably because of pain or fatigue. By contrast, taser darts placed 10 inches apart (the distance reached if fired from about 6 feet) over the vastus lateralis in the same person will lock the leg in the flexed position, typically leading him or her to surrender quickly. The effects of stun guns have been reported to increase with duration of application. With electrodes 5 cm apart, applications of up to 0·5 s will cause the victim to be startled and repelled. 1–2 s of discharge of current will cause the victim to fall. Falls commonly occur in a slow semi-controlled fashion. The degree of sensation evoked by these devices can result in a response that far outlasts the duration of the current, so discharges of 3–5 s may leave the victim immobilised, dazed, and weak for 5–15 min. In most people a stun gun applied for 4–5 s under the rib cage will bring them to their knees and weaken them. Because of the difference in excitability between nerves and cardiac muscle, and because the heart is distant from the skin, myocardial stimulation is extremely unlikely in normal use of these devices (ie, with darts striking the skin). Studies of the cardiac